JDK14/Java14源码在线阅读
/*
* Copyright (c) 1997, 2019, 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
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*/
#include "precompiled.hpp"
#include "classfile/altHashing.hpp"
#include "classfile/compactHashtable.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/symbolTable.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/dynamicArchive.hpp"
#include "memory/metaspaceClosure.hpp"
#include "memory/metaspaceShared.hpp"
#include "memory/resourceArea.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/timerTrace.hpp"
#include "services/diagnosticCommand.hpp"
#include "utilities/concurrentHashTable.inline.hpp"
#include "utilities/concurrentHashTableTasks.inline.hpp"
#include "utilities/utf8.hpp"
// We used to not resize at all, so let's be conservative
// and not set it too short before we decide to resize,
// to match previous startup behavior
const double PREF_AVG_LIST_LEN = 8.0;
// 2^24 is max size, like StringTable.
const size_t END_SIZE = 24;
// If a chain gets to 100 something might be wrong
const size_t REHASH_LEN = 100;
const size_t ON_STACK_BUFFER_LENGTH = 128;
// --------------------------------------------------------------------------
inline bool symbol_equals_compact_hashtable_entry(Symbol* value, const char* key, int len) {
if (value->equals(key, len)) {
assert(value->refcount() == PERM_REFCOUNT, "must be shared");
return true;
} else {
return false;
}
}
static OffsetCompactHashtable<
const char*, Symbol*,
symbol_equals_compact_hashtable_entry
> _shared_table;
static OffsetCompactHashtable<
const char*, Symbol*,
symbol_equals_compact_hashtable_entry
> _dynamic_shared_table;
// --------------------------------------------------------------------------
typedef ConcurrentHashTable<SymbolTableConfig, mtSymbol> SymbolTableHash;
static SymbolTableHash* _local_table = NULL;
volatile bool SymbolTable::_has_work = 0;
volatile bool SymbolTable::_needs_rehashing = false;
// For statistics
static size_t _symbols_removed = 0;
static size_t _symbols_counted = 0;
static size_t _current_size = 0;
static volatile size_t _items_count = 0;
static volatile bool _has_items_to_clean = false;
static volatile bool _alt_hash = false;
static volatile bool _lookup_shared_first = false;
// Static arena for symbols that are not deallocated
Arena* SymbolTable::_arena = NULL;
static juint murmur_seed = 0;
static inline void log_trace_symboltable_helper(Symbol* sym, const char* msg) {
#ifndef PRODUCT
ResourceMark rm;
log_trace(symboltable)("%s [%s]", msg, sym->as_quoted_ascii());
#endif // PRODUCT
}
// Pick hashing algorithm.
static uintx hash_symbol(const char* s, int len, bool useAlt) {
return useAlt ?
AltHashing::murmur3_32(murmur_seed, (const jbyte*)s, len) :
java_lang_String::hash_code((const jbyte*)s, len);
}
#if INCLUDE_CDS
static uintx hash_shared_symbol(const char* s, int len) {
return java_lang_String::hash_code((const jbyte*)s, len);
}
#endif
class SymbolTableConfig : public AllStatic {
private:
public:
typedef Symbol* Value; // value of the Node in the hashtable
static uintx get_hash(Value const& value, bool* is_dead) {
*is_dead = (value->refcount() == 0);
if (*is_dead) {
return 0;
} else {
return hash_symbol((const char*)value->bytes(), value->utf8_length(), _alt_hash);
}
}
// We use default allocation/deallocation but counted
static void* allocate_node(size_t size, Value const& value) {
SymbolTable::item_added();
return AllocateHeap(size, mtSymbol);
}
static void free_node(void* memory, Value const& value) {
// We get here because #1 some threads lost a race to insert a newly created Symbol
// or #2 we're cleaning up unused symbol.
// If #1, then the symbol can be either permanent (refcount==PERM_REFCOUNT),
// or regular newly created one (refcount==1)
// If #2, then the symbol is dead (refcount==0)
assert((value->refcount() == PERM_REFCOUNT) || (value->refcount() == 1) || (value->refcount() == 0),
"refcount %d", value->refcount());
if (value->refcount() == 1) {
value->decrement_refcount();
assert(value->refcount() == 0, "expected dead symbol");
}
SymbolTable::delete_symbol(value);
FreeHeap(memory);
SymbolTable::item_removed();
}
};
static size_t ceil_log2(size_t value) {
size_t ret;
for (ret = 1; ((size_t)1 << ret) < value; ++ret);
return ret;
}
void SymbolTable::create_table () {
size_t start_size_log_2 = ceil_log2(SymbolTableSize);
_current_size = ((size_t)1) << start_size_log_2;
log_trace(symboltable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
_current_size, start_size_log_2);
_local_table = new SymbolTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
// Initialize the arena for global symbols, size passed in depends on CDS.
if (symbol_alloc_arena_size == 0) {
_arena = new (mtSymbol) Arena(mtSymbol);
} else {
_arena = new (mtSymbol) Arena(mtSymbol, symbol_alloc_arena_size);
}
}
void SymbolTable::delete_symbol(Symbol* sym) {
if (sym->refcount() == PERM_REFCOUNT) {
MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena
// Deleting permanent symbol should not occur very often (insert race condition),
// so log it.
log_trace_symboltable_helper(sym, "Freeing permanent symbol");
if (!arena()->Afree(sym, sym->size())) {
log_trace_symboltable_helper(sym, "Leaked permanent symbol");
}
} else {
delete sym;
}
}
void SymbolTable::reset_has_items_to_clean() { Atomic::store(&_has_items_to_clean, false); }
void SymbolTable::mark_has_items_to_clean() { Atomic::store(&_has_items_to_clean, true); }
bool SymbolTable::has_items_to_clean() { return Atomic::load(&_has_items_to_clean); }
void SymbolTable::item_added() {
Atomic::inc(&_items_count);
}
void SymbolTable::item_removed() {
Atomic::inc(&(_symbols_removed));
Atomic::dec(&_items_count);
}
double SymbolTable::get_load_factor() {
return (double)_items_count/_current_size;
}
size_t SymbolTable::table_size() {
return ((size_t)1) << _local_table->get_size_log2(Thread::current());
}
void SymbolTable::trigger_cleanup() {
MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
_has_work = true;
Service_lock->notify_all();
}
Symbol* SymbolTable::allocate_symbol(const char* name, int len, bool c_heap) {
assert (len <= Symbol::max_length(), "should be checked by caller");
Symbol* sym;
if (Arguments::is_dumping_archive()) {
c_heap = false;
}
if (c_heap) {
// refcount starts as 1
sym = new (len) Symbol((const u1*)name, len, 1);
assert(sym != NULL, "new should call vm_exit_out_of_memory if C_HEAP is exhausted");
} else {
// Allocate to global arena
MutexLocker ml(SymbolArena_lock, Mutex::_no_safepoint_check_flag); // Protect arena
sym = new (len, arena()) Symbol((const u1*)name, len, PERM_REFCOUNT);
}
return sym;
}
class SymbolsDo : StackObj {
SymbolClosure *_cl;
public:
SymbolsDo(SymbolClosure *cl) : _cl(cl) {}
bool operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
_cl->do_symbol(value);
return true;
};
};
class SharedSymbolIterator {
SymbolClosure* _symbol_closure;
public:
SharedSymbolIterator(SymbolClosure* f) : _symbol_closure(f) {}
void do_value(Symbol* symbol) {
_symbol_closure->do_symbol(&symbol);
}
};
// Call function for all symbols in the symbol table.
void SymbolTable::symbols_do(SymbolClosure *cl) {
// all symbols from shared table
SharedSymbolIterator iter(cl);
_shared_table.iterate(&iter);
_dynamic_shared_table.iterate(&iter);
// all symbols from the dynamic table
SymbolsDo sd(cl);
if (!_local_table->try_scan(Thread::current(), sd)) {
log_info(symboltable)("symbols_do unavailable at this moment");
}
}
class MetaspacePointersDo : StackObj {
MetaspaceClosure *_it;
public:
MetaspacePointersDo(MetaspaceClosure *it) : _it(it) {}
bool operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
_it->push(value);
return true;
};
};
void SymbolTable::metaspace_pointers_do(MetaspaceClosure* it) {
Arguments::assert_is_dumping_archive();
MetaspacePointersDo mpd(it);
_local_table->do_safepoint_scan(mpd);
}
Symbol* SymbolTable::lookup_dynamic(const char* name,
int len, unsigned int hash) {
Symbol* sym = do_lookup(name, len, hash);
assert((sym == NULL) || sym->refcount() != 0, "refcount must not be zero");
return sym;
}
#if INCLUDE_CDS
Symbol* SymbolTable::lookup_shared(const char* name,
int len, unsigned int hash) {
Symbol* sym = NULL;
if (!_shared_table.empty()) {
if (_alt_hash) {
// hash_code parameter may use alternate hashing algorithm but the shared table
// always uses the same original hash code.
hash = hash_shared_symbol(name, len);
}
sym = _shared_table.lookup(name, hash, len);
if (sym == NULL && DynamicArchive::is_mapped()) {
sym = _dynamic_shared_table.lookup(name, hash, len);
}
}
return sym;
}
#endif
Symbol* SymbolTable::lookup_common(const char* name,
int len, unsigned int hash) {
Symbol* sym;
if (_lookup_shared_first) {
sym = lookup_shared(name, len, hash);
if (sym == NULL) {
_lookup_shared_first = false;
sym = lookup_dynamic(name, len, hash);
}
} else {
sym = lookup_dynamic(name, len, hash);
if (sym == NULL) {
sym = lookup_shared(name, len, hash);
if (sym != NULL) {
_lookup_shared_first = true;
}
}
}
return sym;
}
Symbol* SymbolTable::new_symbol(const char* name, int len) {
unsigned int hash = hash_symbol(name, len, _alt_hash);
Symbol* sym = lookup_common(name, len, hash);
if (sym == NULL) {
sym = do_add_if_needed(name, len, hash, true);
}
assert(sym->refcount() != 0, "lookup should have incremented the count");
assert(sym->equals(name, len), "symbol must be properly initialized");
return sym;
}
Symbol* SymbolTable::new_symbol(const Symbol* sym, int begin, int end) {
assert(begin <= end && end <= sym->utf8_length(), "just checking");
assert(sym->refcount() != 0, "require a valid symbol");
const char* name = (const char*)sym->base() + begin;
int len = end - begin;
unsigned int hash = hash_symbol(name, len, _alt_hash);
Symbol* found = lookup_common(name, len, hash);
if (found == NULL) {
found = do_add_if_needed(name, len, hash, true);
}
return found;
}
class SymbolTableLookup : StackObj {
private:
Thread* _thread;
uintx _hash;
int _len;
const char* _str;
public:
SymbolTableLookup(const char* key, int len, uintx hash)
: _hash(hash), _len(len), _str(key) {}
uintx get_hash() const {
return _hash;
}
bool equals(Symbol** value, bool* is_dead) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
Symbol *sym = *value;
if (sym->equals(_str, _len)) {
if (sym->try_increment_refcount()) {
// something is referencing this symbol now.
return true;
} else {
assert(sym->refcount() == 0, "expected dead symbol");
*is_dead = true;
return false;
}
} else {
*is_dead = (sym->refcount() == 0);
return false;
}
}
};
class SymbolTableGet : public StackObj {
Symbol* _return;
public:
SymbolTableGet() : _return(NULL) {}
void operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
_return = *value;
}
Symbol* get_res_sym() const {
return _return;
}
};
Symbol* SymbolTable::do_lookup(const char* name, int len, uintx hash) {
Thread* thread = Thread::current();
SymbolTableLookup lookup(name, len, hash);
SymbolTableGet stg;
bool rehash_warning = false;
_local_table->get(thread, lookup, stg, &rehash_warning);
update_needs_rehash(rehash_warning);
Symbol* sym = stg.get_res_sym();
assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
return sym;
}
Symbol* SymbolTable::lookup_only(const char* name, int len, unsigned int& hash) {
hash = hash_symbol(name, len, _alt_hash);
return lookup_common(name, len, hash);
}
// Suggestion: Push unicode-based lookup all the way into the hashing
// and probing logic, so there is no need for convert_to_utf8 until
// an actual new Symbol* is created.
Symbol* SymbolTable::new_symbol(const jchar* name, int utf16_length) {
int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
char stack_buf[ON_STACK_BUFFER_LENGTH];
if (utf8_length < (int) sizeof(stack_buf)) {
char* chars = stack_buf;
UNICODE::convert_to_utf8(name, utf16_length, chars);
return new_symbol(chars, utf8_length);
} else {
ResourceMark rm;
char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
UNICODE::convert_to_utf8(name, utf16_length, chars);
return new_symbol(chars, utf8_length);
}
}
Symbol* SymbolTable::lookup_only_unicode(const jchar* name, int utf16_length,
unsigned int& hash) {
int utf8_length = UNICODE::utf8_length((jchar*) name, utf16_length);
char stack_buf[ON_STACK_BUFFER_LENGTH];
if (utf8_length < (int) sizeof(stack_buf)) {
char* chars = stack_buf;
UNICODE::convert_to_utf8(name, utf16_length, chars);
return lookup_only(chars, utf8_length, hash);
} else {
ResourceMark rm;
char* chars = NEW_RESOURCE_ARRAY(char, utf8_length + 1);
UNICODE::convert_to_utf8(name, utf16_length, chars);
return lookup_only(chars, utf8_length, hash);
}
}
void SymbolTable::new_symbols(ClassLoaderData* loader_data, const constantPoolHandle& cp,
int names_count, const char** names, int* lengths,
int* cp_indices, unsigned int* hashValues) {
bool c_heap = !loader_data->is_the_null_class_loader_data();
for (int i = 0; i < names_count; i++) {
const char *name = names[i];
int len = lengths[i];
unsigned int hash = hashValues[i];
assert(lookup_shared(name, len, hash) == NULL, "must have checked already");
Symbol* sym = do_add_if_needed(name, len, hash, c_heap);
assert(sym->refcount() != 0, "lookup should have incremented the count");
cp->symbol_at_put(cp_indices[i], sym);
}
}
Symbol* SymbolTable::do_add_if_needed(const char* name, int len, uintx hash, bool heap) {
SymbolTableLookup lookup(name, len, hash);
SymbolTableGet stg;
bool clean_hint = false;
bool rehash_warning = false;
Symbol* sym = NULL;
Thread* THREAD = Thread::current();
do {
// Callers have looked up the symbol once, insert the symbol.
sym = allocate_symbol(name, len, heap);
if (_local_table->insert(THREAD, lookup, sym, &rehash_warning, &clean_hint)) {
break;
}
// In case another thread did a concurrent add, return value already in the table.
// This could fail if the symbol got deleted concurrently, so loop back until success.
if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) {
sym = stg.get_res_sym();
break;
}
} while(true);
update_needs_rehash(rehash_warning);
if (clean_hint) {
mark_has_items_to_clean();
check_concurrent_work();
}
assert((sym == NULL) || sym->refcount() != 0, "found dead symbol");
return sym;
}
Symbol* SymbolTable::new_permanent_symbol(const char* name) {
unsigned int hash = 0;
int len = (int)strlen(name);
Symbol* sym = SymbolTable::lookup_only(name, len, hash);
if (sym == NULL) {
sym = do_add_if_needed(name, len, hash, false);
}
if (!sym->is_permanent()) {
sym->make_permanent();
log_trace_symboltable_helper(sym, "Asked for a permanent symbol, but got a regular one");
}
return sym;
}
struct SizeFunc : StackObj {
size_t operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
return (*value)->size() * HeapWordSize;
};
};
TableStatistics SymbolTable::get_table_statistics() {
static TableStatistics ts;
SizeFunc sz;
ts = _local_table->statistics_get(Thread::current(), sz, ts);
return ts;
}
void SymbolTable::print_table_statistics(outputStream* st,
const char* table_name) {
SizeFunc sz;
_local_table->statistics_to(Thread::current(), sz, st, table_name);
}
// Verification
class VerifySymbols : StackObj {
public:
bool operator()(Symbol** value) {
guarantee(value != NULL, "expected valid value");
guarantee(*value != NULL, "value should point to a symbol");
Symbol* sym = *value;
guarantee(sym->equals((const char*)sym->bytes(), sym->utf8_length()),
"symbol must be internally consistent");
return true;
};
};
void SymbolTable::verify() {
Thread* thr = Thread::current();
VerifySymbols vs;
if (!_local_table->try_scan(thr, vs)) {
log_info(symboltable)("verify unavailable at this moment");
}
}
// Dumping
class DumpSymbol : StackObj {
Thread* _thr;
outputStream* _st;
public:
DumpSymbol(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
bool operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
Symbol* sym = *value;
const char* utf8_string = (const char*)sym->bytes();
int utf8_length = sym->utf8_length();
_st->print("%d %d: ", utf8_length, sym->refcount());
HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
_st->cr();
return true;
};
};
void SymbolTable::dump(outputStream* st, bool verbose) {
if (!verbose) {
print_table_statistics(st, "SymbolTable");
} else {
Thread* thr = Thread::current();
ResourceMark rm(thr);
st->print_cr("VERSION: 1.1");
DumpSymbol ds(thr, st);
if (!_local_table->try_scan(thr, ds)) {
log_info(symboltable)("dump unavailable at this moment");
}
}
}
#if INCLUDE_CDS
struct CopyToArchive : StackObj {
CompactHashtableWriter* _writer;
CopyToArchive(CompactHashtableWriter* writer) : _writer(writer) {}
bool operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
Symbol* sym = *value;
unsigned int fixed_hash = hash_shared_symbol((const char*)sym->bytes(), sym->utf8_length());
assert(fixed_hash == hash_symbol((const char*)sym->bytes(), sym->utf8_length(), false),
"must not rehash during dumping");
if (DynamicDumpSharedSpaces) {
sym = DynamicArchive::original_to_target(sym);
}
_writer->add(fixed_hash, MetaspaceShared::object_delta_u4(sym));
return true;
}
};
void SymbolTable::copy_shared_symbol_table(CompactHashtableWriter* writer) {
CopyToArchive copy(writer);
_local_table->do_safepoint_scan(copy);
}
size_t SymbolTable::estimate_size_for_archive() {
return CompactHashtableWriter::estimate_size(int(_items_count));
}
void SymbolTable::write_to_archive(bool is_static_archive) {
CompactHashtableWriter writer(int(_items_count),
&MetaspaceShared::stats()->symbol);
copy_shared_symbol_table(&writer);
if (is_static_archive) {
_shared_table.reset();
writer.dump(&_shared_table, "symbol");
// Verify table is correct
Symbol* sym = vmSymbols::java_lang_Object();
const char* name = (const char*)sym->bytes();
int len = sym->utf8_length();
unsigned int hash = hash_symbol(name, len, _alt_hash);
assert(sym == _shared_table.lookup(name, hash, len), "sanity");
} else {
_dynamic_shared_table.reset();
writer.dump(&_dynamic_shared_table, "symbol");
}
}
void SymbolTable::serialize_shared_table_header(SerializeClosure* soc,
bool is_static_archive) {
OffsetCompactHashtable<const char*, Symbol*, symbol_equals_compact_hashtable_entry> * table;
if (is_static_archive) {
table = &_shared_table;
} else {
table = &_dynamic_shared_table;
}
table->serialize_header(soc);
if (soc->writing()) {
// Sanity. Make sure we don't use the shared table at dump time
table->reset();
}
}
#endif //INCLUDE_CDS
// Concurrent work
void SymbolTable::grow(JavaThread* jt) {
SymbolTableHash::GrowTask gt(_local_table);
if (!gt.prepare(jt)) {
return;
}
log_trace(symboltable)("Started to grow");
{
TraceTime timer("Grow", TRACETIME_LOG(Debug, symboltable, perf));
while (gt.do_task(jt)) {
gt.pause(jt);
{
ThreadBlockInVM tbivm(jt);
}
gt.cont(jt);
}
}
gt.done(jt);
_current_size = table_size();
log_debug(symboltable)("Grown to size:" SIZE_FORMAT, _current_size);
}
struct SymbolTableDoDelete : StackObj {
size_t _deleted;
SymbolTableDoDelete() : _deleted(0) {}
void operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
Symbol *sym = *value;
assert(sym->refcount() == 0, "refcount");
_deleted++;
}
};
struct SymbolTableDeleteCheck : StackObj {
size_t _processed;
SymbolTableDeleteCheck() : _processed(0) {}
bool operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
assert(*value != NULL, "value should point to a symbol");
_processed++;
Symbol *sym = *value;
return (sym->refcount() == 0);
}
};
void SymbolTable::clean_dead_entries(JavaThread* jt) {
SymbolTableHash::BulkDeleteTask bdt(_local_table);
if (!bdt.prepare(jt)) {
return;
}
SymbolTableDeleteCheck stdc;
SymbolTableDoDelete stdd;
{
TraceTime timer("Clean", TRACETIME_LOG(Debug, symboltable, perf));
while (bdt.do_task(jt, stdc, stdd)) {
bdt.pause(jt);
{
ThreadBlockInVM tbivm(jt);
}
bdt.cont(jt);
}
reset_has_items_to_clean();
bdt.done(jt);
}
Atomic::add(&_symbols_counted, stdc._processed);
log_debug(symboltable)("Cleaned " SIZE_FORMAT " of " SIZE_FORMAT,
stdd._deleted, stdc._processed);
}
void SymbolTable::check_concurrent_work() {
if (_has_work) {
return;
}
// We should clean/resize if we have
// more items than preferred load factor or
// more dead items than water mark.
if (has_items_to_clean() || (get_load_factor() > PREF_AVG_LIST_LEN)) {
log_debug(symboltable)("Concurrent work triggered, load factor: %f, items to clean: %s",
get_load_factor(), has_items_to_clean() ? "true" : "false");
trigger_cleanup();
}
}
void SymbolTable::do_concurrent_work(JavaThread* jt) {
double load_factor = get_load_factor();
log_debug(symboltable, perf)("Concurrent work, live factor: %g", load_factor);
// We prefer growing, since that also removes dead items
if (load_factor > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
grow(jt);
} else {
clean_dead_entries(jt);
}
_has_work = false;
}
// Rehash
bool SymbolTable::do_rehash() {
if (!_local_table->is_safepoint_safe()) {
return false;
}
// We use current size
size_t new_size = _local_table->get_size_log2(Thread::current());
SymbolTableHash* new_table = new SymbolTableHash(new_size, END_SIZE, REHASH_LEN);
// Use alt hash from now on
_alt_hash = true;
if (!_local_table->try_move_nodes_to(Thread::current(), new_table)) {
_alt_hash = false;
delete new_table;
return false;
}
// free old table
delete _local_table;
_local_table = new_table;
return true;
}
void SymbolTable::rehash_table() {
static bool rehashed = false;
log_debug(symboltable)("Table imbalanced, rehashing called.");
// Grow instead of rehash.
if (get_load_factor() > PREF_AVG_LIST_LEN &&
!_local_table->is_max_size_reached()) {
log_debug(symboltable)("Choosing growing over rehashing.");
trigger_cleanup();
_needs_rehashing = false;
return;
}
// Already rehashed.
if (rehashed) {
log_warning(symboltable)("Rehashing already done, still long lists.");
trigger_cleanup();
_needs_rehashing = false;
return;
}
murmur_seed = AltHashing::compute_seed();
if (do_rehash()) {
rehashed = true;
} else {
log_info(symboltable)("Resizes in progress rehashing skipped.");
}
_needs_rehashing = false;
}
//---------------------------------------------------------------------------
// Non-product code
#ifndef PRODUCT
class HistogramIterator : StackObj {
public:
static const size_t results_length = 100;
size_t counts[results_length];
size_t sizes[results_length];
size_t total_size;
size_t total_count;
size_t total_length;
size_t max_length;
size_t out_of_range_count;
size_t out_of_range_size;
HistogramIterator() : total_size(0), total_count(0), total_length(0),
max_length(0), out_of_range_count(0), out_of_range_size(0) {
// initialize results to zero
for (size_t i = 0; i < results_length; i++) {
counts[i] = 0;
sizes[i] = 0;
}
}
bool operator()(Symbol** value) {
assert(value != NULL, "expected valid value");
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