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From 0ec0400ef6367812d4f256468ea2adda569baaff Mon Sep 17 00:00:00 2001
Date: Thu, 21 Sep 2023 15:16:04 +0800
Subject: add 8198423-Improve-metaspace-chunk-allocation
---
hotspot/src/share/vm/memory/metachunk.cpp | 93 +-
hotspot/src/share/vm/memory/metachunk.hpp | 93 +-
hotspot/src/share/vm/memory/metaspace.cpp | 1808 ++++++++++++++---
hotspot/src/share/vm/memory/metaspace.hpp | 18 +-
hotspot/src/share/vm/prims/jni.cpp | 4 +-
.../share/vm/utilities/globalDefinitions.hpp | 1 +
6 files changed, 1742 insertions(+), 275 deletions(-)
diff --git a/hotspot/src/share/vm/memory/metachunk.cpp b/hotspot/src/share/vm/memory/metachunk.cpp
index 6cb6625b1..50d0c97eb 100644
--- a/hotspot/src/share/vm/memory/metachunk.cpp
+++ b/hotspot/src/share/vm/memory/metachunk.cpp
@@ -25,6 +25,7 @@
#include "precompiled.hpp"
#include "memory/allocation.hpp"
#include "memory/metachunk.hpp"
+#include "utilities/align.hpp"
#include "utilities/copy.hpp"
#include "utilities/debug.hpp"
@@ -32,8 +33,6 @@ PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
class VirtualSpaceNode;
-const size_t metadata_chunk_initialize = 0xf7f7f7f7;
-
size_t Metachunk::object_alignment() {
// Must align pointers and sizes to 8,
// so that 64 bit types get correctly aligned.
@@ -51,21 +50,22 @@ size_t Metachunk::overhead() {
// Metachunk methods
-Metachunk::Metachunk(size_t word_size,
+Metachunk::Metachunk(ChunkIndex chunktype, bool is_class, size_t word_size,
VirtualSpaceNode* container)
: Metabase<Metachunk>(word_size),
+ _chunk_type(chunktype),
+ _is_class(is_class),
+ _sentinel(CHUNK_SENTINEL),
+ _origin(origin_normal),
+ _use_count(0),
_top(NULL),
_container(container)
{
_top = initial_top();
-#ifdef ASSERT
set_is_tagged_free(false);
- size_t data_word_size = pointer_delta(end(),
- _top,
- sizeof(MetaWord));
- Copy::fill_to_words((HeapWord*)_top,
- data_word_size,
- metadata_chunk_initialize);
+#ifdef ASSERT
+ mangle(uninitMetaWordVal);
+ verify();
#endif
}
@@ -91,33 +91,63 @@ size_t Metachunk::free_word_size() const {
void Metachunk::print_on(outputStream* st) const {
st->print_cr("Metachunk:"
" bottom " PTR_FORMAT " top " PTR_FORMAT
- " end " PTR_FORMAT " size " SIZE_FORMAT,
- bottom(), _top, end(), word_size());
+ " end " PTR_FORMAT " size " SIZE_FORMAT " (%s)",
+ bottom(), _top, end(), word_size(),
+ chunk_size_name(get_chunk_type()));
if (Verbose) {
st->print_cr(" used " SIZE_FORMAT " free " SIZE_FORMAT,
used_word_size(), free_word_size());
}
}
-#ifndef PRODUCT
-void Metachunk::mangle() {
- // Mangle the payload of the chunk and not the links that
+#ifdef ASSERT
+void Metachunk::mangle(juint word_value) {
+ // Overwrite the payload of the chunk and not the links that
// maintain list of chunks.
- HeapWord* start = (HeapWord*)(bottom() + overhead());
+ HeapWord* start = (HeapWord*)initial_top();
size_t size = word_size() - overhead();
- Copy::fill_to_words(start, size, metadata_chunk_initialize);
+ Copy::fill_to_words(start, size, word_value);
}
-#endif // PRODUCT
void Metachunk::verify() {
-#ifdef ASSERT
- // Cannot walk through the blocks unless the blocks have
- // headers with sizes.
- assert(bottom() <= _top &&
- _top <= (MetaWord*)end(),
- "Chunk has been smashed");
-#endif
- return;
+ assert(is_valid_sentinel(), err_msg("Chunk " PTR_FORMAT ": sentinel invalid", p2i(this)));
+ const ChunkIndex chunk_type = get_chunk_type();
+ assert(is_valid_chunktype(chunk_type), err_msg("Chunk " PTR_FORMAT ": Invalid chunk type.", p2i(this)));
+ if (chunk_type != HumongousIndex) {
+ assert(word_size() == get_size_for_nonhumongous_chunktype(chunk_type, is_class()),
+ err_msg("Chunk " PTR_FORMAT ": wordsize " SIZE_FORMAT " does not fit chunk type %s.",
+ p2i(this), word_size(), chunk_size_name(chunk_type)));
+ }
+ assert(is_valid_chunkorigin(get_origin()), err_msg("Chunk " PTR_FORMAT ": Invalid chunk origin.", p2i(this)));
+ assert(bottom() <= _top && _top <= (MetaWord*)end(),
+ err_msg("Chunk " PTR_FORMAT ": Chunk top out of chunk bounds.", p2i(this)));
+
+ // For non-humongous chunks, starting address shall be aligned
+ // to its chunk size. Humongous chunks start address is
+ // aligned to specialized chunk size.
+ const size_t required_alignment =
+ (chunk_type != HumongousIndex ? word_size() : get_size_for_nonhumongous_chunktype(SpecializedIndex, is_class())) * sizeof(MetaWord);
+ assert(is_aligned((address)this, required_alignment),
+ err_msg("Chunk " PTR_FORMAT ": (size " SIZE_FORMAT ") not aligned to " SIZE_FORMAT ".",
+ p2i(this), word_size() * sizeof(MetaWord), required_alignment));
+}
+
+#endif // ASSERT
+
+// Helper, returns a descriptive name for the given index.
+const char* chunk_size_name(ChunkIndex index) {
+ switch (index) {
+ case SpecializedIndex:
+ return "specialized";
+ case SmallIndex:
+ return "small";
+ case MediumIndex:
+ return "medium";
+ case HumongousIndex:
+ return "humongous";
+ default:
+ return "Invalid index";
+ }
}
/////////////// Unit tests ///////////////
@@ -127,11 +157,16 @@ void Metachunk::verify() {
class TestMetachunk {
public:
static void test() {
- size_t size = 2 * 1024 * 1024;
- void* memory = malloc(size);
+ const ChunkIndex chunk_type = MediumIndex;
+ const bool is_class = false;
+ const size_t word_size = get_size_for_nonhumongous_chunktype(chunk_type, is_class);
+ // Allocate the chunk with correct alignment.
+ void* memory = malloc(word_size * BytesPerWord * 2);
assert(memory != NULL, "Failed to malloc 2MB");
+
+ void* p_placement = align_up(memory, word_size * BytesPerWord);
- Metachunk* metachunk = ::new (memory) Metachunk(size / BytesPerWord, NULL);
+ Metachunk* metachunk = ::new (p_placement) Metachunk(chunk_type, is_class, word_size, NULL);
assert(metachunk->bottom() == (MetaWord*)metachunk, "assert");
assert(metachunk->end() == (uintptr_t*)metachunk + metachunk->size(), "assert");
diff --git a/hotspot/src/share/vm/memory/metachunk.hpp b/hotspot/src/share/vm/memory/metachunk.hpp
index 7889b622c..b679f1b1e 100644
--- a/hotspot/src/share/vm/memory/metachunk.hpp
+++ b/hotspot/src/share/vm/memory/metachunk.hpp
@@ -94,6 +94,61 @@ class Metabase VALUE_OBJ_CLASS_SPEC {
// | | | |
// +--------------+ <- bottom --+ --+
+// ChunkIndex defines the type of chunk.
+// Chunk types differ by size: specialized < small < medium, chunks
+// larger than medium are humongous chunks of varying size.
+enum ChunkIndex {
+ ZeroIndex = 0,
+ SpecializedIndex = ZeroIndex,
+ SmallIndex = SpecializedIndex + 1,
+ MediumIndex = SmallIndex + 1,
+ HumongousIndex = MediumIndex + 1,
+ NumberOfFreeLists = 3,
+ NumberOfInUseLists = 4
+};
+
+// Utility functions.
+size_t get_size_for_nonhumongous_chunktype(ChunkIndex chunk_type, bool is_class);
+ChunkIndex get_chunk_type_by_size(size_t size, bool is_class);
+
+// Returns a descriptive name for a chunk type.
+const char* chunk_size_name(ChunkIndex index);
+
+// Verify chunk type.
+inline bool is_valid_chunktype(ChunkIndex index) {
+ return index == SpecializedIndex || index == SmallIndex ||
+ index == MediumIndex || index == HumongousIndex;
+}
+
+inline bool is_valid_nonhumongous_chunktype(ChunkIndex index) {
+ return is_valid_chunktype(index) && index != HumongousIndex;
+}
+
+enum ChunkOrigin {
+ // Chunk normally born (via take_from_committed)
+ origin_normal = 1,
+ // Chunk was born as padding chunk
+ origin_pad = 2,
+ // Chunk was born as leftover chunk in VirtualSpaceNode::retire
+ origin_leftover = 3,
+ // Chunk was born as result of a merge of smaller chunks
+ origin_merge = 4,
+ // Chunk was born as result of a split of a larger chunk
+ origin_split = 5,
+
+ origin_minimum = origin_normal,
+ origin_maximum = origin_split,
+ origins_count = origin_maximum + 1
+};
+
+inline bool is_valid_chunkorigin(ChunkOrigin origin) {
+ return origin == origin_normal ||
+ origin == origin_pad ||
+ origin == origin_leftover ||
+ origin == origin_merge ||
+ origin == origin_split;
+}
+
class Metachunk : public Metabase<Metachunk> {
friend class TestMetachunk;
// The VirtualSpaceNode containing this chunk.
@@ -102,8 +157,21 @@ class Metachunk : public Metabase<Metachunk> {
// Current allocation top.
MetaWord* _top;
- DEBUG_ONLY(bool _is_tagged_free;)
+ // A 32bit sentinel for debugging purposes.
+ enum { CHUNK_SENTINEL = 0x4d4554EF, // "MET"
+ CHUNK_SENTINEL_INVALID = 0xFEEEEEEF
+ };
+
+ uint32_t _sentinel;
+ const ChunkIndex _chunk_type;
+ const bool _is_class;
+ // Whether the chunk is free (in freelist) or in use by some class loader.
+ bool _is_tagged_free;
+
+ ChunkOrigin _origin;
+ int _use_count;
+
MetaWord* initial_top() const { return (MetaWord*)this + overhead(); }
MetaWord* top() const { return _top; }
@@ -120,7 +188,7 @@ class Metachunk : public Metabase<Metachunk> {
// Size of the Metachunk header, including alignment.
static size_t overhead();
- Metachunk(size_t word_size , VirtualSpaceNode* container);
+ Metachunk(ChunkIndex chunktype, bool is_class, size_t word_size, VirtualSpaceNode* container);
MetaWord* allocate(size_t word_size);
@@ -140,17 +208,28 @@ class Metachunk : public Metabase<Metachunk> {
size_t used_word_size() const;
size_t free_word_size() const;
-#ifdef ASSERT
bool is_tagged_free() { return _is_tagged_free; }
void set_is_tagged_free(bool v) { _is_tagged_free = v; }
-#endif
bool contains(const void* ptr) { return bottom() <= ptr && ptr < _top; }
- NOT_PRODUCT(void mangle();)
-
void print_on(outputStream* st) const;
- void verify();
+
+ bool is_valid_sentinel() const { return _sentinel == CHUNK_SENTINEL; }
+ void remove_sentinel() { _sentinel = CHUNK_SENTINEL_INVALID; }
+
+ int get_use_count() const { return _use_count; }
+ void inc_use_count() { _use_count ++; }
+
+ ChunkOrigin get_origin() const { return _origin; }
+ void set_origin(ChunkOrigin orig) { _origin = orig; }
+
+ ChunkIndex get_chunk_type() const { return _chunk_type; }
+ bool is_class() const { return _is_class; }
+
+ DEBUG_ONLY(void mangle(juint word_value);)
+ DEBUG_ONLY(void verify();)
+
};
// Metablock is the unit of allocation from a Chunk.
diff --git a/hotspot/src/share/vm/memory/metaspace.cpp b/hotspot/src/share/vm/memory/metaspace.cpp
index cc5bd4544..07259e649 100644
--- a/hotspot/src/share/vm/memory/metaspace.cpp
+++ b/hotspot/src/share/vm/memory/metaspace.cpp
@@ -46,6 +46,7 @@
#include "runtime/orderAccess.inline.hpp"
#include "services/memTracker.hpp"
#include "services/memoryService.hpp"
+#include "utilities/align.hpp"
#include "utilities/copy.hpp"
#include "utilities/debug.hpp"
@@ -57,6 +58,13 @@ typedef BinaryTreeDictionary<Metachunk, FreeList<Metachunk> > ChunkTreeDictionar
// Set this constant to enable slow integrity checking of the free chunk lists
const bool metaspace_slow_verify = false;
+// Helper function that does a bunch of checks for a chunk.
+DEBUG_ONLY(static void do_verify_chunk(Metachunk* chunk);)
+
+// Given a Metachunk, update its in-use information (both in the
+// chunk and the occupancy map).
+static void do_update_in_use_info_for_chunk(Metachunk* chunk, bool inuse);
+
size_t const allocation_from_dictionary_limit = 4 * K;
MetaWord* last_allocated = 0;
@@ -64,33 +72,6 @@ MetaWord* last_allocated = 0;
size_t Metaspace::_compressed_class_space_size;
const MetaspaceTracer* Metaspace::_tracer = NULL;
-// Used in declarations in SpaceManager and ChunkManager
-enum ChunkIndex {
- ZeroIndex = 0,
- SpecializedIndex = ZeroIndex,
- SmallIndex = SpecializedIndex + 1,
- MediumIndex = SmallIndex + 1,
- HumongousIndex = MediumIndex + 1,
- NumberOfFreeLists = 3,
- NumberOfInUseLists = 4
-};
-
-// Helper, returns a descriptive name for the given index.
-static const char* chunk_size_name(ChunkIndex index) {
- switch (index) {
- case SpecializedIndex:
- return "specialized";
- case SmallIndex:
- return "small";
- case MediumIndex:
- return "medium";
- case HumongousIndex:
- return "humongous";
- default:
- return "Invalid index";
- }
-}
-
enum ChunkSizes { // in words.
ClassSpecializedChunk = 128,
SpecializedChunk = 128,
@@ -100,11 +81,69 @@ enum ChunkSizes { // in words.
MediumChunk = 8 * K
};
+// Returns size of this chunk type.
+size_t get_size_for_nonhumongous_chunktype(ChunkIndex chunktype, bool is_class) {
+ assert(is_valid_nonhumongous_chunktype(chunktype), "invalid chunk type.");
+ size_t size = 0;
+ if (is_class) {
+ switch(chunktype) {
+ case SpecializedIndex: size = ClassSpecializedChunk; break;
+ case SmallIndex: size = ClassSmallChunk; break;
+ case MediumIndex: size = ClassMediumChunk; break;
+ default:
+ ShouldNotReachHere();
+ }
+ } else {
+ switch(chunktype) {
+ case SpecializedIndex: size = SpecializedChunk; break;
+ case SmallIndex: size = SmallChunk; break;
+ case MediumIndex: size = MediumChunk; break;
+ default:
+ ShouldNotReachHere();
+ }
+ }
+ return size;
+}
+
+ChunkIndex get_chunk_type_by_size(size_t size, bool is_class) {
+ if (is_class) {
+ if (size == ClassSpecializedChunk) {
+ return SpecializedIndex;
+ } else if (size == ClassSmallChunk) {
+ return SmallIndex;
+ } else if (size == ClassMediumChunk) {
+ return MediumIndex;
+ } else if (size > ClassMediumChunk) {
+ assert(is_aligned(size, ClassSpecializedChunk), "Invalid chunk size");
+ return HumongousIndex;
+ }
+ } else {
+ if (size == SpecializedChunk) {
+ return SpecializedIndex;
+ } else if (size == SmallChunk) {
+ return SmallIndex;
+ } else if (size == MediumChunk) {
+ return MediumIndex;
+ } else if (size > MediumChunk) {
+ assert(is_aligned(size, SpecializedChunk), "Invalid chunk size");
+ return HumongousIndex;
+ }
+ }
+ ShouldNotReachHere();
+ return (ChunkIndex)-1;
+}
+
+
static ChunkIndex next_chunk_index(ChunkIndex i) {
assert(i < NumberOfInUseLists, "Out of bound");
return (ChunkIndex) (i+1);
}
+static ChunkIndex prev_chunk_index(ChunkIndex i) {
+ assert(i > ZeroIndex, "Out of bound");
+ return (ChunkIndex) (i-1);
+}
+
static const char* scale_unit(size_t scale) {
switch(scale) {
case 1: return "BYTES";
@@ -131,24 +170,33 @@ class ChunkManager : public CHeapObj<mtInternal> {
// SpecializedChunk
// SmallChunk
// MediumChunk
- // HumongousChunk
ChunkList _free_chunks[NumberOfFreeLists];
+ // Whether or not this is the class chunkmanager.
+ const bool _is_class;
+
+ // Return non-humongous chunk list by its index.
+ ChunkList* free_chunks(ChunkIndex index);
+
+ // Returns non-humongous chunk list for the given chunk word size.
+ ChunkList* find_free_chunks_list(size_t word_size);
+
// HumongousChunk
ChunkTreeDictionary _humongous_dictionary;
- // ChunkManager in all lists of this type
+ // Returns the humongous chunk dictionary.
+ ChunkTreeDictionary* humongous_dictionary() {
+ return &_humongous_dictionary;
+ }
+
+ // Size, in metaspace words, of all chunks managed by this ChunkManager
size_t _free_chunks_total;
+ // Number of chunks in this ChunkManager
size_t _free_chunks_count;
- void dec_free_chunks_total(size_t v) {
- assert(_free_chunks_count > 0 &&
- _free_chunks_total > 0,
- "About to go negative");
- Atomic::add_ptr(-1, &_free_chunks_count);
- jlong minus_v = (jlong) - (jlong) v;
- Atomic::add_ptr(minus_v, &_free_chunks_total);
- }
+ // Update counters after a chunk was added or removed removed.
+ void account_for_added_chunk(const Metachunk* c);
+ void account_for_removed_chunk(const Metachunk* c);
// Debug support
@@ -169,6 +217,29 @@ class ChunkManager : public CHeapObj<mtInternal> {
}
void verify_free_chunks_count();
+ // Given a pointer to a chunk, attempts to merge it with neighboring
+ // free chunks to form a bigger chunk. Returns true if successful.
+ bool attempt_to_coalesce_around_chunk(Metachunk* chunk, ChunkIndex target_chunk_type);
+
+ // Helper for chunk merging:
+ // Given an address range with 1-n chunks which are all supposed to be
+ // free and hence currently managed by this ChunkManager, remove them
+ // from this ChunkManager and mark them as invalid.
+ // - This does not correct the occupancy map.
+ // - This does not adjust the counters in ChunkManager.
+ // - Does not adjust container count counter in containing VirtualSpaceNode.
+ // Returns number of chunks removed.
+ int remove_chunks_in_area(MetaWord* p, size_t word_size);
+
+ // Helper for chunk splitting: given a target chunk size and a larger free chunk,
+ // split up the larger chunk into n smaller chunks, at least one of which should be
+ // the target chunk of target chunk size. The smaller chunks, including the target
+ // chunk, are returned to the freelist. The pointer to the target chunk is returned.
+ // Note that this chunk is supposed to be removed from the freelist right away.
+ Metachunk* split_chunk(size_t target_chunk_word_size, Metachunk* chunk);
+
+ public:
+
struct ChunkManagerStatistics {
size_t num_by_type[NumberOfFreeLists];
size_t single_size_by_type[NumberOfFreeLists];
@@ -181,16 +252,15 @@ class ChunkManager : public CHeapObj<mtInternal> {
void get_statistics(ChunkManagerStatistics* stat) const;
static void print_statistics(const ChunkManagerStatistics* stat, outputStream* out, size_t scale);
- public:
- ChunkManager(size_t specialized_size, size_t small_size, size_t medium_size)
- : _free_chunks_total(0), _free_chunks_count(0) {
- _free_chunks[SpecializedIndex].set_size(specialized_size);
- _free_chunks[SmallIndex].set_size(small_size);
- _free_chunks[MediumIndex].set_size(medium_size);
+ ChunkManager(bool is_class)
+ : _is_class(is_class), _free_chunks_total(0), _free_chunks_count(0) {
+ _free_chunks[SpecializedIndex].set_size(get_size_for_nonhumongous_chunktype(SpecializedIndex, is_class));
+ _free_chunks[SmallIndex].set_size(get_size_for_nonhumongous_chunktype(SmallIndex, is_class));
+ _free_chunks[MediumIndex].set_size(get_size_for_nonhumongous_chunktype(MediumIndex, is_class));
}
- // add or delete (return) a chunk to the global freelist.
+ // Add or delete (return) a chunk to the global freelist.
Metachunk* chunk_freelist_allocate(size_t word_size);
// Map a size to a list index assuming that there are lists
@@ -200,13 +270,24 @@ class ChunkManager : public CHeapObj<mtInternal> {
// Map a given index to the chunk size.
size_t size_by_index(ChunkIndex index) const;
- // Remove the chunk from its freelist. It is
- // expected to be on one of the _free_chunks[] lists.
+ bool is_class() const { return _is_class; }
+
+ // Convenience accessors.
+ size_t medium_chunk_word_size() const { return size_by_index(MediumIndex); }
+ size_t small_chunk_word_size() const { return size_by_index(SmallIndex); }
+ size_t specialized_chunk_word_size() const { return size_by_index(SpecializedIndex); }
+
+ // Take a chunk from the ChunkManager. The chunk is expected to be in
+ // the chunk manager (the freelist if non-humongous, the dictionary if
+ // humongous).
void remove_chunk(Metachunk* chunk);
+ // Return a single chunk of type index to the ChunkManager.
+ void return_single_chunk(ChunkIndex index, Metachunk* chunk);
+
// Add the simple linked list of chunks to the freelist of chunks
// of type index.
- void return_chunks(ChunkIndex index, Metachunk* chunks);
+ void return_chunk_list(ChunkIndex index, Metachunk* chunk);
// Total of the space in the free chunks list
size_t free_chunks_total_words();
@@ -215,19 +296,6 @@ class ChunkManager : public CHeapObj<mtInternal> {
// Number of chunks in the free chunks list
size_t free_chunks_count();
- void inc_free_chunks_total(size_t v, size_t count = 1) {
- Atomic::add_ptr(count, &_free_chunks_count);
- Atomic::add_ptr(v, &_free_chunks_total);
- }
- ChunkTreeDictionary* humongous_dictionary() {
- return &_humongous_dictionary;
- }
-
- ChunkList* free_chunks(ChunkIndex index);
-
- // Returns the list for the given chunk word size.
- ChunkList* find_free_chunks_list(size_t word_size);
-
// Remove from a list by size. Selects list based on size of chunk.
Metachunk* free_chunks_get(size_t chunk_word_size);
@@ -329,6 +397,294 @@ class BlockFreelist VALUE_OBJ_CLASS_SPEC {
void print_on(outputStream* st) const;
};
+// Helper for Occupancy Bitmap. A type trait to give an all-bits-are-one-unsigned constant.
+template <typename T> struct all_ones { static const T value; };
+template <> struct all_ones <uint64_t> { static const uint64_t value = 0xFFFFFFFFFFFFFFFFULL; };
+template <> struct all_ones <uint32_t> { static const uint32_t value = 0xFFFFFFFF; };
+
+// The OccupancyMap is a bitmap which, for a given VirtualSpaceNode,
+// keeps information about
+// - where a chunk starts
+// - whether a chunk is in-use or free
+// A bit in this bitmap represents one range of memory in the smallest
+// chunk size (SpecializedChunk or ClassSpecializedChunk).
+class OccupancyMap : public CHeapObj<mtInternal> {
+
+ // The address range this map covers.
+ const MetaWord* const _reference_address;
+ const size_t _word_size;
+
+ // The word size of a specialized chunk, aka the number of words one
+ // bit in this map represents.
+ const size_t _smallest_chunk_word_size;
+
+ // map data
+ // Data are organized in two bit layers:
+ // The first layer is the chunk-start-map. Here, a bit is set to mark
+ // the corresponding region as the head of a chunk.
+ // The second layer is the in-use-map. Here, a set bit indicates that
+ // the corresponding belongs to a chunk which is in use.
+ uint8_t* _map[2];
+
+ enum { layer_chunk_start_map = 0, layer_in_use_map = 1 };
+
+ // length, in bytes, of bitmap data
+ size_t _map_size;
+
+ // Returns true if bit at position pos at bit-layer layer is set.
+ bool get_bit_at_position(unsigned pos, unsigned layer) const {
+ assert(layer == 0 || layer == 1, err_msg("Invalid layer %d", layer));
+ const unsigned byteoffset = pos / 8;
+ assert(byteoffset < _map_size,
+ err_msg("invalid byte offset (%u), map size is " SIZE_FORMAT ".", byteoffset, _map_size));
+ const unsigned mask = 1 << (pos % 8);
+ return (_map[layer][byteoffset] & mask) > 0;
+ }
+
+ // Changes bit at position pos at bit-layer layer to value v.
+ void set_bit_at_position(unsigned pos, unsigned layer, bool v) {
+ assert(layer == 0 || layer == 1, err_msg("Invalid layer %d", layer));
+ const unsigned byteoffset = pos / 8;
+ assert(byteoffset < _map_size,
+ err_msg("invalid byte offset (%u), map size is " SIZE_FORMAT ".", byteoffset, _map_size));
+ const unsigned mask = 1 << (pos % 8);
+ if (v) {
+ _map[layer][byteoffset] |= mask;
+ } else {
+ _map[layer][byteoffset] &= ~mask;
+ }
+ }
+
+ // Optimized case of is_any_bit_set_in_region for 32/64bit aligned access:
+ // pos is 32/64 aligned and num_bits is 32/64.
+ // This is the typical case when coalescing to medium chunks, whose size is
+ // 32 or 64 times the specialized chunk size (depending on class or non class
+ // case), so they occupy 64 bits which should be 64bit aligned, because
+ // chunks are chunk-size aligned.
+ template <typename T>
+ bool is_any_bit_set_in_region_3264(unsigned pos, unsigned num_bits, unsigned layer) const {
+ assert(_map_size > 0, "not initialized");
+ assert(layer == 0 || layer == 1, err_msg("Invalid layer %d.", layer));
+ assert(pos % (sizeof(T) * 8) == 0, err_msg("Bit position must be aligned (%u).", pos));
+ assert(num_bits == (sizeof(T) * 8), err_msg("Number of bits incorrect (%u).", num_bits));
+ const size_t byteoffset = pos / 8;
+ assert(byteoffset <= (_map_size - sizeof(T)),
+ err_msg("Invalid byte offset (" SIZE_FORMAT "), map size is " SIZE_FORMAT ".", byteoffset, _map_size));
+ const T w = *(T*)(_map[layer] + byteoffset);
+ return w > 0 ? true : false;
+ }
+
+ // Returns true if any bit in region [pos1, pos1 + num_bits) is set in bit-layer layer.
+ bool is_any_bit_set_in_region(unsigned pos, unsigned num_bits, unsigned layer) const {
+ if (pos % 32 == 0 && num_bits == 32) {
+ return is_any_bit_set_in_region_3264<uint32_t>(pos, num_bits, layer);
+ } else if (pos % 64 == 0 && num_bits == 64) {
+ return is_any_bit_set_in_region_3264<uint64_t>(pos, num_bits, layer);
+ } else {
+ for (unsigned n = 0; n < num_bits; n ++) {
+ if (get_bit_at_position(pos + n, layer)) {
+ return true;
+ }
+ }
+ }
+ return false;
+ }
+
+ // Returns true if any bit in region [p, p+word_size) is set in bit-layer layer.
+ bool is_any_bit_set_in_region(MetaWord* p, size_t word_size, unsigned layer) const {
+ assert(word_size % _smallest_chunk_word_size == 0,
+ err_msg("Region size " SIZE_FORMAT " not a multiple of smallest chunk size.", word_size));
+ const unsigned pos = get_bitpos_for_address(p);
+ const unsigned num_bits = (unsigned) (word_size / _smallest_chunk_word_size);
+ return is_any_bit_set_in_region(pos, num_bits, layer);
+ }
+
+ // Optimized case of set_bits_of_region for 32/64bit aligned access:
+ // pos is 32/64 aligned and num_bits is 32/64.
+ // This is the typical case when coalescing to medium chunks, whose size
+ // is 32 or 64 times the specialized chunk size (depending on class or non
+ // class case), so they occupy 64 bits which should be 64bit aligned,
+ // because chunks are chunk-size aligned.
+ template <typename T>
+ void set_bits_of_region_T(unsigned pos, unsigned num_bits, unsigned layer, bool v) {
+ assert(pos % (sizeof(T) * 8) == 0, err_msg("Bit position must be aligned to %u (%u).",
+ (unsigned)(sizeof(T) * 8), pos));
+ assert(num_bits == (sizeof(T) * 8), err_msg("Number of bits incorrect (%u), expected %u.",
+ num_bits, (unsigned)(sizeof(T) * 8)));
+ const size_t byteoffset = pos / 8;
+ assert(byteoffset <= (_map_size - sizeof(T)),
+ err_msg("invalid byte offset (" SIZE_FORMAT "), map size is " SIZE_FORMAT ".", byteoffset, _map_size));
+ T* const pw = (T*)(_map[layer] + byteoffset);
+ *pw = v ? all_ones<T>::value : (T) 0;
+ }
+
+ // Set all bits in a region starting at pos to a value.
+ void set_bits_of_region(unsigned pos, unsigned num_bits, unsigned layer, bool v) {
+ assert(_map_size > 0, "not initialized");
+ assert(layer == 0 || layer == 1, err_msg("Invalid layer %d.", layer));
+ if (pos % 32 == 0 && num_bits == 32) {
+ set_bits_of_region_T<uint32_t>(pos, num_bits, layer, v);
+ } else if (pos % 64 == 0 && num_bits == 64) {
+ set_bits_of_region_T<uint64_t>(pos, num_bits, layer, v);
+ } else {
+ for (unsigned n = 0; n < num_bits; n ++) {
+ set_bit_at_position(pos + n, layer, v);
+ }
+ }
+ }
+
+ // Helper: sets all bits in a region [p, p+word_size).
+ void set_bits_of_region(MetaWord* p, size_t word_size, unsigned layer, bool v) {
+ assert(word_size % _smallest_chunk_word_size == 0,
+ err_msg("Region size " SIZE_FORMAT " not a multiple of smallest chunk size.", word_size));
+ const unsigned pos = get_bitpos_for_address(p);
+ const unsigned num_bits = (unsigned) (word_size / _smallest_chunk_word_size);
+ set_bits_of_region(pos, num_bits, layer, v);
+ }
+
+ // Helper: given an address, return the bit position representing that address.
+ unsigned get_bitpos_for_address(const MetaWord* p) const {
+ assert(_reference_address != NULL, "not initialized");
+ assert(p >= _reference_address && p < _reference_address + _word_size,
+ err_msg("Address %p out of range for occupancy map [%p..%p).",
+ p, _reference_address, _reference_address + _word_size));
+ assert(is_aligned(p, _smallest_chunk_word_size * sizeof(MetaWord)),
+ err_msg("Address not aligned (%p).", p));
+ const ptrdiff_t d = (p - _reference_address) / _smallest_chunk_word_size;
+ assert(d >= 0 && (size_t)d < _map_size * 8, "Sanity.");
+ return (unsigned) d;
+ }
+
+ public:
+
+ OccupancyMap(const MetaWord* reference_address, size_t word_size, size_t smallest_chunk_word_size) :
+ _reference_address(reference_address), _word_size(word_size),
+ _smallest_chunk_word_size(smallest_chunk_word_size) {
+ assert(reference_address != NULL, "invalid reference address");
+ assert(is_aligned(reference_address, smallest_chunk_word_size),
+ "Reference address not aligned to smallest chunk size.");
+ assert(is_aligned(word_size, smallest_chunk_word_size),
+ "Word_size shall be a multiple of the smallest chunk size.");
+ // Calculate bitmap size: one bit per smallest_chunk_word_size'd area.
+ size_t num_bits = word_size / smallest_chunk_word_size;
+ _map_size = (num_bits + 7) / 8;
+ assert(_map_size * 8 >= num_bits, "sanity");
+ _map[0] = (uint8_t*) os::malloc(_map_size, mtInternal);
+ _map[1] = (uint8_t*) os::malloc(_map_size, mtInternal);
+ assert(_map[0] != NULL && _map[1] != NULL, "Occupancy Map: allocation failed.");
+ memset(_map[1], 0, _map_size);
+ memset(_map[0], 0, _map_size);
+ // Sanity test: the first respectively last possible chunk start address in
+ // the covered range shall map to the first and last bit in the bitmap.
+ assert(get_bitpos_for_address(reference_address) == 0,
+ "First chunk address in range must map to fist bit in bitmap.");
+ assert(get_bitpos_for_address(reference_address + word_size - smallest_chunk_word_size) == num_bits - 1,
+ "Last chunk address in range must map to last bit in bitmap.");
+ }
+
+ ~OccupancyMap() {
+ os::free(_map[0]);
+ os::free(_map[1]);
+ }
+
+ // Returns true if at address x a chunk is starting.
+ bool chunk_starts_at_address(MetaWord* p) const {
+ const unsigned pos = get_bitpos_for_address(p);
+ return get_bit_at_position(pos, layer_chunk_start_map);
+ }
+
+ void set_chunk_starts_at_address(MetaWord* p, bool v) {
+ const unsigned pos = get_bitpos_for_address(p);
+ set_bit_at_position(pos, layer_chunk_start_map, v);
+ }
+
+ // Removes all chunk-start-bits inside a region, typically as a
+ // result of a chunk merge.
+ void wipe_chunk_start_bits_in_region(MetaWord* p, size_t word_size) {
+ set_bits_of_region(p, word_size, layer_chunk_start_map, false);
+ }
+
+ // Returns true if there are life (in use) chunks in the region limited
+ // by [p, p+word_size).
+ bool is_region_in_use(MetaWord* p, size_t word_size) const {
+ return is_any_bit_set_in_region(p, word_size, layer_in_use_map);
+ }
+
+ // Marks the region starting at p with the size word_size as in use
+ // or free, depending on v.
+ void set_region_in_use(MetaWord* p, size_t word_size, bool v) {
+ set_bits_of_region(p, word_size, layer_in_use_map, v);
+ }
+
+#ifdef ASSERT
+ // Verify occupancy map for the address range [from, to).
+ // We need to tell it the address range, because the memory the
+ // occupancy map is covering may not be fully comitted yet.
+ void verify(MetaWord* from, MetaWord* to) {
+ Metachunk* chunk = NULL;
+ int nth_bit_for_chunk = 0;
+ MetaWord* chunk_end = NULL;
+ for (MetaWord* p = from; p < to; p += _smallest_chunk_word_size) {
+ const unsigned pos = get_bitpos_for_address(p);
+ // Check the chunk-starts-info:
+ if (get_bit_at_position(pos, layer_chunk_start_map)) {
+ // Chunk start marked in bitmap.
+ chunk = (Metachunk*) p;
+ if (chunk_end != NULL) {
+ assert(chunk_end == p, err_msg("Unexpected chunk start found at %p (expected "
+ "the next chunk to start at %p).", p, chunk_end));
+ }
+ assert(chunk->is_valid_sentinel(), err_msg("Invalid chunk at address %p.", p));
+ if (chunk->get_chunk_type() != HumongousIndex) {
+ guarantee(is_aligned(p, chunk->word_size()), err_msg("Chunk %p not aligned.", p));
+ }
+ chunk_end = p + chunk->word_size();
+ nth_bit_for_chunk = 0;
+ assert(chunk_end <= to, "Chunk end overlaps test address range.");
+ } else {
+ // No chunk start marked in bitmap.
+ assert(chunk != NULL, "Chunk should start at start of address range.");
+ assert(p < chunk_end, err_msg("Did not find expected chunk start at %p.", p));
+ nth_bit_for_chunk ++;
+ }
+ // Check the in-use-info:
+ const bool in_use_bit = get_bit_at_position(pos, layer_in_use_map);
+ if (in_use_bit) {
+ assert(!chunk->is_tagged_free(), err_msg("Chunk %p: marked in-use in map but is free (bit %u).",
+ chunk, nth_bit_for_chunk));
+ } else {
+ assert(chunk->is_tagged_free(), err_msg("Chunk %p: marked free in map but is in use (bit %u).",
+ chunk, nth_bit_for_chunk));
+ }
+ }
+ }
+
+ // Verify that a given chunk is correctly accounted for in the bitmap.
+ void verify_for_chunk(Metachunk* chunk) {
+ assert(chunk_starts_at_address((MetaWord*) chunk),
+ err_msg("No chunk start marked in map for chunk %p.", chunk));
+ // For chunks larger than the minimal chunk size, no other chunk
+ // must start in its area.
+ if (chunk->word_size() > _smallest_chunk_word_size) {
+ assert(!is_any_bit_set_in_region(((MetaWord*) chunk) + _smallest_chunk_word_size,
+ chunk->word_size() - _smallest_chunk_word_size, layer_chunk_start_map),
+ "No chunk must start within another chunk.");
+ }
+ if (!chunk->is_tagged_free()) {
+ assert(is_region_in_use((MetaWord*)chunk, chunk->word_size()),
+ err_msg("Chunk %p is in use but marked as free in map (%d %d).",
+ chunk, chunk->get_chunk_type(), chunk->get_origin()));
+ } else {
+ assert(!is_region_in_use((MetaWord*)chunk, chunk->word_size()),
+ err_msg("Chunk %p is free but marked as in-use in map (%d %d).",
+ chunk, chunk->get_chunk_type(), chunk->get_origin()));
+ }
+ }
+
+#endif // ASSERT
+
+};
+
// A VirtualSpaceList node.
class VirtualSpaceNode : public CHeapObj<mtClass> {
friend class VirtualSpaceList;
@@ -336,6 +692,9 @@ class VirtualSpaceNode : public CHeapObj<mtClass> {
// Link to next VirtualSpaceNode
VirtualSpaceNode* _next;
+ // Whether this node is contained in class or metaspace.
+ const bool _is_class;
+
// total in the VirtualSpace
MemRegion _reserved;
ReservedSpace _rs;
@@ -344,6 +703,8 @@ class VirtualSpaceNode : public CHeapObj<mtClass> {
// count of chunks contained in this VirtualSpace
uintx _container_count;
+ OccupancyMap* _occupancy_map;
+
// Convenience functions to access the _virtual_space
char* low() const { return virtual_space()->low(); }
char* high() const { return virtual_space()->high(); }
@@ -354,16 +715,28 @@ class VirtualSpaceNode : public CHeapObj<mtClass> {
// Committed but unused space in the virtual space
size_t free_words_in_vs() const;
+
+ // True if this node belongs to class metaspace.
+ bool is_class() const { return _is_class; }
+
+ // Helper function for take_from_committed: allocate padding chunks
+ // until top is at the given address.
+ void allocate_padding_chunks_until_top_is_at(MetaWord* target_top);
+
public:
- VirtualSpaceNode(size_t byte_size);
- VirtualSpaceNode(ReservedSpace rs) : _top(NULL), _next(NULL), _rs(rs), _container_count(0) {}
+ VirtualSpaceNode(bool is_class, size_t byte_size);
+ VirtualSpaceNode(bool is_class, ReservedSpace rs) :
+ _is_class(is_class), _top(NULL), _next(NULL), _rs(rs), _container_count(0), _occupancy_map(NULL) {}
~VirtualSpaceNode();
// Convenience functions for logical bottom and end
MetaWord* bottom() const { return (MetaWord*) _virtual_space.low(); }
MetaWord* end() const { return (MetaWord*) _virtual_space.high(); }
+ const OccupancyMap* occupancy_map() const { return _occupancy_map; }
+ OccupancyMap* occupancy_map() { return _occupancy_map; }
+
bool contains(const void* ptr) { return ptr >= low() && ptr < high(); }
size_t reserved_words() const { return _virtual_space.reserved_size() / BytesPerWord; }
@@ -424,12 +797,18 @@ class VirtualSpaceNode : public CHeapObj<mtClass> {
// the smallest chunk size.
void retire(ChunkManager* chunk_manager);
-#ifdef ASSERT
- // Debug support
- void mangle();
-#endif
void print_on(outputStream* st) const;
+ void print_map(outputStream* st, bool is_class) const;
+
+ // Debug support
+ DEBUG_ONLY(void mangle();)
+ // Verify counters, all chunks in this list node and the occupancy map.
+ DEBUG_ONLY(void verify();)
+ // Verify that all free chunks in this node are ideally merged
+ // (there not should be multiple small chunks where a large chunk could exist.)
+ DEBUG_ONLY(void verify_free_chunks_are_ideally_merged();)
+
};
#define assert_is_ptr_aligned(ptr, alignment) \
@@ -458,7 +837,8 @@ static bool should_commit_large_pages_when_reserving(size_t bytes) {
}
// byte_size is the size of the associated virtualspace.
-VirtualSpaceNode::VirtualSpaceNode(size_t bytes) : _top(NULL), _next(NULL), _rs(), _container_count(0) {
+VirtualSpaceNode::VirtualSpaceNode(bool is_class, size_t bytes) :
+ _is_class(is_class), _top(NULL), _next(NULL), _rs(), _container_count(0), _occupancy_map(NULL) {
assert_is_size_aligned(bytes, Metaspace::reserve_alignment());
#if INCLUDE_CDS
@@ -504,12 +884,14 @@ VirtualSpaceNode::VirtualSpaceNode(size_t bytes) : _top(NULL), _next(NULL), _rs(
}
void VirtualSpaceNode::purge(ChunkManager* chunk_manager) {
+ DEBUG_ONLY(this->verify();)
Metachunk* chunk = first_chunk();
Metachunk* invalid_chunk = (Metachunk*) top();
while (chunk < invalid_chunk ) {
assert(chunk->is_tagged_free(), "Should be tagged free");
MetaWord* next = ((MetaWord*)chunk) + chunk->word_size();
chunk_manager->remove_chunk(chunk);
+ chunk->remove_sentinel();
assert(chunk->next() == NULL &&
chunk->prev() == NULL,
"Was not removed from its list");
@@ -517,6 +899,88 @@ void VirtualSpaceNode::purge(ChunkManager* chunk_manager) {
}
}
+void VirtualSpaceNode::print_map(outputStream* st, bool is_class) const {
+
+ if (bottom() == top()) {
+ return;
+ }
+
+ const size_t spec_chunk_size = is_class ? ClassSpecializedChunk : SpecializedChunk;
+ const size_t small_chunk_size = is_class ? ClassSmallChunk : SmallChunk;
+ const size_t med_chunk_size = is_class ? ClassMediumChunk : MediumChunk;
+
+ int line_len = 100;
+ const size_t section_len = align_up(spec_chunk_size * line_len, med_chunk_size);
+ line_len = (int)(section_len / spec_chunk_size);
+
+ static const int NUM_LINES = 4;
+
+ char* lines[NUM_LINES];
+ for (int i = 0; i < NUM_LINES; i ++) {
+ lines[i] = (char*)os::malloc(line_len, mtInternal);
+ }
+ int pos = 0;
+ const MetaWord* p = bottom();
+ const Metachunk* chunk = (const Metachunk*)p;
+ const MetaWord* chunk_end = p + chunk->word_size();
+ while (p < top()) {
+ if (pos == line_len) {
+ pos = 0;
+ for (int i = 0; i < NUM_LINES; i ++) {
+ st->fill_to(22);
+ st->print_raw(lines[i], line_len);
+ st->cr();
+ }
+ }
+ if (pos == 0) {
+ st->print(PTR_FORMAT ":", p2i(p));
+ }
+ if (p == chunk_end) {
+ chunk = (Metachunk*)p;
+ chunk_end = p + chunk->word_size();
+ }
+ // line 1: chunk starting points (a dot if that area is a chunk start).
+ lines[0][pos] = p == (const MetaWord*)chunk ? '.' : ' ';
+
+ // Line 2: chunk type (x=spec, s=small, m=medium, h=humongous), uppercase if
+ // chunk is in use.
+ const bool chunk_is_free = ((Metachunk*)chunk)->is_tagged_free();
+ if (chunk->word_size() == spec_chunk_size) {
+ lines[1][pos] = chunk_is_free ? 'x' : 'X';
+ } else if (chunk->word_size() == small_chunk_size) {
+ lines[1][pos] = chunk_is_free ? 's' : 'S';
+ } else if (chunk->word_size() == med_chunk_size) {
+ lines[1][pos] = chunk_is_free ? 'm' : 'M';
+ } else if (chunk->word_size() > med_chunk_size) {
+ lines[1][pos] = chunk_is_free ? 'h' : 'H';
+ } else {
+ ShouldNotReachHere();
+ }
+
+ // Line 3: chunk origin
+ const ChunkOrigin origin = chunk->get_origin();
+ lines[2][pos] = origin == origin_normal ? ' ' : '0' + (int) origin;
+
+ // Line 4: Virgin chunk? Virgin chunks are chunks created as a byproduct of padding or splitting,
+ // but were never used.
+ lines[3][pos] = chunk->get_use_count() > 0 ? ' ' : 'v';
+
+ p += spec_chunk_size;
+ pos ++;
+ }
+ if (pos > 0) {
+ for (int i = 0; i < NUM_LINES; i ++) {
+ st->fill_to(22);
+ st->print_raw(lines[i], line_len);
+ st->cr();
+ }
+ }
+ for (int i = 0; i < NUM_LINES; i ++) {
+ os::free(lines[i]);
+ }
+}
+
+
#ifdef ASSERT
uint VirtualSpaceNode::container_count_slow() {
uint count = 0;
@@ -524,6 +988,7 @@ uint VirtualSpaceNode::container_count_slow() {
Metachunk* invalid_chunk = (Metachunk*) top();
while (chunk < invalid_chunk ) {
MetaWord* next = ((MetaWord*)chunk) + chunk->word_size();
+ do_verify_chunk(chunk);
// Don't count the chunks on the free lists. Those are
// still part of the VirtualSpaceNode but not currently
// counted.
@@ -536,6 +1001,77 @@ uint VirtualSpaceNode::container_count_slow() {
}
#endif
+#ifdef ASSERT
+// Verify counters, all chunks in this list node and the occupancy map.
+void VirtualSpaceNode::verify() {
+ uintx num_in_use_chunks = 0;
+ Metachunk* chunk = first_chunk();
+ Metachunk* invalid_chunk = (Metachunk*) top();
+
+ // Iterate the chunks in this node and verify each chunk.
+ while (chunk < invalid_chunk ) {
+ DEBUG_ONLY(do_verify_chunk(chunk);)
+ if (!chunk->is_tagged_free()) {
+ num_in_use_chunks ++;
+ }
+ MetaWord* next = ((MetaWord*)chunk) + chunk->word_size();
+ chunk = (Metachunk*) next;
+ }
+ assert(_container_count == num_in_use_chunks, err_msg("Container count mismatch (real: " UINTX_FORMAT
+ ", counter: " UINTX_FORMAT ".", num_in_use_chunks, _container_count));
+ // Also verify the occupancy map.
+ occupancy_map()->verify(this->bottom(), this->top());
+}
+#endif // ASSERT
+
+#ifdef ASSERT
+// Verify that all free chunks in this node are ideally merged
+// (there not should be multiple small chunks where a large chunk could exist.)
+void VirtualSpaceNode::verify_free_chunks_are_ideally_merged() {
+ Metachunk* chunk = first_chunk();
+ Metachunk* invalid_chunk = (Metachunk*) top();
+ // Shorthands.
+ const size_t size_med = (is_class() ? ClassMediumChunk : MediumChunk) * BytesPerWord;
+ const size_t size_small = (is_class() ? ClassSmallChunk : SmallChunk) * BytesPerWord;
+ int num_free_chunks_since_last_med_boundary = -1;
+ int num_free_chunks_since_last_small_boundary = -1;
+ while (chunk < invalid_chunk ) {
+ // Test for missed chunk merge opportunities: count number of free chunks since last chunk boundary.
+ // Reset the counter when encountering a non-free chunk.
+ if (chunk->get_chunk_type() != HumongousIndex) {
+ if (chunk->is_tagged_free()) {
+ // Count successive free, non-humongous chunks.
+ if (is_aligned(chunk, size_small)) {
+ assert(num_free_chunks_since_last_small_boundary <= 1,
+ err_msg("Missed chunk merge opportunity at " PTR_FORMAT " for chunk size " SIZE_FORMAT_HEX ".", p2i(chunk) - size_small, size_small));
+ num_free_chunks_since_last_small_boundary = 0;
+ } else if (num_free_chunks_since_last_small_boundary != -1) {
+ num_free_chunks_since_last_small_boundary ++;
+ }
+ if (is_aligned(chunk, size_med)) {
+ assert(num_free_chunks_since_last_med_boundary <= 1,
+ err_msg("Missed chunk merge opportunity at " PTR_FORMAT " for chunk size " SIZE_FORMAT_HEX ".", p2i(chunk) - size_med, size_med));
+ num_free_chunks_since_last_med_boundary = 0;
+ } else if (num_free_chunks_since_last_med_boundary != -1) {
+ num_free_chunks_since_last_med_boundary ++;
+ }
+ } else {
+ // Encountering a non-free chunk, reset counters.
+ num_free_chunks_since_last_med_boundary = -1;
+ num_free_chunks_since_last_small_boundary = -1;
+ }
+ } else {
+ // One cannot merge areas with a humongous chunk in the middle. Reset counters.
+ num_free_chunks_since_last_med_boundary = -1;
+ num_free_chunks_since_last_small_boundary = -1;
+ }
+
+ MetaWord* next = ((MetaWord*)chunk) + chunk->word_size();
+ chunk = (Metachunk*) next;
+ }
+}
+#endif // ASSERT
+
// List of VirtualSpaces for metadata allocation.
class VirtualSpaceList : public CHeapObj<mtClass> {
friend class VirtualSpaceNode;
@@ -623,6 +1159,7 @@ class VirtualSpaceList : public CHeapObj<mtClass> {
void purge(ChunkManager* chunk_manager);
void print_on(outputStream* st) const;
+ void print_map(outputStream* st) const;
class VirtualSpaceListIterator : public StackObj {
VirtualSpaceNode* _virtual_spaces;
@@ -728,8 +1265,6 @@ class SpaceManager : public CHeapObj<mtClass> {
Mutex* lock() const { return _lock; }
- const char* chunk_size_name(ChunkIndex index) const;
-
protected:
void initialize();
@@ -945,6 +1480,9 @@ void BlockFreelist::print_on(outputStream* st) const {
VirtualSpaceNode::~VirtualSpaceNode() {
_rs.release();
+ if (_occupancy_map != NULL) {
+ delete _occupancy_map;
+ }
#ifdef ASSERT
size_t word_size = sizeof(*this) / BytesPerWord;
Copy::fill_to_words((HeapWord*) this, word_size, 0xf1f1f1f1);
@@ -964,10 +1502,124 @@ size_t VirtualSpaceNode::free_words_in_vs() const {
return pointer_delta(end(), top(), sizeof(MetaWord));
}
+// Given an address larger than top(), allocate padding chunks until top is at the given address.
+void VirtualSpaceNode::allocate_padding_chunks_until_top_is_at(MetaWord* target_top) {
+
+ assert(target_top > top(), "Sanity");
+
+ // Padding chunks are added to the freelist.
+ ChunkManager* const chunk_manager = Metaspace::get_chunk_manager(this->is_class());
+
+ // shorthands
+ const size_t spec_word_size = chunk_manager->specialized_chunk_word_size();
+ const size_t small_word_size = chunk_manager->small_chunk_word_size();
+ const size_t med_word_size = chunk_manager->medium_chunk_word_size();
+
+ while (top() < target_top) {
+
+ // We could make this coding more generic, but right now we only deal with two possible chunk sizes
+ // for padding chunks, so it is not worth it.
+ size_t padding_chunk_word_size = small_word_size;
+ if (is_aligned(top(), small_word_size * sizeof(MetaWord)) == false) {
+ assert_is_ptr_aligned(top(), spec_word_size * sizeof(MetaWord)); // Should always hold true.
+ padding_chunk_word_size = spec_word_size;
+ }
+ MetaWord* here = top();
+ assert_is_ptr_aligned(here, padding_chunk_word_size * sizeof(MetaWord));
+ inc_top(padding_chunk_word_size);
+
+ // Create new padding chunk.
+ ChunkIndex padding_chunk_type = get_chunk_type_by_size(padding_chunk_word_size, is_class());
+ assert(padding_chunk_type == SpecializedIndex || padding_chunk_type == SmallIndex, "sanity");
+
+ Metachunk* const padding_chunk =
+ ::new (here) Metachunk(padding_chunk_type, is_class(), padding_chunk_word_size, this);
+ assert(padding_chunk == (Metachunk*)here, "Sanity");
+ DEBUG_ONLY(padding_chunk->set_origin(origin_pad);)
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Created padding chunk in %s at "
+ PTR_FORMAT ", size " SIZE_FORMAT_HEX ".",
+ (is_class() ? "class space " : "metaspace"),
+ p2i(padding_chunk), padding_chunk->word_size() * sizeof(MetaWord));
+ }
+
+ // Mark chunk start in occupancy map.
+ occupancy_map()->set_chunk_starts_at_address((MetaWord*)padding_chunk, true);
+
+ // Chunks are born as in-use (see MetaChunk ctor). So, before returning
+ // the padding chunk to its chunk manager, mark it as in use (ChunkManager
+ // will assert that).
+ do_update_in_use_info_for_chunk(padding_chunk, true);
+
+ // Return Chunk to freelist.
+ inc_container_count();
+ chunk_manager->return_single_chunk(padding_chunk_type, padding_chunk);
+ // Please note: at this point, ChunkManager::return_single_chunk()
+ // may already have merged the padding chunk with neighboring chunks, so
+ // it may have vanished at this point. Do not reference the padding
+ // chunk beyond this point.
+ }
+
+ assert(top() == target_top, "Sanity");
+
+} // allocate_padding_chunks_until_top_is_at()
+
// Allocates the chunk from the virtual space only.
// This interface is also used internally for debugging. Not all
// chunks removed here are necessarily used for allocation.
Metachunk* VirtualSpaceNode::take_from_committed(size_t chunk_word_size) {
+ // Non-humongous chunks are to be allocated aligned to their chunk
+ // size. So, start addresses of medium chunks are aligned to medium
+ // chunk size, those of small chunks to small chunk size and so
+ // forth. This facilitates merging of free chunks and reduces
+ // fragmentation. Chunk sizes are spec < small < medium, with each
+ // larger chunk size being a multiple of the next smaller chunk
+ // size.
+ // Because of this alignment, me may need to create a number of padding
+ // chunks. These chunks are created and added to the freelist.
+
+ // The chunk manager to which we will give our padding chunks.
+ ChunkManager* const chunk_manager = Metaspace::get_chunk_manager(this->is_class());
+
+ // shorthands
+ const size_t spec_word_size = chunk_manager->specialized_chunk_word_size();
+ const size_t small_word_size = chunk_manager->small_chunk_word_size();
+ const size_t med_word_size = chunk_manager->medium_chunk_word_size();
+
+ assert(chunk_word_size == spec_word_size || chunk_word_size == small_word_size ||
+ chunk_word_size >= med_word_size, "Invalid chunk size requested.");
+
+ // Chunk alignment (in bytes) == chunk size unless humongous.
+ // Humongous chunks are aligned to the smallest chunk size (spec).
+ const size_t required_chunk_alignment = (chunk_word_size > med_word_size ?
+ spec_word_size : chunk_word_size) * sizeof(MetaWord);
+
+ // Do we have enough space to create the requested chunk plus
+ // any padding chunks needed?
+ MetaWord* const next_aligned =
+ static_cast<MetaWord*>(align_up(top(), required_chunk_alignment));
+ if (!is_available((next_aligned - top()) + chunk_word_size)) {
+ return NULL;
+ }
+
+ // Before allocating the requested chunk, allocate padding chunks if necessary.
+ // We only need to do this for small or medium chunks: specialized chunks are the
+ // smallest size, hence always aligned. Homungous chunks are allocated unaligned
+ // (implicitly, also aligned to smallest chunk size).
+ if ((chunk_word_size == med_word_size || chunk_word_size == small_word_size) && next_aligned > top()) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Creating padding chunks in %s between %p and %p...",
+ (is_class() ? "class space " : "metaspace"),
+ top(), next_aligned);
+ }
+ allocate_padding_chunks_until_top_is_at(next_aligned);
+ // Now, top should be aligned correctly.
+ assert_is_ptr_aligned(top(), required_chunk_alignment);
+ }
+
+ // Now, top should be aligned correctly.
+ assert_is_ptr_aligned(top(), required_chunk_alignment);
+
// Bottom of the new chunk
MetaWord* chunk_limit = top();
assert(chunk_limit != NULL, "Not safe to call this method");
@@ -991,7 +1643,20 @@ Metachunk* VirtualSpaceNode::take_from_committed(size_t chunk_word_size) {
inc_top(chunk_word_size);
// Initialize the chunk
- Metachunk* result = ::new (chunk_limit) Metachunk(chunk_word_size, this);
+ ChunkIndex chunk_type = get_chunk_type_by_size(chunk_word_size, is_class());
+ Metachunk* result = ::new (chunk_limit) Metachunk(chunk_type, is_class(), chunk_word_size, this);
+ assert(result == (Metachunk*)chunk_limit, "Sanity");
+ occupancy_map()->set_chunk_starts_at_address((MetaWord*)result, true);
+ do_update_in_use_info_for_chunk(result, true);
+
+ inc_container_count();
+
+ DEBUG_ONLY(chunk_manager->locked_verify());
+ DEBUG_ONLY(this->verify());
+ DEBUG_ONLY(do_verify_chunk(result));
+
+ result->inc_use_count();
+
return result;
}
@@ -1010,6 +1675,16 @@ bool VirtualSpaceNode::expand_by(size_t min_words, size_t preferred_words) {
size_t commit = MIN2(preferred_bytes, uncommitted);
bool result = virtual_space()->expand_by(commit, false);
+ if (TraceMetadataChunkAllocation) {
+ if (result) {
+ gclog_or_tty->print_cr("Expanded %s virtual space list node by " SIZE_FORMAT " words.",
+ (is_class() ? "class" : "non-class"), commit);
+ } else {
+ gclog_or_tty->print_cr("Failed to expand %s virtual space list node by " SIZE_FORMAT " words.",
+ (is_class() ? "class" : "non-class"), commit);
+ }
+ }
+
assert(result, "Failed to commit memory");
return result;
@@ -1018,9 +1693,6 @@ bool VirtualSpaceNode::expand_by(size_t min_words, size_t preferred_words) {
Metachunk* VirtualSpaceNode::get_chunk_vs(size_t chunk_word_size) {
assert_lock_strong(SpaceManager::expand_lock());
Metachunk* result = take_from_committed(chunk_word_size);
- if (result != NULL) {
- inc_container_count();
- }
return result;
}
@@ -1060,6 +1732,10 @@ bool VirtualSpaceNode::initialize() {
_rs.size() / BytesPerWord));
}
+ // Initialize Occupancy Map.
+ const size_t smallest_chunk_size = is_class() ? ClassSpecializedChunk : SpecializedChunk;
+ _occupancy_map = new OccupancyMap(bottom(), reserved_words(), smallest_chunk_size);
+
return result;
}
@@ -1140,8 +1816,140 @@ void ChunkManager::remove_chunk(Metachunk* chunk) {
humongous_dictionary()->remove_chunk(chunk);
}
- // Chunk is being removed from the chunks free list.
- dec_free_chunks_total(chunk->word_size());
+ // Chunk has been removed from the chunks free list, update counters.
+ account_for_removed_chunk(chunk);
+}
+
+bool ChunkManager::attempt_to_coalesce_around_chunk(Metachunk* chunk, ChunkIndex target_chunk_type) {
+ assert_lock_strong(SpaceManager::expand_lock());
+ assert(chunk != NULL, "invalid chunk pointer");
+ // Check for valid merge combinations.
+ assert((chunk->get_chunk_type() == SpecializedIndex &&
+ (target_chunk_type == SmallIndex || target_chunk_type == MediumIndex)) ||
+ (chunk->get_chunk_type() == SmallIndex && target_chunk_type == MediumIndex),
+ "Invalid chunk merge combination.");
+
+ const size_t target_chunk_word_size =
+ get_size_for_nonhumongous_chunktype(target_chunk_type, this->is_class());
+
+ // [ prospective merge region )
+ MetaWord* const p_merge_region_start =
+ (MetaWord*) align_down(chunk, target_chunk_word_size * sizeof(MetaWord));
+ MetaWord* const p_merge_region_end =
+ p_merge_region_start + target_chunk_word_size;
+
+ // We need the VirtualSpaceNode containing this chunk and its occupancy map.
+ VirtualSpaceNode* const vsn = chunk->container();
+ OccupancyMap* const ocmap = vsn->occupancy_map();
+
+ // The prospective chunk merge range must be completely contained by the
+ // committed range of the virtual space node.
+ if (p_merge_region_start < vsn->bottom() || p_merge_region_end > vsn->top()) {
+ return false;
+ }
+
+ // Only attempt to merge this range if at its start a chunk starts and at its end
+ // a chunk ends. If a chunk (can only be humongous) straddles either start or end
+ // of that range, we cannot merge.
+ if (!ocmap->chunk_starts_at_address(p_merge_region_start)) {
+ return false;
+ }
+ if (p_merge_region_end < vsn->top() &&
+ !ocmap->chunk_starts_at_address(p_merge_region_end)) {
+ return false;
+ }
+
+ // Now check if the prospective merge area contains live chunks. If it does we cannot merge.
+ if (ocmap->is_region_in_use(p_merge_region_start, target_chunk_word_size)) {
+ return false;
+ }
+
+ // Success! Remove all chunks in this region...
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("%s: coalescing chunks in area [%p-%p)...",
+ (is_class() ? "class space" : "metaspace"),
+ p_merge_region_start, p_merge_region_end);
+ }
+
+ const int num_chunks_removed =
+ remove_chunks_in_area(p_merge_region_start, target_chunk_word_size);
+
+ // ... and create a single new bigger chunk.
+ Metachunk* const p_new_chunk =
+ ::new (p_merge_region_start) Metachunk(target_chunk_type, is_class(), target_chunk_word_size, vsn);
+ assert(p_new_chunk == (Metachunk*)p_merge_region_start, "Sanity");
+ p_new_chunk->set_origin(origin_merge);
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("%s: created coalesced chunk at %p, size " SIZE_FORMAT_HEX ".",
+ (is_class() ? "class space" : "metaspace"),
+ p_new_chunk, p_new_chunk->word_size() * sizeof(MetaWord));
+ }
+
+ // Fix occupancy map: remove old start bits of the small chunks and set new start bit.
+ ocmap->wipe_chunk_start_bits_in_region(p_merge_region_start, target_chunk_word_size);
+ ocmap->set_chunk_starts_at_address(p_merge_region_start, true);
+
+ // Mark chunk as free. Note: it is not necessary to update the occupancy
+ // map in-use map, because the old chunks were also free, so nothing
+ // should have changed.
+ p_new_chunk->set_is_tagged_free(true);
+
+ // Add new chunk to its freelist.
+ ChunkList* const list = free_chunks(target_chunk_type);
+ list->return_chunk_at_head(p_new_chunk);
+
+ // And adjust ChunkManager:: _free_chunks_count (_free_chunks_total
+ // should not have changed, because the size of the space should be the same)
+ _free_chunks_count -= num_chunks_removed;
+ _free_chunks_count ++;
+
+ // VirtualSpaceNode::container_count does not have to be modified:
+ // it means "number of active (non-free) chunks", so merging free chunks
+ // should not affect that count.
+
+ // At the end of a chunk merge, run verification tests.
+ DEBUG_ONLY(this->locked_verify());
+ DEBUG_ONLY(vsn->verify());
+
+ return true;
+}
+
+// Remove all chunks in the given area - the chunks are supposed to be free -
+// from their corresponding freelists. Mark them as invalid.
+// - This does not correct the occupancy map.
+// - This does not adjust the counters in ChunkManager.
+// - Does not adjust container count counter in containing VirtualSpaceNode
+// Returns number of chunks removed.
+int ChunkManager::remove_chunks_in_area(MetaWord* p, size_t word_size) {
+ assert(p != NULL && word_size > 0, "Invalid range.");
+ const size_t smallest_chunk_size = get_size_for_nonhumongous_chunktype(SpecializedIndex, is_class());
+ assert_is_size_aligned(word_size, smallest_chunk_size);
+
+ Metachunk* const start = (Metachunk*) p;
+ const Metachunk* const end = (Metachunk*)(p + word_size);
+ Metachunk* cur = start;
+ int num_removed = 0;
+ while (cur < end) {
+ Metachunk* next = (Metachunk*)(((MetaWord*)cur) + cur->word_size());
+ DEBUG_ONLY(do_verify_chunk(cur));
+ assert(cur->get_chunk_type() != HumongousIndex, err_msg("Unexpected humongous chunk found at %p.", cur));
+ assert(cur->is_tagged_free(), err_msg("Chunk expected to be free (%p)", cur));
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("%s: removing chunk %p, size " SIZE_FORMAT_HEX ".",
+ (is_class() ? "class space" : "metaspace"),
+ cur, cur->word_size() * sizeof(MetaWord));
+ }
+ cur->remove_sentinel();
+ // Note: cannot call ChunkManager::remove_chunk, because that
+ // modifies the counters in ChunkManager, which we do not want. So
+ // we call remove_chunk on the freelist directly (see also the
+ // splitting function which does the same).
+ ChunkList* const list = free_chunks(list_index(cur->word_size()));
+ list->remove_chunk(cur);
+ num_removed ++;
+ cur = next;
+ }
+ return num_removed;
}
// Walk the list of VirtualSpaceNodes and delete
@@ -1161,6 +1969,10 @@ void VirtualSpaceList::purge(ChunkManager* chunk_manager) {
// Don't free the current virtual space since it will likely
// be needed soon.
if (vsl->container_count() == 0 && vsl != current_virtual_space()) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Purging VirtualSpaceNode " PTR_FORMAT " (capacity: " SIZE_FORMAT
+ ", used: " SIZE_FORMAT ").", p2i(vsl), vsl->capacity_words_in_vs(), vsl->used_words_in_vs());
+ }
// Unlink it from the list
if (prev_vsl == vsl) {
// This is the case of the current node being the first node.
@@ -1221,17 +2033,24 @@ void VirtualSpaceList::retire_current_virtual_space() {
}
void VirtualSpaceNode::retire(ChunkManager* chunk_manager) {
+ assert(this->is_class() == chunk_manager->is_class(), "Wrong ChunkManager?");
for (int i = (int)MediumIndex; i >= (int)ZeroIndex; --i) {
ChunkIndex index = (ChunkIndex)i;
- size_t chunk_size = chunk_manager->free_chunks(index)->size();
+ size_t chunk_size = chunk_manager->size_by_index(index);
while (free_words_in_vs() >= chunk_size) {
DEBUG_ONLY(verify_container_count();)
Metachunk* chunk = get_chunk_vs(chunk_size);
- assert(chunk != NULL, "allocation should have been successful");
-
- chunk_manager->return_chunks(index, chunk);
- chunk_manager->inc_free_chunks_total(chunk_size);
+ // Chunk will be allocated aligned, so allocation may require
+ // additional padding chunks. That may cause above allocation to
+ // fail. Just ignore the failed allocation and continue with the
+ // next smaller chunk size. As the VirtualSpaceNode comitted
+ // size should be a multiple of the smallest chunk size, we
+ // should always be able to fill the VirtualSpace completely.
+ if (chunk == NULL) {
+ break;
+ }
+ chunk_manager->return_single_chunk(index, chunk);
DEBUG_ONLY(verify_container_count();)
}
}
@@ -1259,7 +2078,7 @@ VirtualSpaceList::VirtualSpaceList(ReservedSpace rs) :
_virtual_space_count(0) {
MutexLockerEx cl(SpaceManager::expand_lock(),
Mutex::_no_safepoint_check_flag);
- VirtualSpaceNode* class_entry = new VirtualSpaceNode(rs);
+ VirtualSpaceNode* class_entry = new VirtualSpaceNode(is_class(), rs);
bool succeeded = class_entry->initialize();
if (succeeded) {
link_vs(class_entry);
@@ -1291,7 +2110,7 @@ bool VirtualSpaceList::create_new_virtual_space(size_t vs_word_size) {
assert_is_size_aligned(vs_byte_size, Metaspace::reserve_alignment());
// Allocate the meta virtual space and initialize it.
- VirtualSpaceNode* new_entry = new VirtualSpaceNode(vs_byte_size);
+ VirtualSpaceNode* new_entry = new VirtualSpaceNode(is_class(), vs_byte_size);
if (!new_entry->initialize()) {
delete new_entry;
return false;
@@ -1345,12 +2164,22 @@ bool VirtualSpaceList::expand_by(size_t min_words, size_t preferred_words) {
assert_is_size_aligned(preferred_words, Metaspace::commit_alignment_words());
assert(min_words <= preferred_words, "Invalid arguments");
+ const char* const class_or_not = (is_class() ? "class" : "non-class");
+
if (!MetaspaceGC::can_expand(min_words, this->is_class())) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Cannot expand %s virtual space list.",
+ class_or_not);
+ }
return false;
}
size_t allowed_expansion_words = MetaspaceGC::allowed_expansion();
if (allowed_expansion_words < min_words) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Cannot expand %s virtual space list (must try gc first).",
+ class_or_not);
+ }
return false;
}
@@ -1361,8 +2190,16 @@ bool VirtualSpaceList::expand_by(size_t min_words, size_t preferred_words) {
min_words,
max_expansion_words);
if (vs_expanded) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Expanded %s virtual space list.",
+ class_or_not);
+ }
return true;
}
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("%s virtual space list: retire current node.",
+ class_or_not);
+ }
retire_current_virtual_space();
// Get another virtual space.
@@ -1386,6 +2223,24 @@ bool VirtualSpaceList::expand_by(size_t min_words, size_t preferred_words) {
return false;
}
+// Given a chunk, calculate the largest possible padding space which
+// could be required when allocating it.
+static size_t largest_possible_padding_size_for_chunk(size_t chunk_word_size, bool is_class) {
+ const ChunkIndex chunk_type = get_chunk_type_by_size(chunk_word_size, is_class);
+ if (chunk_type != HumongousIndex) {
+ // Normal, non-humongous chunks are allocated at chunk size
+ // boundaries, so the largest padding space required would be that
+ // minus the smallest chunk size.
+ const size_t smallest_chunk_size = is_class ? ClassSpecializedChunk : SpecializedChunk;
+ return chunk_word_size - smallest_chunk_size;
+ } else {
+ // Humongous chunks are allocated at smallest-chunksize
+ // boundaries, so there is no padding required.
+ return 0;
+ }
+}
+
+
Metachunk* VirtualSpaceList::get_new_chunk(size_t chunk_word_size, size_t suggested_commit_granularity) {
// Allocate a chunk out of the current virtual space.
@@ -1398,7 +2253,11 @@ Metachunk* VirtualSpaceList::get_new_chunk(size_t chunk_word_size, size_t sugges
// The expand amount is currently only determined by the requested sizes
// and not how much committed memory is left in the current virtual space.
- size_t min_word_size = align_size_up(chunk_word_size, Metaspace::commit_alignment_words());
+ // We must have enough space for the requested size and any
+ // additional reqired padding chunks.
+ const size_t size_for_padding = largest_possible_padding_size_for_chunk(chunk_word_size, this->is_class());
+
+ size_t min_word_size = align_size_up(chunk_word_size + size_for_padding, Metaspace::commit_alignment_words());
size_t preferred_word_size = align_size_up(suggested_commit_granularity, Metaspace::commit_alignment_words());
if (min_word_size >= preferred_word_size) {
// Can happen when humongous chunks are allocated.
@@ -1424,6 +2283,18 @@ void VirtualSpaceList::print_on(outputStream* st) const {
}
}
+void VirtualSpaceList::print_map(outputStream* st) const {
+ VirtualSpaceNode* list = virtual_space_list();
+ VirtualSpaceListIterator iter(list);
+ unsigned i = 0;
+ while (iter.repeat()) {
+ st->print_cr("Node %u:", i);
+ VirtualSpaceNode* node = iter.get_next();
+ node->print_map(st, this->is_class());
+ i ++;
+ }
+}
+
// MetaspaceGC methods
// VM_CollectForMetadataAllocation is the vm operation used to GC.
@@ -1547,6 +2418,10 @@ bool MetaspaceGC::can_expand(size_t word_size, bool is_class) {
if (is_class && Metaspace::using_class_space()) {
size_t class_committed = MetaspaceAux::committed_bytes(Metaspace::ClassType);
if (class_committed + word_size * BytesPerWord > CompressedClassSpaceSize) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Cannot expand %s metaspace by " SIZE_FORMAT " words (CompressedClassSpaceSize = " SIZE_FORMAT " words)",
+ (is_class ? "class" : "non-class"), word_size, CompressedClassSpaceSize / sizeof(MetaWord));
+ }
return false;
}
}
@@ -1554,6 +2429,10 @@ bool MetaspaceGC::can_expand(size_t word_size, bool is_class) {
// Check if the user has imposed a limit on the metaspace memory.
size_t committed_bytes = MetaspaceAux::committed_bytes();
if (committed_bytes + word_size * BytesPerWord > MaxMetaspaceSize) {
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Cannot expand %s metaspace by " SIZE_FORMAT " words (MaxMetaspaceSize = " SIZE_FORMAT " words)",
+ (is_class ? "class" : "non-class"), word_size, MaxMetaspaceSize / sizeof(MetaWord));
+ }
return false;
}
@@ -1571,6 +2450,11 @@ size_t MetaspaceGC::allowed_expansion() {
size_t left_until_max = MaxMetaspaceSize - committed_bytes;
size_t left_until_GC = capacity_until_gc - committed_bytes;
size_t left_to_commit = MIN2(left_until_GC, left_until_max);
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("allowed expansion words: " SIZE_FORMAT
+ " (left_until_max: " SIZE_FORMAT ", left_until_GC: " SIZE_FORMAT ".",
+ left_to_commit / BytesPerWord, left_until_max / BytesPerWord, left_until_GC / BytesPerWord);
+ }
return left_to_commit / BytesPerWord;
}
@@ -1762,6 +2646,25 @@ size_t ChunkManager::free_chunks_total_bytes() {
return free_chunks_total_words() * BytesPerWord;
}
+// Update internal accounting after a chunk was added
+void ChunkManager::account_for_added_chunk(const Metachunk* c) {
+ assert_lock_strong(SpaceManager::expand_lock());
+ _free_chunks_count ++;
+ _free_chunks_total += c->word_size();
+}
+
+// Update internal accounting after a chunk was removed
+void ChunkManager::account_for_removed_chunk(const Metachunk* c) {
+ assert_lock_strong(SpaceManager::expand_lock());
+ assert(_free_chunks_count >= 1,
+ err_msg("ChunkManager::_free_chunks_count: about to go negative (" SIZE_FORMAT ").", _free_chunks_count));
+ assert(_free_chunks_total >= c->word_size(),
+ err_msg("ChunkManager::_free_chunks_total: about to go negative"
+ "(now: " SIZE_FORMAT ", decrement value: " SIZE_FORMAT ").", _free_chunks_total, c->word_size()));
+ _free_chunks_count --;
+ _free_chunks_total -= c->word_size();
+}
+
size_t ChunkManager::free_chunks_count() {
#ifdef ASSERT
if (!UseConcMarkSweepGC && !SpaceManager::expand_lock()->is_locked()) {
@@ -1775,6 +2678,22 @@ size_t ChunkManager::free_chunks_count() {
return _free_chunks_count;
}
+ChunkIndex ChunkManager::list_index(size_t size) {
+ if (size_by_index(SpecializedIndex) == size) {
+ return SpecializedIndex;
+ }
+ if (size_by_index(SmallIndex) == size) {
+ return SmallIndex;
+ }
+ const size_t med_size = size_by_index(MediumIndex);
+ if (med_size == size) {
+ return MediumIndex;
+ }
+
+ assert(size > med_size, "Not a humongous chunk");
+ return HumongousIndex;
+}
+
size_t ChunkManager::size_by_index(ChunkIndex index) const {
index_bounds_check(index);
assert(index != HumongousIndex, "Do not call for humongous chunks.");
@@ -1820,6 +2739,17 @@ void ChunkManager::verify() {
void ChunkManager::locked_verify() {
locked_verify_free_chunks_count();
locked_verify_free_chunks_total();
+ for (ChunkIndex i = ZeroIndex; i < NumberOfFreeLists; i = next_chunk_index(i)) {
+ ChunkList* list = free_chunks(i);
+ if (list != NULL) {
+ Metachunk* chunk = list->head();
+ while (chunk) {
+ DEBUG_ONLY(do_verify_chunk(chunk);)
+ assert(chunk->is_tagged_free(), "Chunk should be tagged as free.");
+ chunk = chunk->next();
+ }
+ }
+ }
}
void ChunkManager::locked_print_free_chunks(outputStream* st) {
@@ -1879,18 +2809,166 @@ ChunkList* ChunkManager::find_free_chunks_list(size_t word_size) {
return free_chunks(index);
}
+// Helper for chunk splitting: given a target chunk size and a larger free chunk,
+// split up the larger chunk into n smaller chunks, at least one of which should be
+// the target chunk of target chunk size. The smaller chunks, including the target
+// chunk, are returned to the freelist. The pointer to the target chunk is returned.
+// Note that this chunk is supposed to be removed from the freelist right away.
+Metachunk* ChunkManager::split_chunk(size_t target_chunk_word_size, Metachunk* larger_chunk) {
+ assert(larger_chunk->word_size() > target_chunk_word_size, "Sanity");
+
+ const ChunkIndex larger_chunk_index = larger_chunk->get_chunk_type();
+ const ChunkIndex target_chunk_index = get_chunk_type_by_size(target_chunk_word_size, is_class());
+
+ MetaWord* const region_start = (MetaWord*)larger_chunk;
+ const size_t region_word_len = larger_chunk->word_size();
+ MetaWord* const region_end = region_start + region_word_len;
+ VirtualSpaceNode* const vsn = larger_chunk->container();
+ OccupancyMap* const ocmap = vsn->occupancy_map();
+
+ // Any larger non-humongous chunk size is a multiple of any smaller chunk size.
+ // Since non-humongous chunks are aligned to their chunk size, the larger chunk should start
+ // at an address suitable to place the smaller target chunk.
+ assert_is_ptr_aligned(region_start, target_chunk_word_size);
+
+ // Remove old chunk.
+ free_chunks(larger_chunk_index)->remove_chunk(larger_chunk);
+ larger_chunk->remove_sentinel();
+
+ // Prevent access to the old chunk from here on.
+ larger_chunk = NULL;
+ // ... and wipe it.
+ DEBUG_ONLY(memset(region_start, 0xfe, region_word_len * BytesPerWord));
+
+ // In its place create first the target chunk...
+ MetaWord* p = region_start;
+ Metachunk* target_chunk = ::new (p) Metachunk(target_chunk_index, is_class(), target_chunk_word_size, vsn);
+ assert(target_chunk == (Metachunk*)p, "Sanity");
+ target_chunk->set_origin(origin_split);
+
+ // Note: we do not need to mark its start in the occupancy map
+ // because it coincides with the old chunk start.
+
+ // Mark chunk as free and return to the freelist.
+ do_update_in_use_info_for_chunk(target_chunk, false);
+ free_chunks(target_chunk_index)->return_chunk_at_head(target_chunk);
+
+ // This chunk should now be valid and can be verified.
+ DEBUG_ONLY(do_verify_chunk(target_chunk));
+
+ // In the remaining space create the remainder chunks.
+ p += target_chunk->word_size();
+ assert(p < region_end, "Sanity");
+
+ while (p < region_end) {
+
+ // Find the largest chunk size which fits the alignment requirements at address p.
+ ChunkIndex this_chunk_index = prev_chunk_index(larger_chunk_index);
+ size_t this_chunk_word_size = 0;
+ for(;;) {
+ this_chunk_word_size = get_size_for_nonhumongous_chunktype(this_chunk_index, is_class());
+ if (is_aligned(p, this_chunk_word_size * BytesPerWord)) {
+ break;
+ } else {
+ this_chunk_index = prev_chunk_index(this_chunk_index);
+ assert(this_chunk_index >= target_chunk_index, "Sanity");
+ }
+ }
+
+ assert(this_chunk_word_size >= target_chunk_word_size, "Sanity");
+ assert(is_aligned(p, this_chunk_word_size * BytesPerWord), "Sanity");
+ assert(p + this_chunk_word_size <= region_end, "Sanity");
+
+ // Create splitting chunk.
+ Metachunk* this_chunk = ::new (p) Metachunk(this_chunk_index, is_class(), this_chunk_word_size, vsn);
+ assert(this_chunk == (Metachunk*)p, "Sanity");
+ this_chunk->set_origin(origin_split);
+ ocmap->set_chunk_starts_at_address(p, true);
+ do_update_in_use_info_for_chunk(this_chunk, false);
+
+ // This chunk should be valid and can be verified.
+ DEBUG_ONLY(do_verify_chunk(this_chunk));
+
+ // Return this chunk to freelist and correct counter.
+ free_chunks(this_chunk_index)->return_chunk_at_head(this_chunk);
+ _free_chunks_count ++;
+
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("Created chunk at " PTR_FORMAT ", word size "
+ SIZE_FORMAT_HEX " (%s), in split region [" PTR_FORMAT "..." PTR_FORMAT ").",
+ p2i(this_chunk), this_chunk->word_size(), chunk_size_name(this_chunk_index),
+ p2i(region_start), p2i(region_end));
+ }
+
+ p += this_chunk_word_size;
+
+ }
+
+ return target_chunk;
+}
+
Metachunk* ChunkManager::free_chunks_get(size_t word_size) {
assert_lock_strong(SpaceManager::expand_lock());
slow_locked_verify();
Metachunk* chunk = NULL;
+ bool we_did_split_a_chunk = false;
+
if (list_index(word_size) != HumongousIndex) {
+
ChunkList* free_list = find_free_chunks_list(word_size);
assert(free_list != NULL, "Sanity check");
chunk = free_list->head();
+ if (chunk == NULL) {
+ // Split large chunks into smaller chunks if there are no smaller chunks, just large chunks.
+ // This is the counterpart of the coalescing-upon-chunk-return.
+
+ ChunkIndex target_chunk_index = get_chunk_type_by_size(word_size, is_class());
+
+ // Is there a larger chunk we could split?
+ Metachunk* larger_chunk = NULL;
+ ChunkIndex larger_chunk_index = next_chunk_index(target_chunk_index);
+ while (larger_chunk == NULL && larger_chunk_index < NumberOfFreeLists) {
+ larger_chunk = free_chunks(larger_chunk_index)->head();
+ if (larger_chunk == NULL) {
+ larger_chunk_index = next_chunk_index(larger_chunk_index);
+ }
+ }
+
+ if (larger_chunk != NULL) {
+ assert(larger_chunk->word_size() > word_size, "Sanity");
+ assert(larger_chunk->get_chunk_type() == larger_chunk_index, "Sanity");
+
+ // We found a larger chunk. Lets split it up:
+ // - remove old chunk
+ // - in its place, create new smaller chunks, with at least one chunk
+ // being of target size, the others sized as large as possible. This
+ // is to make sure the resulting chunks are "as coalesced as possible"
+ // (similar to VirtualSpaceNode::retire()).
+ // Note: during this operation both ChunkManager and VirtualSpaceNode
+ // are temporarily invalid, so be careful with asserts.
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("%s: splitting chunk " PTR_FORMAT
+ ", word size " SIZE_FORMAT_HEX " (%s), to get a chunk of word size " SIZE_FORMAT_HEX " (%s)...",
+ (is_class() ? "class space" : "metaspace"), p2i(larger_chunk), larger_chunk->word_size(),
+ chunk_size_name(larger_chunk_index), word_size, chunk_size_name(target_chunk_index));
+ }
+
+ chunk = split_chunk(word_size, larger_chunk);
+
+ // This should have worked.
+ assert(chunk != NULL, "Sanity");
+ assert(chunk->word_size() == word_size, "Sanity");
+ assert(chunk->is_tagged_free(), "Sanity");
+
+ we_did_split_a_chunk = true;
+
+ }
+ }
+
if (chunk == NULL) {
return NULL;
}
@@ -1899,9 +2977,8 @@ Metachunk* ChunkManager::free_chunks_get(size_t word_size) {
free_list->remove_chunk(chunk);
if (TraceMetadataChunkAllocation && Verbose) {
- gclog_or_tty->print_cr("ChunkManager::free_chunks_get: free_list "
- PTR_FORMAT " head " PTR_FORMAT " size " SIZE_FORMAT,
- free_list, chunk, chunk->word_size());
+ gclog_or_tty->print_cr("ChunkManager::free_chunks_get: free_list: " PTR_FORMAT " chunks left: " SSIZE_FORMAT ".",
+ p2i(free_list), free_list->count());
}
} else {
chunk = humongous_dictionary()->get_chunk(
@@ -1921,20 +2998,26 @@ Metachunk* ChunkManager::free_chunks_get(size_t word_size) {
}
}
- // Chunk is being removed from the chunks free list.
- dec_free_chunks_total(chunk->word_size());
+ // Chunk has been removed from the chunk manager; update counters.
+ account_for_removed_chunk(chunk);
+ do_update_in_use_info_for_chunk(chunk, true);
+ chunk->container()->inc_container_count();
+ chunk->inc_use_count();
// Remove it from the links to this freelist
chunk->set_next(NULL);
chunk->set_prev(NULL);
+
+ // Run some verifications (some more if we did a chunk split)
#ifdef ASSERT
- // Chunk is no longer on any freelist. Setting to false make container_count_slow()
- // work.
- chunk->set_is_tagged_free(false);
+ locked_verify();
+ VirtualSpaceNode* const vsn = chunk->container();
+ vsn->verify();
+ if (we_did_split_a_chunk) {
+ vsn->verify_free_chunks_are_ideally_merged();
+ }
#endif
- chunk->container()->inc_container_count();
- slow_locked_verify();
return chunk;
}
@@ -1968,6 +3051,97 @@ Metachunk* ChunkManager::chunk_freelist_allocate(size_t word_size) {
return chunk;
}
+void ChunkManager::return_single_chunk(ChunkIndex index, Metachunk* chunk) {
+ assert_lock_strong(SpaceManager::expand_lock());
+ DEBUG_ONLY(do_verify_chunk(chunk);)
+ assert(chunk->get_chunk_type() == index, "Chunk does not match expected index.");
+ assert(chunk != NULL, "Expected chunk.");
+ assert(chunk->container() != NULL, "Container should have been set.");
+ assert(chunk->is_tagged_free() == false, "Chunk should be in use.");
+ index_bounds_check(index);
+
+ // Note: mangle *before* returning the chunk to the freelist or dictionary. It does not
+ // matter for the freelist (non-humongous chunks), but the humongous chunk dictionary
+ // keeps tree node pointers in the chunk payload area which mangle will overwrite.
+ DEBUG_ONLY(chunk->mangle(badMetaWordVal);)
+
+ if (index != HumongousIndex) {
+ // Return non-humongous chunk to freelist.
+ ChunkList* list = free_chunks(index);
+ assert(list->size() == chunk->word_size(), "Wrong chunk type.");
+ list->return_chunk_at_head(chunk);
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("returned one %s chunk at " PTR_FORMAT " to freelist.",
+ chunk_size_name(index), p2i(chunk));
+ }
+ } else {
+ // Return humongous chunk to dictionary.
+ assert(chunk->word_size() > free_chunks(MediumIndex)->size(), "Wrong chunk type.");
+ assert(chunk->word_size() % free_chunks(SpecializedIndex)->size() == 0,
+ "Humongous chunk has wrong alignment.");
+ _humongous_dictionary.return_chunk(chunk);
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("returned one %s chunk at " PTR_FORMAT " (word size " SIZE_FORMAT ") to freelist.",
+ chunk_size_name(index), p2i(chunk), chunk->word_size());
+ }
+ }
+ chunk->container()->dec_container_count();
+ do_update_in_use_info_for_chunk(chunk, false);
+
+ // Chunk has been added; update counters.
+ account_for_added_chunk(chunk);
+
+ // Attempt coalesce returned chunks with its neighboring chunks:
+ // if this chunk is small or special, attempt to coalesce to a medium chunk.
+ if (index == SmallIndex || index == SpecializedIndex) {
+ if (!attempt_to_coalesce_around_chunk(chunk, MediumIndex)) {
+ // This did not work. But if this chunk is special, we still may form a small chunk?
+ if (index == SpecializedIndex) {
+ if (!attempt_to_coalesce_around_chunk(chunk, SmallIndex)) {
+ // give up.
+ }
+ }
+ }
+ }
+
+}
+
+void ChunkManager::return_chunk_list(ChunkIndex index, Metachunk* chunks) {
+ index_bounds_check(index);
+ if (chunks == NULL) {
+ return;
+ }
+ // tracing
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("returning list of %s chunks...", chunk_size_name(index));
+ }
+
+ unsigned num_chunks_returned = 0;
+ size_t size_chunks_returned = 0;
+ Metachunk* cur = chunks;
+ while (cur != NULL) {
+ // Capture the next link before it is changed
+ // by the call to return_chunk_at_head();
+ Metachunk* next = cur->next();
+ // tracing
+ num_chunks_returned ++;
+ size_chunks_returned += cur->word_size();
+
+ return_single_chunk(index, cur);
+ cur = next;
+ }
+ // tracing
+ if (TraceMetadataChunkAllocation) {
+ gclog_or_tty->print_cr("returned %u %s chunks to freelist, total word size " SIZE_FORMAT ".",
+ num_chunks_returned, chunk_size_name(index), size_chunks_returned);
+ if (index != HumongousIndex) {
+ gclog_or_tty->print_cr("updated freelist count: " SIZE_FORMAT ".", free_chunks(index)->size());
+ } else {
+ gclog_or_tty->print_cr("updated dictionary count " SIZE_FORMAT ".", _humongous_dictionary.total_count());
+ }
+ }
+}
+
void ChunkManager::print_on(outputStream* out) const {
if (PrintFLSStatistics != 0) {
_humongous_dictionary.report_statistics();
@@ -2394,31 +3568,6 @@ void SpaceManager::initialize() {
}
}
-void ChunkManager::return_chunks(ChunkIndex index, Metachunk* chunks) {
- if (chunks == NULL) {
- return;
- }
- ChunkList* list = free_chunks(index);
- assert(list->size() == chunks->word_size(), "Mismatch in chunk sizes");
- assert_lock_strong(SpaceManager::expand_lock());
- Metachunk* cur = chunks;
-
- // This returns chunks one at a time. If a new
- // class List can be created that is a base class
- // of FreeList then something like FreeList::prepend()
- // can be used in place of this loop
- while (cur != NULL) {
- assert(cur->container() != NULL, "Container should have been set");
- cur->container()->dec_container_count();
- // Capture the next link before it is changed
- // by the call to return_chunk_at_head();
- Metachunk* next = cur->next();
- DEBUG_ONLY(cur->set_is_tagged_free(true);)
- list->return_chunk_at_head(cur);
- cur = next;
- }
-}
-
SpaceManager::~SpaceManager() {
// This call this->_lock which can't be done while holding expand_lock()
assert(sum_capacity_in_chunks_in_use() == allocated_chunks_words(),
@@ -2429,6 +3578,11 @@ SpaceManager::~SpaceManager() {
MutexLockerEx fcl(SpaceManager::expand_lock(),
Mutex::_no_safepoint_check_flag);
+ assert(sum_count_in_chunks_in_use() == allocated_chunks_count(),
+ err_msg("sum_count_in_chunks_in_use() " SIZE_FORMAT
+ " allocated_chunks_count() " SIZE_FORMAT,
+ sum_count_in_chunks_in_use(), allocated_chunks_count()));
+
chunk_manager()->slow_locked_verify();
dec_total_from_size_metrics();
@@ -2436,112 +3590,27 @@ SpaceManager::~SpaceManager() {
if (TraceMetadataChunkAllocation && Verbose) {
gclog_or_tty->print_cr("~SpaceManager(): " PTR_FORMAT, this);
locked_print_chunks_in_use_on(gclog_or_tty);
+ if (block_freelists() != NULL) {
+ block_freelists()->print_on(gclog_or_tty);
+ }
}
- // Do not mangle freed Metachunks. The chunk size inside Metachunks
- // is during the freeing of a VirtualSpaceNodes.
-
- // Have to update before the chunks_in_use lists are emptied
- // below.
- chunk_manager()->inc_free_chunks_total(allocated_chunks_words(),
- sum_count_in_chunks_in_use());
-
// Add all the chunks in use by this space manager
// to the global list of free chunks.
// Follow each list of chunks-in-use and add them to the
// free lists. Each list is NULL terminated.
- for (ChunkIndex i = ZeroIndex; i < HumongousIndex; i = next_chunk_index(i)) {
- if (TraceMetadataChunkAllocation && Verbose) {
- gclog_or_tty->print_cr("returned %d %s chunks to freelist",
- sum_count_in_chunks_in_use(i),
- chunk_size_name(i));
- }
+ for (ChunkIndex i = ZeroIndex; i <= HumongousIndex; i = next_chunk_index(i)) {
Metachunk* chunks = chunks_in_use(i);
- chunk_manager()->return_chunks(i, chunks);
+ chunk_manager()->return_chunk_list(i, chunks);
set_chunks_in_use(i, NULL);
- if (TraceMetadataChunkAllocation && Verbose) {
- gclog_or_tty->print_cr("updated freelist count %d %s",
- chunk_manager()->free_chunks(i)->count(),
- chunk_size_name(i));
- }
- assert(i != HumongousIndex, "Humongous chunks are handled explicitly later");
}
- // The medium chunk case may be optimized by passing the head and
- // tail of the medium chunk list to add_at_head(). The tail is often
- // the current chunk but there are probably exceptions.
-
- // Humongous chunks
- if (TraceMetadataChunkAllocation && Verbose) {
- gclog_or_tty->print_cr("returned %d %s humongous chunks to dictionary",
- sum_count_in_chunks_in_use(HumongousIndex),
- chunk_size_name(HumongousIndex));
- gclog_or_tty->print("Humongous chunk dictionary: ");
- }
- // Humongous chunks are never the current chunk.
- Metachunk* humongous_chunks = chunks_in_use(HumongousIndex);
- while (humongous_chunks != NULL) {
-#ifdef ASSERT
- humongous_chunks->set_is_tagged_free(true);
-#endif
- if (TraceMetadataChunkAllocation && Verbose) {
- gclog_or_tty->print(PTR_FORMAT " (" SIZE_FORMAT ") ",
- humongous_chunks,
- humongous_chunks->word_size());
- }
- assert(humongous_chunks->word_size() == (size_t)
- align_size_up(humongous_chunks->word_size(),
- smallest_chunk_size()),
- err_msg("Humongous chunk size is wrong: word size " SIZE_FORMAT
- " granularity %d",
- humongous_chunks->word_size(), smallest_chunk_size()));
- Metachunk* next_humongous_chunks = humongous_chunks->next();
- humongous_chunks->container()->dec_container_count();
- chunk_manager()->humongous_dictionary()->return_chunk(humongous_chunks);
- humongous_chunks = next_humongous_chunks;
- }
- if (TraceMetadataChunkAllocation && Verbose) {
- gclog_or_tty->cr();
- gclog_or_tty->print_cr("updated dictionary count %d %s",
- chunk_manager()->humongous_dictionary()->total_count(),
- chunk_size_name(HumongousIndex));
- }
chunk_manager()->slow_locked_verify();
}
-const char* SpaceManager::chunk_size_name(ChunkIndex index) const {
- switch (index) {
- case SpecializedIndex:
- return "Specialized";
- case SmallIndex:
- return "Small";
- case MediumIndex:
- return "Medium";
- case HumongousIndex:
- return "Humongous";
- default:
- return NULL;
- }
-}
-
-ChunkIndex ChunkManager::list_index(size_t size) {
- if (free_chunks(SpecializedIndex)->size() == size) {
- return SpecializedIndex;
- }
- if (free_chunks(SmallIndex)->size() == size) {
- return SmallIndex;
- }
- if (free_chunks(MediumIndex)->size() == size) {
- return MediumIndex;
- }
-
- assert(size > free_chunks(MediumIndex)->size(), "Not a humongous chunk");
- return HumongousIndex;
-}
-
void SpaceManager::deallocate(MetaWord* p, size_t word_size) {
assert_lock_strong(_lock);
size_t raw_word_size = get_raw_word_size(word_size);
@@ -2693,8 +3762,8 @@ void SpaceManager::verify() {
for (ChunkIndex i = ZeroIndex; i < NumberOfInUseLists; i = next_chunk_index(i)) {
Metachunk* curr = chunks_in_use(i);
while (curr != NULL) {
- curr->verify();
- verify_chunk_size(curr);
+ DEBUG_ONLY(do_verify_chunk(curr);)
+ assert(curr->is_tagged_free() == false, "Chunk should be tagged as in use.");
curr = curr->next();
}
}
@@ -2767,7 +3836,7 @@ void SpaceManager::mangle_freed_chunks() {
for (Metachunk* curr = chunks_in_use(index);
curr != NULL;
curr = curr->next()) {
- curr->mangle();
+ curr->mangle(uninitMetaWordVal);
}
}
}
@@ -2988,9 +4057,9 @@ void MetaspaceAux::print_on(outputStream* out, Metaspace::MetadataType mdtype) {
size_t free_bytes = free_bytes_slow(mdtype);
size_t used_and_free = used_bytes + free_bytes +
free_chunks_capacity_bytes;
- out->print_cr(" Chunk accounting: used in chunks " SIZE_FORMAT
+ out->print_cr(" Chunk accounting: (used in chunks " SIZE_FORMAT
"K + unused in chunks " SIZE_FORMAT "K + "
- " capacity in free chunks " SIZE_FORMAT "K = " SIZE_FORMAT
+ " capacity in free chunks " SIZE_FORMAT "K) = " SIZE_FORMAT
"K capacity in allocated chunks " SIZE_FORMAT "K",
used_bytes / K,
free_bytes / K,
@@ -3255,6 +4324,31 @@ void MetaspaceAux::dump(outputStream* out) {
print_waste(out);
}
+// Prints an ASCII representation of the given space.
+void MetaspaceAux::print_metaspace_map(outputStream* out, Metaspace::MetadataType mdtype) {
+ MutexLockerEx cl(SpaceManager::expand_lock(), Mutex::_no_safepoint_check_flag);
+ const bool for_class = mdtype == Metaspace::ClassType ? true : false;
+ VirtualSpaceList* const vsl = for_class ? Metaspace::class_space_list() : Metaspace::space_list();
+ if (vsl != NULL) {
+ if (for_class) {
+ if (!Metaspace::using_class_space()) {
+ out->print_cr("No Class Space.");
+ return;
+ }
+ out->print_raw("---- Metaspace Map (Class Space) ----");
+ } else {
+ out->print_raw("---- Metaspace Map (Non-Class Space) ----");
+ }
+ // Print legend:
+ out->cr();
+ out->print_cr("Chunk Types (uppercase chunks are in use): x-specialized, s-small, m-medium, h-humongous.");
+ out->cr();
+ VirtualSpaceList* const vsl = for_class ? Metaspace::class_space_list() : Metaspace::space_list();
+ vsl->print_map(out);
+ out->cr();
+ }
+}
+
void MetaspaceAux::verify_free_chunks() {
Metaspace::chunk_manager_metadata()->verify();
if (Metaspace::using_class_space()) {
@@ -3523,7 +4617,7 @@ void Metaspace::initialize_class_space(ReservedSpace rs) {
err_msg(SIZE_FORMAT " != " UINTX_FORMAT, rs.size(), CompressedClassSpaceSize));
assert(using_class_space(), "Must be using class space");
_class_space_list = new VirtualSpaceList(rs);
- _chunk_manager_class = new ChunkManager(ClassSpecializedChunk, ClassSmallChunk, ClassMediumChunk);
+ _chunk_manager_class = new ChunkManager(true/*is_class*/);
if (!_class_space_list->initialization_succeeded()) {
vm_exit_during_initialization("Failed to setup compressed class space virtual space list.");
@@ -3627,7 +4721,7 @@ void Metaspace::global_initialize() {
cds_total = FileMapInfo::shared_spaces_size();
cds_total = align_size_up(cds_total, _reserve_alignment);
_space_list = new VirtualSpaceList(cds_total/wordSize);
- _chunk_manager_metadata = new ChunkManager(SpecializedChunk, SmallChunk, MediumChunk);
+ _chunk_manager_metadata = new ChunkManager(false/*metaspace*/);
if (!_space_list->initialization_succeeded()) {
vm_exit_during_initialization("Unable to dump shared archive.", NULL);
@@ -3777,7 +4871,7 @@ void Metaspace::global_initialize() {
// Initialize the list of virtual spaces.
_space_list = new VirtualSpaceList(word_size);
- _chunk_manager_metadata = new ChunkManager(SpecializedChunk, SmallChunk, MediumChunk);
+ _chunk_manager_metadata = new ChunkManager(false/*metaspace*/);
if (!_space_list->initialization_succeeded()) {
vm_exit_during_initialization("Unable to setup metadata virtual space list.", NULL);
@@ -4071,6 +5165,8 @@ void Metaspace::report_metadata_oome(ClassLoaderData* loader_data, size_t word_s
ChunkManager::print_all_chunkmanagers(gclog_or_tty);
}
+ MetaspaceAux::print_metaspace_map(gclog_or_tty, mdtype);
+
bool out_of_compressed_class_space = false;
if (is_class_space_allocation(mdtype)) {
Metaspace* metaspace = loader_data->metaspace_non_null();
@@ -4236,6 +5332,24 @@ void Metaspace::dump(outputStream* const out) const {
}
}
+#ifdef ASSERT
+static void do_verify_chunk(Metachunk* chunk) {
+ guarantee(chunk != NULL, "Sanity");
+ // Verify chunk itself; then verify that it is consistent with the
+ // occupany map of its containing node.
+ chunk->verify();
+ VirtualSpaceNode* const vsn = chunk->container();
+ OccupancyMap* const ocmap = vsn->occupancy_map();
+ ocmap->verify_for_chunk(chunk);
+}
+#endif
+
+static void do_update_in_use_info_for_chunk(Metachunk* chunk, bool inuse) {
+ chunk->set_is_tagged_free(!inuse);
+ OccupancyMap* const ocmap = chunk->container()->occupancy_map();
+ ocmap->set_region_in_use((MetaWord*)chunk, chunk->word_size(), inuse);
+}
+
/////////////// Unit tests ///////////////
#ifndef PRODUCT
@@ -4326,16 +5440,16 @@ class TestVirtualSpaceNodeTest {
STATIC_ASSERT(SmallChunk % SpecializedChunk == 0);
{ // No committed memory in VSN
- ChunkManager cm(SpecializedChunk, SmallChunk, MediumChunk);
- VirtualSpaceNode vsn(vsn_test_size_bytes);
+ ChunkManager cm(false);
+ VirtualSpaceNode vsn(false, vsn_test_size_bytes);
vsn.initialize();
vsn.retire(&cm);
assert(cm.sum_free_chunks_count() == 0, "did not commit any memory in the VSN");
}
{ // All of VSN is committed, half is used by chunks
- ChunkManager cm(SpecializedChunk, SmallChunk, MediumChunk);
- VirtualSpaceNode vsn(vsn_test_size_bytes);
+ ChunkManager cm(false);
+ VirtualSpaceNode vsn(false, vsn_test_size_bytes);
vsn.initialize();
vsn.expand_by(vsn_test_size_words, vsn_test_size_words);
vsn.get_chunk_vs(MediumChunk);
@@ -4349,8 +5463,8 @@ class TestVirtualSpaceNodeTest {
// This doesn't work for systems with vm_page_size >= 16K.
if (page_chunks < MediumChunk) {
// 4 pages of VSN is committed, some is used by chunks
- ChunkManager cm(SpecializedChunk, SmallChunk, MediumChunk);
- VirtualSpaceNode vsn(vsn_test_size_bytes);
+ ChunkManager cm(false);
+ VirtualSpaceNode vsn(false, vsn_test_size_bytes);
vsn.initialize();
vsn.expand_by(page_chunks, page_chunks);
@@ -4370,8 +5484,8 @@ class TestVirtualSpaceNodeTest {
}
{ // Half of VSN is committed, a humongous chunk is used
- ChunkManager cm(SpecializedChunk, SmallChunk, MediumChunk);
- VirtualSpaceNode vsn(vsn_test_size_bytes);
+ ChunkManager cm(false);
+ VirtualSpaceNode vsn(false, vsn_test_size_bytes);
vsn.initialize();
vsn.expand_by(MediumChunk * 2, MediumChunk * 2);
vsn.get_chunk_vs(MediumChunk + SpecializedChunk); // Humongous chunks will be aligned up to MediumChunk + SpecializedChunk
@@ -4402,7 +5516,7 @@ class TestVirtualSpaceNodeTest {
static void test_is_available_positive() {
// Reserve some memory.
- VirtualSpaceNode vsn(os::vm_allocation_granularity());
+ VirtualSpaceNode vsn(false, os::vm_allocation_granularity());
assert(vsn.initialize(), "Failed to setup VirtualSpaceNode");
// Commit some memory.
@@ -4420,7 +5534,7 @@ class TestVirtualSpaceNodeTest {
static void test_is_available_negative() {
// Reserve some memory.
- VirtualSpaceNode vsn(os::vm_allocation_granularity());
+ VirtualSpaceNode vsn(false, os::vm_allocation_granularity());
assert(vsn.initialize(), "Failed to setup VirtualSpaceNode");
// Commit some memory.
@@ -4435,7 +5549,7 @@ class TestVirtualSpaceNodeTest {
static void test_is_available_overflow() {
// Reserve some memory.
- VirtualSpaceNode vsn(os::vm_allocation_granularity());
+ VirtualSpaceNode vsn(false, os::vm_allocation_granularity());
assert(vsn.initialize(), "Failed to setup VirtualSpaceNode");
// Commit some memory.
@@ -4460,11 +5574,240 @@ class TestVirtualSpaceNodeTest {
}
};
-void TestVirtualSpaceNode_test() {
- TestVirtualSpaceNodeTest::test();
- TestVirtualSpaceNodeTest::test_is_available();
+#ifdef DEBUG_VERBOSE
+
+struct chunkmanager_statistics_t {
+ int num_specialized_chunks;
+ int num_small_chunks;
+ int num_medium_chunks;
+ int num_humongous_chunks;
+};
+
+void test_metaspace_retrieve_chunkmanager_statistics(Metaspace::MetadataType mdType, chunkmanager_statistics_t* out) {
+ ChunkManager* const chunk_manager = Metaspace::get_chunk_manager(mdType);
+ ChunkManager::ChunkManagerStatistics stat;
+ chunk_manager->get_statistics(&stat);
+ out->num_specialized_chunks = (int)stat.num_by_type[SpecializedIndex];
+ out->num_small_chunks = (int)stat.num_by_type[SmallIndex];
+ out->num_medium_chunks = (int)stat.num_by_type[MediumIndex];
+ out->num_humongous_chunks = (int)stat.num_humongous_chunks;
+}
+
+static void print_chunkmanager_statistics(outputStream* st, Metaspace::MetadataType mdType) {
+ chunkmanager_statistics_t stat;
+ test_metaspace_retrieve_chunkmanager_statistics(mdType, &stat);
+ st->print_cr("free chunks: %d / %d / %d / %d", stat.num_specialized_chunks, stat.num_small_chunks,
+ stat.num_medium_chunks, stat.num_humongous_chunks);
+}
+
+#endif // DEBUG_VERBOSE
+
+struct chunk_geometry_t {
+ size_t specialized_chunk_word_size;
+ size_t small_chunk_word_size;
+ size_t medium_chunk_word_size;
+};
+
+void test_metaspace_retrieve_chunk_geometry(Metaspace::MetadataType mdType, chunk_geometry_t* out) {
+ if (mdType == Metaspace::NonClassType) {
+ out->specialized_chunk_word_size = SpecializedChunk;
+ out->small_chunk_word_size = SmallChunk;
+ out->medium_chunk_word_size = MediumChunk;
+ } else {
+ out->specialized_chunk_word_size = ClassSpecializedChunk;
+ out->small_chunk_word_size = ClassSmallChunk;
+ out->medium_chunk_word_size = ClassMediumChunk;
+ }
+}
+
+#define NUM_PARALLEL_METASPACES 50
+#define MAX_PER_METASPACE_ALLOCATION_WORDSIZE (512 * K)
+
+class MetaspaceAllocationTest {
+protected:
+
+ struct {
+ size_t allocated;
+ Mutex* lock;
+ Metaspace* space;
+ bool is_empty() const { return allocated == 0; }
+ bool is_full() const { return allocated >= MAX_PER_METASPACE_ALLOCATION_WORDSIZE; }
+ } _spaces[NUM_PARALLEL_METASPACES];
+
+ chunk_geometry_t _chunk_geometry;
+
+ void create_space(int i) {
+ assert(i >= 0 && i < NUM_PARALLEL_METASPACES, "Sanity");
+ assert(_spaces[i].space == NULL && _spaces[i].allocated == 0, "Sanity");
+ if (_spaces[i].lock == NULL) {
+ _spaces[i].lock = new Mutex(Monitor::native, "gtest-MetaspaceAllocationTest-lock", false);
+ assert(_spaces[i].lock != NULL, "_spaces[i].lock is NULL");
+ }
+ // Let every ~10th space be an anonymous one to test different allocation patterns.
+ const Metaspace::MetaspaceType msType = (os::random() % 100 < 10) ?
+ Metaspace::AnonymousMetaspaceType : Metaspace::StandardMetaspaceType;
+ _spaces[i].space = new Metaspace(_spaces[i].lock, msType);
+ _spaces[i].allocated = 0;
+ assert(_spaces[i].space != NULL, "_spaces[i].space is NULL");
+ }
+
+ // Returns the index of a random space where index is [0..metaspaces) and which is
+ // empty, non-empty or full.
+ // Returns -1 if no matching space exists.
+ enum fillgrade { fg_empty, fg_non_empty, fg_full };
+ int get_random_matching_space(int metaspaces, fillgrade fg) {
+ const int start_index = os::random() % metaspaces;
+ int i = start_index;
+ do {
+ if (fg == fg_empty && _spaces[i].is_empty()) {
+ return i;
+ } else if ((fg == fg_full && _spaces[i].is_full()) ||
+ (fg == fg_non_empty && !_spaces[i].is_full() && !_spaces[i].is_empty())) {
+ return i;
+ }
+ i ++;
+ if (i == metaspaces) {
+ i = 0;
+ }
+ } while (i != start_index);
+ return -1;
+ }
+
+ int get_random_emtpy_space(int metaspaces) { return get_random_matching_space(metaspaces, fg_empty); }
+ int get_random_non_emtpy_space(int metaspaces) { return get_random_matching_space(metaspaces, fg_non_empty); }
+ int get_random_full_space(int metaspaces) { return get_random_matching_space(metaspaces, fg_full); }
+
+public:
+
+ virtual void SetUp() {
+ ::memset(_spaces, 0, sizeof(_spaces));
+ test_metaspace_retrieve_chunk_geometry(Metaspace::NonClassType, &_chunk_geometry);
+ }
+
+ virtual void TearDown() {
+ for (int i = 0; i < NUM_PARALLEL_METASPACES; i ++) {
+ if (_spaces[i].space != NULL) {
+ delete _spaces[i].space;
+ delete _spaces[i].lock;
+ }
+ }
+ }
+
+ void do_test(Metaspace::MetadataType mdType, int metaspaces, int phases, int allocs_per_phase,
+ float probability_for_large_allocations // 0.0-1.0
+ ) {
+ // Alternate between breathing in (allocating n blocks for a random Metaspace) and
+ // breathing out (deleting a random Metaspace). The intent is to stress the coalescation
+ // and splitting of free chunks.
+ int phases_done = 0;
+ bool allocating = true;
+ while (phases_done < phases) {
+ bool force_switch = false;
+ if (allocating) {
+ // Allocate space from metaspace, with a preference for completely empty spaces. This
+ // should provide a good mixture of metaspaces in the virtual space.
+ int index = get_random_emtpy_space(metaspaces);
+ if (index == -1) {
+ index = get_random_non_emtpy_space(metaspaces);
+ }
+ if (index == -1) {
+ // All spaces are full, switch to freeing.
+ force_switch = true;
+ } else {
+ // create space if it does not yet exist.
+ if (_spaces[index].space == NULL) {
+ create_space(index);
+ }
+ // Allocate a bunch of blocks from it. Mostly small stuff but mix in large allocations
+ // to force humongous chunk allocations.
+ int allocs_done = 0;
+ while (allocs_done < allocs_per_phase && !_spaces[index].is_full()) {
+ size_t size = 0;
+ int r = os::random() % 1000;
+ if ((float)r < probability_for_large_allocations * 1000.0) {
+ size = (os::random() % _chunk_geometry.medium_chunk_word_size) + _chunk_geometry.medium_chunk_word_size;
+ } else {
+ size = os::random() % 64;
+ }
+ MetaWord* const p = _spaces[index].space->allocate(size, mdType);
+ if (p == NULL) {
+ // We very probably did hit the metaspace "until-gc" limit.
+#ifdef DEBUG_VERBOSE
+ tty->print_cr("OOM for " SIZE_FORMAT " words. ", size);
+#endif
+ // Just switch to deallocation and resume tests.
+ force_switch = true;
+ break;
+ } else {
+ _spaces[index].allocated += size;
+ allocs_done ++;
+ }
+ }
+ }
+ } else {
+ // freeing: find a metaspace and delete it, with preference for completely filled spaces.
+ int index = get_random_full_space(metaspaces);
+ if (index == -1) {
+ index = get_random_non_emtpy_space(metaspaces);
+ }
+ if (index == -1) {
+ force_switch = true;
+ } else {
+ assert(_spaces[index].space != NULL && _spaces[index].allocated > 0, "Sanity");
+ delete _spaces[index].space;
+ _spaces[index].space = NULL;
+ _spaces[index].allocated = 0;
+ }
+ }
+
+ if (force_switch) {
+ allocating = !allocating;
+ } else {
+ // periodically switch between allocating and freeing, but prefer allocation because
+ // we want to intermingle allocations of multiple metaspaces.
+ allocating = os::random() % 5 < 4;
+ }
+ phases_done ++;
+#ifdef DEBUG_VERBOSE
+ int metaspaces_in_use = 0;
+ size_t total_allocated = 0;
+ for (int i = 0; i < metaspaces; i ++) {
+ if (_spaces[i].allocated > 0) {
+ total_allocated += _spaces[i].allocated;
+ metaspaces_in_use ++;
+ }
+ }
+ tty->print("%u:\tspaces: %d total words: " SIZE_FORMAT "\t\t\t", phases_done, metaspaces_in_use, total_allocated);
+ print_chunkmanager_statistics(tty, mdType);
+#endif
+ }
+#ifdef DEBUG_VERBOSE
+ tty->print_cr("Test finished. ");
+ MetaspaceAux::print_metaspace_map(tty, mdType);
+ print_chunkmanager_statistics(tty, mdType);
+#endif
+ }
+};
+
+void MetaspaceAllocation_test(Metaspace::MetadataType mdType, int metaspaces, int phases, int allocs_per_phase, float probability_for_large_allocations) {
+ MetaspaceAllocationTest test;
+ test.SetUp();
+ test.do_test(mdType, metaspaces, phases, allocs_per_phase, probability_for_large_allocations);
+ test.TearDown();
}
+void run_MetaspaceAllocation_test(){
+ MetaspaceAllocation_test(Metaspace::NonClassType, 1, 1000, 100, 0);
+ MetaspaceAllocation_test(Metaspace::ClassType, 1, 1000, 100, 0);
+ MetaspaceAllocation_test(Metaspace::NonClassType, NUM_PARALLEL_METASPACES, 100, 1000, 0.0);
+ MetaspaceAllocation_test(Metaspace::ClassType, NUM_PARALLEL_METASPACES, 100, 1000, 0.0);
+ MetaspaceAllocation_test(Metaspace::NonClassType, NUM_PARALLEL_METASPACES, 100, 1000, .006f);
+}
+
+#endif // !PRODUCT
+
+#ifdef ASSERT
+
// The following test is placed here instead of a gtest / unittest file
// because the ChunkManager class is only available in this file.
class SpaceManagerTest : AllStatic {
@@ -4517,7 +5860,7 @@ void SpaceManager_test_adjust_initial_chunk_size() {
// The following test is placed here instead of a gtest / unittest file
// because the ChunkManager class is only available in this file.
void ChunkManager_test_list_index() {
- ChunkManager manager(ClassSpecializedChunk, ClassSmallChunk, ClassMediumChunk);
+ ChunkManager manager(true);
// Test previous bug where a query for a humongous class metachunk,
// incorrectly matched the non-class medium metachunk size.
@@ -4550,4 +5893,5 @@ void ChunkManager_test_list_index() {
}
}
-#endif
+#endif // ASSERT
+
diff --git a/hotspot/src/share/vm/memory/metaspace.hpp b/hotspot/src/share/vm/memory/metaspace.hpp
index ff1b23299..11944d393 100644
--- a/hotspot/src/share/vm/memory/metaspace.hpp
+++ b/hotspot/src/share/vm/memory/metaspace.hpp
@@ -147,11 +147,6 @@ class Metaspace : public CHeapObj<mtClass> {
return mdtype == ClassType ? class_vsm() : vsm();
}
- // Allocate space for metadata of type mdtype. This is space
- // within a Metachunk and is used by
- // allocate(ClassLoaderData*, size_t, bool, MetadataType, TRAPS)
- MetaWord* allocate(size_t word_size, MetadataType mdtype);
-
// Virtual Space lists for both classes and other metadata
static VirtualSpaceList* _space_list;
static VirtualSpaceList* _class_space_list;
@@ -162,6 +157,10 @@ class Metaspace : public CHeapObj<mtClass> {
static const MetaspaceTracer* _tracer;
public:
+ // Allocate space for metadata of type mdtype. This is space
+ // within a Metachunk and is used by
+ // allocate(ClassLoaderData*, size_t, bool, MetadataType, TRAPS)
+ MetaWord* allocate(size_t word_size, MetadataType mdtype);
static VirtualSpaceList* space_list() { return _space_list; }
static VirtualSpaceList* class_space_list() { return _class_space_list; }
static VirtualSpaceList* get_space_list(MetadataType mdtype) {
@@ -176,6 +175,11 @@ class Metaspace : public CHeapObj<mtClass> {
return mdtype == ClassType ? chunk_manager_class() : chunk_manager_metadata();
}
+ // convenience function
+ static ChunkManager* get_chunk_manager(bool is_class) {
+ return is_class ? chunk_manager_class() : chunk_manager_metadata();
+ }
+
static const MetaspaceTracer* tracer() { return _tracer; }
private:
@@ -386,6 +390,10 @@ class MetaspaceAux : AllStatic {
static void print_class_waste(outputStream* out);
static void print_waste(outputStream* out);
+
+ // Prints an ASCII representation of the given space.
+ static void print_metaspace_map(outputStream* out, Metaspace::MetadataType mdtype);
+
static void dump(outputStream* out);
static void verify_free_chunks();
// Checks that the values returned by allocated_capacity_bytes() and
diff --git a/hotspot/src/share/vm/prims/jni.cpp b/hotspot/src/share/vm/prims/jni.cpp
index dccbf1e8a..953300ebc 100644
--- a/hotspot/src/share/vm/prims/jni.cpp
+++ b/hotspot/src/share/vm/prims/jni.cpp
@@ -5112,9 +5112,9 @@ void TestReservedSpace_test();
void TestReserveMemorySpecial_test();
void TestVirtualSpace_test();
void TestMetaspaceAux_test();
+void run_MetaspaceAllocation_test();
void SpaceManager_test_adjust_initial_chunk_size();
void TestMetachunk_test();
-void TestVirtualSpaceNode_test();
void TestNewSize_test();
void TestKlass_test();
void Test_linked_list();
@@ -5137,8 +5137,8 @@ void execute_internal_vm_tests() {
run_unit_test(TestReserveMemorySpecial_test());
run_unit_test(TestVirtualSpace_test());
run_unit_test(TestMetaspaceAux_test());
+ run_unit_test(run_MetaspaceAllocation_test());
run_unit_test(TestMetachunk_test());
- run_unit_test(TestVirtualSpaceNode_test());
run_unit_test(GlobalDefinitions::test_globals());
run_unit_test(GlobalDefinitions::test_proper_unit());
run_unit_test(GCTimerAllTest::all());
diff --git a/hotspot/src/share/vm/utilities/globalDefinitions.hpp b/hotspot/src/share/vm/utilities/globalDefinitions.hpp
index 12eea20fc..efa430663 100644
--- a/hotspot/src/share/vm/utilities/globalDefinitions.hpp
+++ b/hotspot/src/share/vm/utilities/globalDefinitions.hpp
@@ -1079,6 +1079,7 @@ const int badHandleValue = 0xBC; // value used to zap
const int badResourceValue = 0xAB; // value used to zap resource area
const int freeBlockPad = 0xBA; // value used to pad freed blocks.
const int uninitBlockPad = 0xF1; // value used to zap newly malloc'd blocks.
+const juint uninitMetaWordVal= 0xf7f7f7f7; // value used to zap newly allocated metachunk
const intptr_t badJNIHandleVal = (intptr_t) CONST64(0xFEFEFEFEFEFEFEFE); // value used to zap jni handle area
const juint badHeapWordVal = 0xBAADBABE; // value used to zap heap after GC
const juint badMetaWordVal = 0xBAADFADE; // value used to zap metadata heap after GC
--
2.22.0
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