jdk8-mips64-public/hotspot: comparison src/share/vm/gc_implementation/g1/g1StringDedupTable.cpp

-:6e7e363c5a8f
+:595c0f60d50d
+/*
+* Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
+* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+*
+* This code is free software; you can redistribute it and/or modify it
+* under the terms of the GNU General Public License version 2 only, as
+* published by the Free Software Foundation.
+*
+* This code is distributed in the hope that it will be useful, but WITHOUT
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+* version 2 for more details (a copy is included in the LICENSE file that
+* accompanied this code).
+*
+* You should have received a copy of the GNU General Public License version
+* 2 along with this work; if not, write to the Free Software Foundation,
+* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+*
+* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+* or visit www.oracle.com if you need additional information or have any
+* questions.
+*
+*/
+#include "precompiled.hpp"
+#include "classfile/altHashing.hpp"
+#include "classfile/javaClasses.hpp"
+#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
+#include "gc_implementation/g1/g1SATBCardTableModRefBS.hpp"
+#include "gc_implementation/g1/g1StringDedupTable.hpp"
+#include "memory/gcLocker.hpp"
+#include "memory/padded.inline.hpp"
+#include "oops/typeArrayOop.hpp"
+#include "runtime/mutexLocker.hpp"
+//
+// Freelist in the deduplication table entry cache. Links table
+// entries together using their _next fields.
+//
+class G1StringDedupEntryFreeList : public CHeapObj<mtGC> {
+private:
+G1StringDedupEntry* _list;
+size_t              _length;
+public:
+G1StringDedupEntryFreeList() :
+_list(NULL),
+_length(0) {
+}
+void add(G1StringDedupEntry* entry) {
+entry->set_next(_list);
+_list = entry;
+_length++;
+}
+G1StringDedupEntry* remove() {
+G1StringDedupEntry* entry = _list;
+if (entry != NULL) {
+_list = entry->next();
+_length--;
+}
+return entry;
+}
+size_t length() {
+return _length;
+}
+};
+//
+// Cache of deduplication table entries. This cache provides fast allocation and
+// reuse of table entries to lower the pressure on the underlying allocator.
+// But more importantly, it provides fast/deferred freeing of table entries. This
+// is important because freeing of table entries is done during stop-the-world
+// phases and it is not uncommon for large number of entries to be freed at once.
+// Tables entries that are freed during these phases are placed onto a freelist in
+// the cache. The deduplication thread, which executes in a concurrent phase, will
+// later reuse or free the underlying memory for these entries.
+//
+// The cache allows for single-threaded allocations and multi-threaded frees.
+// Allocations are synchronized by StringDedupTable_lock as part of a table
+// modification.
+//
+class G1StringDedupEntryCache : public CHeapObj<mtGC> {
+private:
+// One freelist per GC worker to allow lock less freeing of
+// entries while doing a parallel scan of the table. Using
+// PaddedEnd to avoid false sharing.
+PaddedEnd<G1StringDedupEntryFreeList>* _lists;
+size_t                                 _nlists;
+public:
+G1StringDedupEntryCache();
+~G1StringDedupEntryCache();
+// Get a table entry from the cache freelist, or allocate a new
+// entry if the cache is empty.
+G1StringDedupEntry* alloc();
+// Insert a table entry into the cache freelist.
+void free(G1StringDedupEntry* entry, uint worker_id);
+// Returns current number of entries in the cache.
+size_t size();
+// If the cache has grown above the given max size, trim it down
+// and deallocate the memory occupied by trimmed of entries.
+void trim(size_t max_size);
+};
+G1StringDedupEntryCache::G1StringDedupEntryCache() {
+_nlists = MAX2(ParallelGCThreads, (size_t)1);
+_lists = PaddedArray<G1StringDedupEntryFreeList, mtGC>::create_unfreeable((uint)_nlists);
+}
+G1StringDedupEntryCache::~G1StringDedupEntryCache() {
+ShouldNotReachHere();
+}
+G1StringDedupEntry* G1StringDedupEntryCache::alloc() {
+for (size_t i = 0; i < _nlists; i++) {
+G1StringDedupEntry* entry = _lists[i].remove();
+if (entry != NULL) {
+return entry;
+}
+}
+return new G1StringDedupEntry();
+}
+void G1StringDedupEntryCache::free(G1StringDedupEntry* entry, uint worker_id) {
+assert(entry->obj() != NULL, "Double free");
+assert(worker_id < _nlists, "Invalid worker id");
+entry->set_obj(NULL);
+entry->set_hash(0);
+_lists[worker_id].add(entry);
+}
+size_t G1StringDedupEntryCache::size() {
+size_t size = 0;
+for (size_t i = 0; i < _nlists; i++) {
+size += _lists[i].length();
+}
+return size;
+}
+void G1StringDedupEntryCache::trim(size_t max_size) {
+size_t cache_size = 0;
+for (size_t i = 0; i < _nlists; i++) {
+G1StringDedupEntryFreeList* list = &_lists[i];
+cache_size += list->length();
+while (cache_size > max_size) {
+G1StringDedupEntry* entry = list->remove();
+assert(entry != NULL, "Should not be null");
+cache_size--;
+delete entry;
+}
+}
+}
+G1StringDedupTable*      G1StringDedupTable::_table = NULL;
+G1StringDedupEntryCache* G1StringDedupTable::_entry_cache = NULL;
+const size_t             G1StringDedupTable::_min_size = (1 << 10);   // 1024
+const size_t             G1StringDedupTable::_max_size = (1 << 24);   // 16777216
+const double             G1StringDedupTable::_grow_load_factor = 2.0; // Grow table at 200% load
+const double             G1StringDedupTable::_shrink_load_factor = _grow_load_factor / 3.0; // Shrink table at 67% load
+const double             G1StringDedupTable::_max_cache_factor = 0.1; // Cache a maximum of 10% of the table size
+const uintx              G1StringDedupTable::_rehash_multiple = 60;   // Hash bucket has 60 times more collisions than expected
+const uintx              G1StringDedupTable::_rehash_threshold = (uintx)(_rehash_multiple * _grow_load_factor);
+uintx                    G1StringDedupTable::_entries_added = 0;
+uintx                    G1StringDedupTable::_entries_removed = 0;
+uintx                    G1StringDedupTable::_resize_count = 0;
+uintx                    G1StringDedupTable::_rehash_count = 0;
+G1StringDedupTable::G1StringDedupTable(size_t size, jint hash_seed) :
+_size(size),
+_entries(0),
+_grow_threshold((uintx)(size * _grow_load_factor)),
+_shrink_threshold((uintx)(size * _shrink_load_factor)),
+_rehash_needed(false),
+_hash_seed(hash_seed) {
+assert(is_power_of_2(size), "Table size must be a power of 2");
+_buckets = NEW_C_HEAP_ARRAY(G1StringDedupEntry*, _size, mtGC);
+memset(_buckets, 0, _size * sizeof(G1StringDedupEntry*));
+}
+G1StringDedupTable::~G1StringDedupTable() {
+FREE_C_HEAP_ARRAY(G1StringDedupEntry*, _buckets, mtGC);
+}
+void G1StringDedupTable::create() {
+assert(_table == NULL, "One string deduplication table allowed");
+_entry_cache = new G1StringDedupEntryCache();
+_table = new G1StringDedupTable(_min_size);
+}
+void G1StringDedupTable::add(typeArrayOop value, unsigned int hash, G1StringDedupEntry** list) {
+G1StringDedupEntry* entry = _entry_cache->alloc();
+entry->set_obj(value);
+entry->set_hash(hash);
+entry->set_next(*list);
+*list = entry;
+_entries++;
+}
+void G1StringDedupTable::remove(G1StringDedupEntry** pentry, uint worker_id) {
+G1StringDedupEntry* entry = *pentry;
+*pentry = entry->next();
+_entry_cache->free(entry, worker_id);
+}
+void G1StringDedupTable::transfer(G1StringDedupEntry** pentry, G1StringDedupTable* dest) {
+G1StringDedupEntry* entry = *pentry;
+*pentry = entry->next();
+unsigned int hash = entry->hash();
+size_t index = dest->hash_to_index(hash);
+G1StringDedupEntry** list = dest->bucket(index);
+entry->set_next(*list);
+*list = entry;
+}
+bool G1StringDedupTable::equals(typeArrayOop value1, typeArrayOop value2) {
+return (value1 == value2 ||
+(value1->length() == value2->length() &&
+(!memcmp(value1->base(T_CHAR),
+value2->base(T_CHAR),
+value1->length() * sizeof(jchar)))));
+}
+typeArrayOop G1StringDedupTable::lookup(typeArrayOop value, unsigned int hash,
+G1StringDedupEntry** list, uintx &count) {
+for (G1StringDedupEntry* entry = *list; entry != NULL; entry = entry->next()) {
+if (entry->hash() == hash) {
+typeArrayOop existing_value = entry->obj();
+if (equals(value, existing_value)) {
+// Match found
+return existing_value;
+}
+}
+count++;
+}
+// Not found
+return NULL;
+}
+typeArrayOop G1StringDedupTable::lookup_or_add_inner(typeArrayOop value, unsigned int hash) {
+size_t index = hash_to_index(hash);
+G1StringDedupEntry** list = bucket(index);
+uintx count = 0;
+// Lookup in list
+typeArrayOop existing_value = lookup(value, hash, list, count);
+// Check if rehash is needed
+if (count > _rehash_threshold) {
+_rehash_needed = true;
+}
+if (existing_value == NULL) {
+// Not found, add new entry
+add(value, hash, list);
+// Update statistics
+_entries_added++;
+}
+return existing_value;
+}
+unsigned int G1StringDedupTable::hash_code(typeArrayOop value) {
+unsigned int hash;
+int length = value->length();
+const jchar* data = (jchar*)value->base(T_CHAR);
+if (use_java_hash()) {
+hash = java_lang_String::hash_code(data, length);
+} else {
+hash = AltHashing::murmur3_32(_table->_hash_seed, data, length);
+}
+return hash;
+}
+void G1StringDedupTable::deduplicate(oop java_string, G1StringDedupStat& stat) {
+assert(java_lang_String::is_instance(java_string), "Must be a string");
+No_Safepoint_Verifier nsv;
+stat.inc_inspected();
+typeArrayOop value = java_lang_String::value(java_string);
+if (value == NULL) {
+// String has no value
+stat.inc_skipped();
+return;
+}
+unsigned int hash = 0;
+if (use_java_hash()) {
+// Get hash code from cache
+hash = java_lang_String::hash(java_string);
+}
+if (hash == 0) {
+// Compute hash
+hash = hash_code(value);
+stat.inc_hashed();
+}
+if (use_java_hash() && hash != 0) {
+// Store hash code in cache
+java_lang_String::set_hash(java_string, hash);
+}
+typeArrayOop existing_value = lookup_or_add(value, hash);
+if (existing_value == value) {
+// Same value, already known
+stat.inc_known();
+return;
+}
+// Get size of value array
+uintx size_in_bytes = value->size() * HeapWordSize;
+stat.inc_new(size_in_bytes);
+if (existing_value != NULL) {
+// Enqueue the reference to make sure it is kept alive. Concurrent mark might
+// otherwise declare it dead if there are no other strong references to this object.
+G1SATBCardTableModRefBS::enqueue(existing_value);
+// Existing value found, deduplicate string
+java_lang_String::set_value(java_string, existing_value);
+if (G1CollectedHeap::heap()->is_in_young(value)) {
+stat.inc_deduped_young(size_in_bytes);
+} else {
+stat.inc_deduped_old(size_in_bytes);
+}
+}
+}
+G1StringDedupTable* G1StringDedupTable::prepare_resize() {
+size_t size = _table->_size;
+// Check if the hashtable needs to be resized
+if (_table->_entries > _table->_grow_threshold) {
+// Grow table, double the size
+size *= 2;
+if (size > _max_size) {
+// Too big, don't resize
+return NULL;
+}
+} else if (_table->_entries < _table->_shrink_threshold) {
+// Shrink table, half the size
+size /= 2;
+if (size < _min_size) {
+// Too small, don't resize
+return NULL;
+}
+} else if (StringDeduplicationResizeALot) {
+// Force grow
+size *= 2;
+if (size > _max_size) {
+// Too big, force shrink instead
+size /= 4;
+}
+} else {
+// Resize not needed
+return NULL;
+}
+// Update statistics
+_resize_count++;
+// Allocate the new table. The new table will be populated by workers
+// calling unlink_or_oops_do() and finally installed by finish_resize().
+return new G1StringDedupTable(size, _table->_hash_seed);
+}
+void G1StringDedupTable::finish_resize(G1StringDedupTable* resized_table) {
+assert(resized_table != NULL, "Invalid table");
+resized_table->_entries = _table->_entries;
+// Free old table
+delete _table;
+// Install new table
+_table = resized_table;
+}
+void G1StringDedupTable::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl, uint worker_id) {
+// The table is divided into partitions to allow lock-less parallel processing by
+// multiple worker threads. A worker thread first claims a partition, which ensures
+// exclusive access to that part of the table, then continues to process it. To allow
+// shrinking of the table in parallel we also need to make sure that the same worker
+// thread processes all partitions where entries will hash to the same destination
+// partition. Since the table size is always a power of two and we always shrink by
+// dividing the table in half, we know that for a given partition there is only one
+// other partition whoes entries will hash to the same destination partition. That
+// other partition is always the sibling partition in the second half of the table.
+// For example, if the table is divided into 8 partitions, the sibling of partition 0
+// is partition 4, the sibling of partition 1 is partition 5, etc.
+size_t table_half = _table->_size / 2;
+// Let each partition be one page worth of buckets
+size_t partition_size = MIN2(table_half, os::vm_page_size() / sizeof(G1StringDedupEntry*));
+assert(table_half % partition_size == 0, "Invalid partition size");
+// Number of entries removed during the scan
+uintx removed = 0;
+for (;;) {
+// Grab next partition to scan
+size_t partition_begin = cl->claim_table_partition(partition_size);
+size_t partition_end = partition_begin + partition_size;
+if (partition_begin >= table_half) {
+// End of table
+break;
+}
+// Scan the partition followed by the sibling partition in the second half of the table
+removed += unlink_or_oops_do(cl, partition_begin, partition_end, worker_id);
+removed += unlink_or_oops_do(cl, table_half + partition_begin, table_half + partition_end, worker_id);
+}
+// Delayed update avoid contention on the table lock
+if (removed > 0) {
+MutexLockerEx ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag);
+_table->_entries -= removed;
+_entries_removed += removed;
+}
+}
+uintx G1StringDedupTable::unlink_or_oops_do(G1StringDedupUnlinkOrOopsDoClosure* cl,
+size_t partition_begin,
+size_t partition_end,
+uint worker_id) {
+uintx removed = 0;
+for (size_t bucket = partition_begin; bucket < partition_end; bucket++) {
+G1StringDedupEntry** entry = _table->bucket(bucket);
+while (*entry != NULL) {
+oop* p = (oop*)(*entry)->obj_addr();
+if (cl->is_alive(*p)) {
+cl->keep_alive(p);
+if (cl->is_resizing()) {
+// We are resizing the table, transfer entry to the new table
+_table->transfer(entry, cl->resized_table());
+} else {
+if (cl->is_rehashing()) {
+// We are rehashing the table, rehash the entry but keep it
+// in the table. We can't transfer entries into the new table
+// at this point since we don't have exclusive access to all
+// destination partitions. finish_rehash() will do a single
+// threaded transfer of all entries.
+typeArrayOop value = (typeArrayOop)*p;
+unsigned int hash = hash_code(value);
+(*entry)->set_hash(hash);
+}
+// Move to next entry
+entry = (*entry)->next_addr();
+}
+} else {
+// Not alive, remove entry from table
+_table->remove(entry, worker_id);
+removed++;
+}
+}
+}
+return removed;
+}
+G1StringDedupTable* G1StringDedupTable::prepare_rehash() {
+if (!_table->_rehash_needed && !StringDeduplicationRehashALot) {
+// Rehash not needed
+return NULL;
+}
+// Update statistics
+_rehash_count++;
+// Compute new hash seed
+_table->_hash_seed = AltHashing::compute_seed();
+// Allocate the new table, same size and hash seed
+return new G1StringDedupTable(_table->_size, _table->_hash_seed);
+}
+void G1StringDedupTable::finish_rehash(G1StringDedupTable* rehashed_table) {
+assert(rehashed_table != NULL, "Invalid table");
+// Move all newly rehashed entries into the correct buckets in the new table
+for (size_t bucket = 0; bucket < _table->_size; bucket++) {
+G1StringDedupEntry** entry = _table->bucket(bucket);
+while (*entry != NULL) {
+_table->transfer(entry, rehashed_table);
+}
+}
+rehashed_table->_entries = _table->_entries;
+// Free old table
+delete _table;
+// Install new table
+_table = rehashed_table;
+}
+void G1StringDedupTable::verify() {
+for (size_t bucket = 0; bucket < _table->_size; bucket++) {
+// Verify entries
+G1StringDedupEntry** entry = _table->bucket(bucket);
+while (*entry != NULL) {
+typeArrayOop value = (*entry)->obj();
+guarantee(value != NULL, "Object must not be NULL");
+guarantee(Universe::heap()->is_in_reserved(value), "Object must be on the heap");
+guarantee(!value->is_forwarded(), "Object must not be forwarded");
+guarantee(value->is_typeArray(), "Object must be a typeArrayOop");
+unsigned int hash = hash_code(value);
+guarantee((*entry)->hash() == hash, "Table entry has inorrect hash");
+guarantee(_table->hash_to_index(hash) == bucket, "Table entry has incorrect index");
+entry = (*entry)->next_addr();
+}
+// Verify that we do not have entries with identical oops or identical arrays.
+// We only need to compare entries in the same bucket. If the same oop or an
+// identical array has been inserted more than once into different/incorrect
+// buckets the verification step above will catch that.
+G1StringDedupEntry** entry1 = _table->bucket(bucket);
+while (*entry1 != NULL) {
+typeArrayOop value1 = (*entry1)->obj();
+G1StringDedupEntry** entry2 = (*entry1)->next_addr();
+while (*entry2 != NULL) {
+typeArrayOop value2 = (*entry2)->obj();
+guarantee(!equals(value1, value2), "Table entries must not have identical arrays");
+entry2 = (*entry2)->next_addr();
+}
+entry1 = (*entry1)->next_addr();
+}
+}
+}
+void G1StringDedupTable::trim_entry_cache() {
+MutexLockerEx ml(StringDedupTable_lock, Mutex::_no_safepoint_check_flag);
+size_t max_cache_size = (size_t)(_table->_size * _max_cache_factor);
+_entry_cache->trim(max_cache_size);
+}
+void G1StringDedupTable::print_statistics(outputStream* st) {
+st->print_cr(
+"   [Table]\n"
+"      [Memory Usage: "G1_STRDEDUP_BYTES_FORMAT_NS"]\n"
+"      [Size: "SIZE_FORMAT", Min: "SIZE_FORMAT", Max: "SIZE_FORMAT"]\n"
+"      [Entries: "UINTX_FORMAT", Load: "G1_STRDEDUP_PERCENT_FORMAT_NS", Cached: " UINTX_FORMAT ", Added: "UINTX_FORMAT", Removed: "UINTX_FORMAT"]\n"
+"      [Resize Count: "UINTX_FORMAT", Shrink Threshold: "UINTX_FORMAT"("G1_STRDEDUP_PERCENT_FORMAT_NS"), Grow Threshold: "UINTX_FORMAT"("G1_STRDEDUP_PERCENT_FORMAT_NS")]\n"
+"      [Rehash Count: "UINTX_FORMAT", Rehash Threshold: "UINTX_FORMAT", Hash Seed: 0x%x]\n"
+"      [Age Threshold: "UINTX_FORMAT"]",
+G1_STRDEDUP_BYTES_PARAM(_table->_size * sizeof(G1StringDedupEntry*) + (_table->_entries + _entry_cache->size()) * sizeof(G1StringDedupEntry)),
+_table->_size, _min_size, _max_size,
+_table->_entries, (double)_table->_entries / (double)_table->_size * 100.0, _entry_cache->size(), _entries_added, _entries_removed,
+_resize_count, _table->_shrink_threshold, _shrink_load_factor * 100.0, _table->_grow_threshold, _grow_load_factor * 100.0,
+_rehash_count, _rehash_threshold, _table->_hash_seed,
+StringDeduplicationAgeThreshold);
+}

Mercurial > jdk8-mips64-public > hotspot / file comparison

comparison: src/share/vm/gc_implementation/g1/g1StringDedupTable.cpp

src/share/vm/gc_implementation/g1/g1StringDedupTable.cpp