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.inline.hpp"
#include "classfile/stringTable.hpp"
#include "classfile/systemDictionary.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/oopStorage.inline.hpp"
#include "gc/shared/oopStorageSet.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/filemap.hpp"
#include "memory/heapShared.inline.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.hpp"
#include "oops/compressedOops.hpp"
#include "oops/oop.inline.hpp"
#include "oops/typeArrayOop.inline.hpp"
#include "oops/weakHandle.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/safepointVerifiers.hpp"
#include "runtime/timerTrace.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "services/diagnosticCommand.hpp"
#include "utilities/concurrentHashTable.inline.hpp"
#include "utilities/concurrentHashTableTasks.inline.hpp"
#include "utilities/macros.hpp"
#include "utilities/utf8.hpp"
// We prefer short chains of avg 2
const double PREF_AVG_LIST_LEN = 2.0;
// 2^24 is max size
const size_t END_SIZE = 24;
// If a chain gets to 100 something might be wrong
const size_t REHASH_LEN = 100;
// If we have as many dead items as 50% of the number of bucket
const double CLEAN_DEAD_HIGH_WATER_MARK = 0.5;
#if INCLUDE_CDS_JAVA_HEAP
inline oop read_string_from_compact_hashtable(address base_address, u4 offset) {
assert(sizeof(narrowOop) == sizeof(offset), "must be");
narrowOop v = (narrowOop)offset;
return HeapShared::decode_from_archive(v);
}
static CompactHashtable<
const jchar*, oop,
read_string_from_compact_hashtable,
java_lang_String::equals
> _shared_table;
#endif
// --------------------------------------------------------------------------
typedef ConcurrentHashTable<StringTableConfig, mtSymbol> StringTableHash;
static StringTableHash* _local_table = NULL;
volatile bool StringTable::_has_work = false;
volatile bool StringTable::_needs_rehashing = false;
volatile size_t StringTable::_uncleaned_items_count = 0;
static size_t _current_size = 0;
static volatile size_t _items_count = 0;
volatile bool _alt_hash = false;
static juint murmur_seed = 0;
uintx hash_string(const jchar* s, int len, bool useAlt) {
return useAlt ?
AltHashing::murmur3_32(murmur_seed, s, len) :
java_lang_String::hash_code(s, len);
}
class StringTableConfig : public StackObj {
private:
public:
typedef WeakHandle<vm_string_table_data> Value;
static uintx get_hash(Value const& value, bool* is_dead) {
EXCEPTION_MARK;
oop val_oop = value.peek();
if (val_oop == NULL) {
*is_dead = true;
return 0;
}
*is_dead = false;
ResourceMark rm(THREAD);
// All String oops are hashed as unicode
int length;
jchar* chars = java_lang_String::as_unicode_string(val_oop, length, THREAD);
if (chars != NULL) {
return hash_string(chars, length, _alt_hash);
}
vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "get hash from oop");
return 0;
}
// We use default allocation/deallocation but counted
static void* allocate_node(size_t size, Value const& value) {
StringTable::item_added();
return AllocateHeap(size, mtSymbol);
}
static void free_node(void* memory, Value const& value) {
value.release();
FreeHeap(memory);
StringTable::item_removed();
}
};
class StringTableLookupJchar : StackObj {
private:
Thread* _thread;
uintx _hash;
int _len;
const jchar* _str;
Handle _found;
public:
StringTableLookupJchar(Thread* thread, uintx hash, const jchar* key, int len)
: _thread(thread), _hash(hash), _len(len), _str(key) {
}
uintx get_hash() const {
return _hash;
}
bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) {
oop val_oop = value->peek();
if (val_oop == NULL) {
// dead oop, mark this hash dead for cleaning
*is_dead = true;
return false;
}
bool equals = java_lang_String::equals(val_oop, _str, _len);
if (!equals) {
return false;
}
// Need to resolve weak handle and Handleize through possible safepoint.
_found = Handle(_thread, value->resolve());
return true;
}
};
class StringTableLookupOop : public StackObj {
private:
Thread* _thread;
uintx _hash;
Handle _find;
Handle _found; // Might be a different oop with the same value that's already
// in the table, which is the point.
public:
StringTableLookupOop(Thread* thread, uintx hash, Handle handle)
: _thread(thread), _hash(hash), _find(handle) { }
uintx get_hash() const {
return _hash;
}
bool equals(WeakHandle<vm_string_table_data>* value, bool* is_dead) {
oop val_oop = value->peek();
if (val_oop == NULL) {
// dead oop, mark this hash dead for cleaning
*is_dead = true;
return false;
}
bool equals = java_lang_String::equals(_find(), val_oop);
if (!equals) {
return false;
}
// Need to resolve weak handle and Handleize through possible safepoint.
_found = Handle(_thread, value->resolve());
return true;
}
};
static size_t ceil_log2(size_t val) {
size_t ret;
for (ret = 1; ((size_t)1 << ret) < val; ++ret);
return ret;
}
void StringTable::create_table() {
size_t start_size_log_2 = ceil_log2(StringTableSize);
_current_size = ((size_t)1) << start_size_log_2;
log_trace(stringtable)("Start size: " SIZE_FORMAT " (" SIZE_FORMAT ")",
_current_size, start_size_log_2);
_local_table = new StringTableHash(start_size_log_2, END_SIZE, REHASH_LEN);
}
size_t StringTable::item_added() {
return Atomic::add(&_items_count, (size_t)1);
}
size_t StringTable::add_items_to_clean(size_t ndead) {
size_t total = Atomic::add(&_uncleaned_items_count, (size_t)ndead);
log_trace(stringtable)(
"Uncleaned items:" SIZE_FORMAT " added: " SIZE_FORMAT " total:" SIZE_FORMAT,
_uncleaned_items_count, ndead, total);
return total;
}
void StringTable::item_removed() {
Atomic::add(&_items_count, (size_t)-1);
}
double StringTable::get_load_factor() {
return (double)_items_count/_current_size;
}
double StringTable::get_dead_factor() {
return (double)_uncleaned_items_count/_current_size;
}
size_t StringTable::table_size() {
return ((size_t)1) << _local_table->get_size_log2(Thread::current());
}
void StringTable::trigger_concurrent_work() {
MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
_has_work = true;
Service_lock->notify_all();
}
// Probing
oop StringTable::lookup(Symbol* symbol) {
ResourceMark rm;
int length;
jchar* chars = symbol->as_unicode(length);
return lookup(chars, length);
}
oop StringTable::lookup(const jchar* name, int len) {
unsigned int hash = java_lang_String::hash_code(name, len);
oop string = lookup_shared(name, len, hash);
if (string != NULL) {
return string;
}
if (_alt_hash) {
hash = hash_string(name, len, true);
}
return do_lookup(name, len, hash);
}
class StringTableGet : public StackObj {
Thread* _thread;
Handle _return;
public:
StringTableGet(Thread* thread) : _thread(thread) {}
void operator()(WeakHandle<vm_string_table_data>* val) {
oop result = val->resolve();
assert(result != NULL, "Result should be reachable");
_return = Handle(_thread, result);
}
oop get_res_oop() {
return _return();
}
};
oop StringTable::do_lookup(const jchar* name, int len, uintx hash) {
Thread* thread = Thread::current();
StringTableLookupJchar lookup(thread, hash, name, len);
StringTableGet stg(thread);
bool rehash_warning;
_local_table->get(thread, lookup, stg, &rehash_warning);
update_needs_rehash(rehash_warning);
return stg.get_res_oop();
}
// Interning
oop StringTable::intern(Symbol* symbol, TRAPS) {
if (symbol == NULL) return NULL;
ResourceMark rm(THREAD);
int length;
jchar* chars = symbol->as_unicode(length);
Handle string;
oop result = intern(string, chars, length, CHECK_NULL);
return result;
}
oop StringTable::intern(oop string, TRAPS) {
if (string == NULL) return NULL;
ResourceMark rm(THREAD);
int length;
Handle h_string (THREAD, string);
jchar* chars = java_lang_String::as_unicode_string(string, length,
CHECK_NULL);
oop result = intern(h_string, chars, length, CHECK_NULL);
return result;
}
oop StringTable::intern(const char* utf8_string, TRAPS) {
if (utf8_string == NULL) return NULL;
ResourceMark rm(THREAD);
int length = UTF8::unicode_length(utf8_string);
jchar* chars = NEW_RESOURCE_ARRAY(jchar, length);
UTF8::convert_to_unicode(utf8_string, chars, length);
Handle string;
oop result = intern(string, chars, length, CHECK_NULL);
return result;
}
oop StringTable::intern(Handle string_or_null_h, const jchar* name, int len, TRAPS) {
// shared table always uses java_lang_String::hash_code
unsigned int hash = java_lang_String::hash_code(name, len);
oop found_string = lookup_shared(name, len, hash);
if (found_string != NULL) {
return found_string;
}
if (_alt_hash) {
hash = hash_string(name, len, true);
}
found_string = do_lookup(name, len, hash);
if (found_string != NULL) {
return found_string;
}
return do_intern(string_or_null_h, name, len, hash, THREAD);
}
oop StringTable::do_intern(Handle string_or_null_h, const jchar* name,
int len, uintx hash, TRAPS) {
HandleMark hm(THREAD); // cleanup strings created
Handle string_h;
if (!string_or_null_h.is_null()) {
string_h = string_or_null_h;
} else {
string_h = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
}
// Deduplicate the string before it is interned. Note that we should never
// deduplicate a string after it has been interned. Doing so will counteract
// compiler optimizations done on e.g. interned string literals.
Universe::heap()->deduplicate_string(string_h());
assert(java_lang_String::equals(string_h(), name, len),
"string must be properly initialized");
assert(len == java_lang_String::length(string_h()), "Must be same length");
StringTableLookupOop lookup(THREAD, hash, string_h);
StringTableGet stg(THREAD);
bool rehash_warning;
do {
// Callers have already looked up the String using the jchar* name, so just go to add.
WeakHandle<vm_string_table_data> wh = WeakHandle<vm_string_table_data>::create(string_h);
// The hash table takes ownership of the WeakHandle, even if it's not inserted.
if (_local_table->insert(THREAD, lookup, wh, &rehash_warning)) {
update_needs_rehash(rehash_warning);
return wh.resolve();
}
// In case another thread did a concurrent add, return value already in the table.
// This could fail if the String got gc'ed concurrently, so loop back until success.
if (_local_table->get(THREAD, lookup, stg, &rehash_warning)) {
update_needs_rehash(rehash_warning);
return stg.get_res_oop();
}
} while(true);
}
// Concurrent work
void StringTable::grow(JavaThread* jt) {
StringTableHash::GrowTask gt(_local_table);
if (!gt.prepare(jt)) {
return;
}
log_trace(stringtable)("Started to grow");
{
TraceTime timer("Grow", TRACETIME_LOG(Debug, stringtable, perf));
while (gt.do_task(jt)) {
gt.pause(jt);
{
ThreadBlockInVM tbivm(jt);
}
gt.cont(jt);
}
}
gt.done(jt);
_current_size = table_size();
log_debug(stringtable)("Grown to size:" SIZE_FORMAT, _current_size);
}
struct StringTableDoDelete : StackObj {
void operator()(WeakHandle<vm_string_table_data>* val) {
/* do nothing */
}
};
struct StringTableDeleteCheck : StackObj {
long _count;
long _item;
StringTableDeleteCheck() : _count(0), _item(0) {}
bool operator()(WeakHandle<vm_string_table_data>* val) {
++_item;
oop tmp = val->peek();
if (tmp == NULL) {
++_count;
return true;
} else {
return false;
}
}
};
void StringTable::clean_dead_entries(JavaThread* jt) {
StringTableHash::BulkDeleteTask bdt(_local_table);
if (!bdt.prepare(jt)) {
return;
}
StringTableDeleteCheck stdc;
StringTableDoDelete stdd;
{
TraceTime timer("Clean", TRACETIME_LOG(Debug, stringtable, perf));
while(bdt.do_task(jt, stdc, stdd)) {
bdt.pause(jt);
{
ThreadBlockInVM tbivm(jt);
}
bdt.cont(jt);
}
bdt.done(jt);
}
log_debug(stringtable)("Cleaned %ld of %ld", stdc._count, stdc._item);
}
void StringTable::check_concurrent_work() {
if (_has_work) {
return;
}
double load_factor = StringTable::get_load_factor();
double dead_factor = StringTable::get_dead_factor();
// We should clean/resize if we have more dead than alive,
// more items than preferred load factor or
// more dead items than water mark.
if ((dead_factor > load_factor) ||
(load_factor > PREF_AVG_LIST_LEN) ||
(dead_factor > CLEAN_DEAD_HIGH_WATER_MARK)) {
log_debug(stringtable)("Concurrent work triggered, live factor: %g dead factor: %g",
load_factor, dead_factor);
trigger_concurrent_work();
}
}
void StringTable::do_concurrent_work(JavaThread* jt) {
_has_work = false;
double load_factor = get_load_factor();
log_debug(stringtable, 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);
}
}
// Rehash
bool StringTable::do_rehash() {
if (!_local_table->is_safepoint_safe()) {
return false;
}
// We use current size, not max size.
size_t new_size = _local_table->get_size_log2(Thread::current());
StringTableHash* new_table = new StringTableHash(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 StringTable::rehash_table() {
static bool rehashed = false;
log_debug(stringtable)("Table imbalanced, rehashing called.");
// Grow instead of rehash.
if (get_load_factor() > PREF_AVG_LIST_LEN &&
!_local_table->is_max_size_reached()) {
log_debug(stringtable)("Choosing growing over rehashing.");
trigger_concurrent_work();
_needs_rehashing = false;
return;
}
// Already rehashed.
if (rehashed) {
log_warning(stringtable)("Rehashing already done, still long lists.");
trigger_concurrent_work();
_needs_rehashing = false;
return;
}
murmur_seed = AltHashing::compute_seed();
{
if (do_rehash()) {
rehashed = true;
} else {
log_info(stringtable)("Resizes in progress rehashing skipped.");
}
}
_needs_rehashing = false;
}
// Statistics
static int literal_size(oop obj) {
// NOTE: this would over-count if (pre-JDK8)
// java_lang_Class::has_offset_field() is true and the String.value array is
// shared by several Strings. However, starting from JDK8, the String.value
// array is not shared anymore.
if (obj == NULL) {
return 0;
} else if (obj->klass() == SystemDictionary::String_klass()) {
return (obj->size() + java_lang_String::value(obj)->size()) * HeapWordSize;
} else {
return obj->size();
}
}
struct SizeFunc : StackObj {
size_t operator()(WeakHandle<vm_string_table_data>* val) {
oop s = val->peek();
if (s == NULL) {
// Dead
return 0;
}
return literal_size(s);
};
};
TableStatistics StringTable::get_table_statistics() {
static TableStatistics ts;
SizeFunc sz;
ts = _local_table->statistics_get(Thread::current(), sz, ts);
return ts;
}
void StringTable::print_table_statistics(outputStream* st,
const char* table_name) {
SizeFunc sz;
_local_table->statistics_to(Thread::current(), sz, st, table_name);
}
// Verification
class VerifyStrings : StackObj {
public:
bool operator()(WeakHandle<vm_string_table_data>* val) {
oop s = val->peek();
if (s != NULL) {
assert(java_lang_String::length(s) >= 0, "Length on string must work.");
}
return true;
};
};
// This verification is part of Universe::verify() and needs to be quick.
void StringTable::verify() {
Thread* thr = Thread::current();
VerifyStrings vs;
if (!_local_table->try_scan(thr, vs)) {
log_info(stringtable)("verify unavailable at this moment");
}
}
// Verification and comp
class VerifyCompStrings : StackObj {
GrowableArray<oop>* _oops;
public:
size_t _errors;
VerifyCompStrings(GrowableArray<oop>* oops) : _oops(oops), _errors(0) {}
bool operator()(WeakHandle<vm_string_table_data>* val) {
oop s = val->resolve();
if (s == NULL) {
return true;
}
int len = _oops->length();
for (int i = 0; i < len; i++) {
bool eq = java_lang_String::equals(s, _oops->at(i));
assert(!eq, "Duplicate strings");
if (eq) {
_errors++;
}
}
_oops->push(s);
return true;
};
};
size_t StringTable::verify_and_compare_entries() {
Thread* thr = Thread::current();
GrowableArray<oop>* oops =
new (ResourceObj::C_HEAP, mtInternal)
GrowableArray<oop>((int)_current_size, true);
VerifyCompStrings vcs(oops);
if (!_local_table->try_scan(thr, vcs)) {
log_info(stringtable)("verify unavailable at this moment");
}
delete oops;
return vcs._errors;
}
// Dumping
class PrintString : StackObj {
Thread* _thr;
outputStream* _st;
public:
PrintString(Thread* thr, outputStream* st) : _thr(thr), _st(st) {}
bool operator()(WeakHandle<vm_string_table_data>* val) {
oop s = val->peek();
if (s == NULL) {
return true;
}
typeArrayOop value = java_lang_String::value_no_keepalive(s);
int length = java_lang_String::length(s);
bool is_latin1 = java_lang_String::is_latin1(s);
if (length <= 0) {
_st->print("%d: ", length);
} else {
ResourceMark rm(_thr);
int utf8_length = length;
char* utf8_string;
if (!is_latin1) {
jchar* chars = value->char_at_addr(0);
utf8_string = UNICODE::as_utf8(chars, utf8_length);
} else {
jbyte* bytes = value->byte_at_addr(0);
utf8_string = UNICODE::as_utf8(bytes, utf8_length);
}
_st->print("%d: ", utf8_length);
HashtableTextDump::put_utf8(_st, utf8_string, utf8_length);
}
_st->cr();
return true;
};
};
void StringTable::dump(outputStream* st, bool verbose) {
if (!verbose) {
print_table_statistics(st, "StringTable");
} else {
Thread* thr = Thread::current();
ResourceMark rm(thr);
st->print_cr("VERSION: 1.1");
PrintString ps(thr, st);
if (!_local_table->try_scan(thr, ps)) {
st->print_cr("dump unavailable at this moment");
}
}
}
// Utility for dumping strings
StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
DCmdWithParser(output, heap),
_verbose("-verbose", "Dump the content of each string in the table",
"BOOLEAN", false, "false") {
_dcmdparser.add_dcmd_option(&_verbose);
}
void StringtableDCmd::execute(DCmdSource source, TRAPS) {
VM_DumpHashtable dumper(output(), VM_DumpHashtable::DumpStrings,
_verbose.value());
VMThread::execute(&dumper);
}
int StringtableDCmd::num_arguments() {
ResourceMark rm;
StringtableDCmd* dcmd = new StringtableDCmd(NULL, false);
if (dcmd != NULL) {
DCmdMark mark(dcmd);
return dcmd->_dcmdparser.num_arguments();
} else {
return 0;
}
}
// Sharing
#if INCLUDE_CDS_JAVA_HEAP
oop StringTable::lookup_shared(const jchar* name, int len, unsigned int hash) {
assert(hash == java_lang_String::hash_code(name, len),
"hash must be computed using java_lang_String::hash_code");
return _shared_table.lookup(name, hash, len);
}
oop StringTable::create_archived_string(oop s, Thread* THREAD) {
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