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src/hotspot/share/classfile/stringTable.cpp
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rev 50285 : 8195097: Make it possible to process StringTable outside safepoint
Reviewed-by:
rev 50286 : [mq]: 8195097-stringtable-robbin
@@ -27,255 +27,305 @@
#include "classfile/compactHashtable.inline.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/oopStorageParState.inline.hpp"
#include "logging/log.hpp"
+#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/filemap.hpp"
#include "memory/metaspaceShared.hpp"
#include "memory/resourceArea.hpp"
#include "memory/universe.hpp"
#include "oops/access.inline.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/hashtable.inline.hpp"
+#include "utilities/concurrentHashTable.inline.hpp"
+#include "utilities/concurrentHashTableTasks.inline.hpp"
#include "utilities/macros.hpp"
-// the number of buckets a thread claims
-const int ClaimChunkSize = 32;
-
-#ifdef ASSERT
-class StableMemoryChecker : public StackObj {
- enum { _bufsize = wordSize*4 };
-
- address _region;
- jint _size;
- u1 _save_buf[_bufsize];
-
- int sample(u1* save_buf) {
- if (_size <= _bufsize) {
- memcpy(save_buf, _region, _size);
- return _size;
- } else {
- // copy head and tail
- memcpy(&save_buf[0], _region, _bufsize/2);
- memcpy(&save_buf[_bufsize/2], _region + _size - _bufsize/2, _bufsize/2);
- return (_bufsize/2)*2;
- }
- }
-
- public:
- StableMemoryChecker(const void* region, jint size) {
- _region = (address) region;
- _size = size;
- sample(_save_buf);
- }
-
- bool verify() {
- u1 check_buf[sizeof(_save_buf)];
- int check_size = sample(check_buf);
- return (0 == memcmp(_save_buf, check_buf, check_size));
- }
-
- void set_region(const void* region) { _region = (address) region; }
-};
-#endif
-
+// We prefer short chains of avg 2
+#define PREF_AVG_LIST_LEN 2
+// We start with same old size, consider to reduce this
+#define START_SIZE 16
+// 2^24 is max size
+#define END_SIZE 24
+// If a chain gets to 32 something might be wrong
+#define REHASH_LEN 32
+// If we have as many dead items as 50% of the number of bucket
+#define CLEAN_DEAD_HIGH_WATER_MARK 0.5
// --------------------------------------------------------------------------
StringTable* StringTable::_the_table = NULL;
bool StringTable::_shared_string_mapped = false;
-bool StringTable::_needs_rehashing = false;
-
-volatile int StringTable::_parallel_claimed_idx = 0;
-
CompactHashtable<oop, char> StringTable::_shared_table;
+bool StringTable::_alt_hash = false;
-// Pick hashing algorithm
-unsigned int StringTable::hash_string(const jchar* s, int len) {
- return use_alternate_hashcode() ? alt_hash_string(s, len) :
- java_lang_String::hash_code(s, len);
-}
+static juint murmur_seed = 0;
-unsigned int StringTable::alt_hash_string(const jchar* s, int len) {
- return AltHashing::murmur3_32(seed(), s, len);
+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);
}
-unsigned int StringTable::hash_string(oop string) {
+class StringTableConfig : public StringTableHash::BaseConfig {
+ private:
+ public:
+ static uintx get_hash(WeakHandle<vm_string_table_data> const& value,
+ bool* is_dead) {
EXCEPTION_MARK;
- if (string == NULL) {
- return hash_string((jchar*)NULL, 0);
+ 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(string, length, THREAD);
+ jchar* chars = java_lang_String::as_unicode_string(val_oop, length, THREAD);
if (chars != NULL) {
- return hash_string(chars, length);
- } else {
- vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "unable to create Unicode string for verification");
+ return hash_string(chars, length, StringTable::_alt_hash);
+ }
+ vm_exit_out_of_memory(length, OOM_MALLOC_ERROR, "get hash from oop");
return 0;
}
-}
-
-oop StringTable::string_object(HashtableEntry<oop, mtSymbol>* entry) {
- return RootAccess<ON_PHANTOM_OOP_REF>::oop_load(entry->literal_addr());
-}
-
-oop StringTable::string_object_no_keepalive(HashtableEntry<oop, mtSymbol>* entry) {
- // The AS_NO_KEEPALIVE peeks at the oop without keeping it alive.
- // This is *very dangerous* in general but is okay in this specific
- // case. The subsequent oop_load keeps the oop alive if it it matched
- // the jchar* string.
- return RootAccess<ON_PHANTOM_OOP_REF | AS_NO_KEEPALIVE>::oop_load(entry->literal_addr());
-}
-
-void StringTable::set_string_object(HashtableEntry<oop, mtSymbol>* entry, oop string) {
- RootAccess<ON_PHANTOM_OOP_REF>::oop_store(entry->literal_addr(), string);
-}
+ // We use default allocation/deallocation but counted
+ static void* allocate_node(size_t size,
+ WeakHandle<vm_string_table_data> const& value) {
+ StringTable::item_added();
+ return StringTableHash::BaseConfig::allocate_node(size, value);
+ }
+ static void free_node(void* memory,
+ WeakHandle<vm_string_table_data> const& value) {
+ value.release();
+ StringTableHash::BaseConfig::free_node(memory, value);
+ StringTable::item_removed();
+ }
+};
-oop StringTable::lookup_shared(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((const char*)name, hash, len);
-}
+class StringTableLookupJchar {
+ private:
+ Thread* _thread;
+ uintx _hash;
+ int _len;
+ const jchar* _str;
+ Handle _found;
-oop StringTable::lookup_in_main_table(int index, jchar* name,
- int len, unsigned int hash) {
- int count = 0;
- for (HashtableEntry<oop, mtSymbol>* l = bucket(index); l != NULL; l = l->next()) {
- count++;
- if (l->hash() == hash) {
- if (java_lang_String::equals(string_object_no_keepalive(l), name, len)) {
- // We must perform a new load with string_object() that keeps the string
- // alive as we must expose the oop as strongly reachable when exiting
- // this context, in case the oop gets published.
- return string_object(l);
+ public:
+ StringTableLookupJchar(Thread* thread, uintx hash, const jchar* key, int len)
+ : _thread(thread), _hash(hash), _str(key), _len(len) {
}
+ 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, (jchar*)_str, _len);
+ if (!equals) {
+ return false;
}
- // If the bucket size is too deep check if this hash code is insufficient.
- if (count >= rehash_count && !needs_rehashing()) {
- _needs_rehashing = check_rehash_table(count);
+ // Need to resolve weak handle and Handleize through possible safepoint.
+ _found = Handle(_thread, value->resolve());
+ return true;
}
- return NULL;
-}
-
+};
-oop StringTable::basic_add(int index_arg, Handle string, jchar* name,
- int len, unsigned int hashValue_arg, TRAPS) {
+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) { }
- assert(java_lang_String::equals(string(), name, len),
- "string must be properly initialized");
- // Cannot hit a safepoint in this function because the "this" pointer can move.
- NoSafepointVerifier nsv;
+ uintx get_hash() const {
+ return _hash;
+ }
- // Check if the symbol table has been rehashed, if so, need to recalculate
- // the hash value and index before second lookup.
- unsigned int hashValue;
- int index;
- if (use_alternate_hashcode()) {
- hashValue = alt_hash_string(name, len);
- index = hash_to_index(hashValue);
- } else {
- hashValue = hashValue_arg;
- index = index_arg;
+ 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;
}
+};
- // Since look-up was done lock-free, we need to check if another
- // thread beat us in the race to insert the symbol.
+StringTable::StringTable() : _local_table(NULL), _current_size(0), _has_work(0),
+ _needs_rehashing(false), _weak_handles(NULL), _items(0), _uncleaned_items(0) {
+ _weak_handles = new OopStorage("StringTable weak",
+ StringTableWeakAlloc_lock,
+ StringTableWeakActive_lock);
+ _local_table = new StringTableHash(START_SIZE, END_SIZE, REHASH_LEN);
+ _current_size = ((size_t)1) << START_SIZE;
+}
- // No need to lookup the shared table from here since the caller (intern()) already did
- oop test = lookup_in_main_table(index, name, len, hashValue); // calls lookup(u1*, int)
- if (test != NULL) {
- // Entry already added
- return test;
- }
+size_t StringTable::item_added() {
+ return Atomic::add((size_t)1, &(the_table()->_items));
+}
- HashtableEntry<oop, mtSymbol>* entry = new_entry(hashValue, string());
- add_entry(index, entry);
- return string();
+size_t StringTable::items_to_clean(size_t ncl) {
+ size_t total = Atomic::add((size_t)ncl, &(the_table()->_uncleaned_items));
+ log_trace(stringtable)(
+ "Uncleaned items:" SIZE_FORMAT " added: " SIZE_FORMAT " total:" SIZE_FORMAT,
+ the_table()->_uncleaned_items, ncl, total);
+ return total;
}
+void StringTable::item_removed() {
+ Atomic::add((size_t)-1, &(the_table()->_items));
+ Atomic::add((size_t)-1, &(the_table()->_uncleaned_items));
+}
+
+double StringTable::get_load_factor() {
+ return (_items*1.0)/_current_size;
+}
+
+double StringTable::get_dead_factor() {
+ return (_uncleaned_items*1.0)/_current_size;
+}
oop StringTable::lookup(Symbol* symbol) {
ResourceMark rm;
int length;
jchar* chars = symbol->as_unicode(length);
return lookup(chars, length);
}
oop StringTable::lookup(jchar* name, int len) {
- // shared table always uses java_lang_String::hash_code
unsigned int hash = java_lang_String::hash_code(name, len);
- oop string = lookup_shared(name, len, hash);
+ oop string = StringTable::the_table()->lookup_shared(name, len, hash);
if (string != NULL) {
return string;
}
- if (use_alternate_hashcode()) {
- hash = alt_hash_string(name, len);
+ if (StringTable::_alt_hash) {
+ hash = hash_string(name, len, true);
}
- int index = the_table()->hash_to_index(hash);
- string = the_table()->lookup_in_main_table(index, name, len, hash);
-
- return string;
+ return StringTable::the_table()->do_lookup( name, len, hash);
}
-oop StringTable::intern(Handle string_or_null, jchar* name,
- int len, TRAPS) {
- // shared table always uses java_lang_String::hash_code
- unsigned int hashValue = java_lang_String::hash_code(name, len);
- oop found_string = lookup_shared(name, len, hashValue);
- if (found_string != NULL) {
- return found_string;
+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);
}
- if (use_alternate_hashcode()) {
- hashValue = alt_hash_string(name, len);
+ oop get_res_oop() {
+ return _return();
}
- int index = the_table()->hash_to_index(hashValue);
- found_string = the_table()->lookup_in_main_table(index, name, len, hashValue);
+};
+
+oop StringTable::do_lookup(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);
+ if (rehash_warning) {
+ _needs_rehashing = true;
+ }
+ return stg.get_res_oop();
+}
+
+class StringTableCreateEntry : public StackObj {
+ private:
+ Thread* _thread;
+ Handle _return;
+ Handle _store;
+ public:
+ StringTableCreateEntry(Thread* thread, Handle store)
+ : _thread(thread), _store(store) {}
- // Found
+ WeakHandle<vm_string_table_data> operator()() { // No dups found
+ WeakHandle<vm_string_table_data> wh =
+ WeakHandle<vm_string_table_data>::create(_store);
+ return wh;
+ }
+ void operator()(bool inserted, WeakHandle<vm_string_table_data>* val) {
+ oop result = val->resolve();
+ assert(result != NULL, "Result should be reachable");
+ _return = Handle(_thread, result);
+ }
+ oop get_return() const {
+ return _return();
+ }
+};
+
+oop StringTable::intern(Handle string_or_null_h, 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 = StringTable::the_table()->lookup_shared(name, len, hash);
if (found_string != NULL) {
return found_string;
}
+ if (StringTable::_alt_hash) {
+ hash = hash_string(name, len, true);
+ }
+ return StringTable::the_table()->do_intern(string_or_null_h, name, len,
+ hash, CHECK_NULL);
+}
- debug_only(StableMemoryChecker smc(name, len * sizeof(name[0])));
- assert(!Universe::heap()->is_in_reserved(name),
- "proposed name of symbol must be stable");
-
+oop StringTable::do_intern(Handle string_or_null_h, jchar* name,
+ int len, uintx hash, TRAPS) {
HandleMark hm(THREAD); // cleanup strings created
- Handle string;
- // try to reuse the string if possible
- if (!string_or_null.is_null()) {
- string = string_or_null;
+ Handle string_h;
+
+ if (!string_or_null_h.is_null()) {
+ string_h = string_or_null_h;
} else {
- string = java_lang_String::create_from_unicode(name, len, CHECK_NULL);
+ 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());
+ Universe::heap()->deduplicate_string(string_h());
- // Grab the StringTable_lock before getting the_table() because it could
- // change at safepoint.
- oop added_or_found;
- {
- MutexLocker ml(StringTable_lock, THREAD);
- // Otherwise, add to symbol to table
- added_or_found = the_table()->basic_add(index, string, name, len,
- hashValue, CHECK_NULL);
+ 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);
+ StringTableCreateEntry stc(THREAD, string_h);
+
+ bool rehash_warning;
+ _local_table->get_insert_lazy(THREAD, lookup, stc, stc, &rehash_warning);
+ if (rehash_warning) {
+ _needs_rehashing = true;
}
-
- return added_or_found;
+ return stc.get_return();
}
oop StringTable::intern(Symbol* symbol, TRAPS) {
if (symbol == NULL) return NULL;
ResourceMark rm(THREAD);
@@ -284,23 +334,21 @@
Handle string;
oop result = intern(string, chars, length, CHECK_NULL);
return result;
}
-
-oop StringTable::intern(oop string, TRAPS)
-{
+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);
+ 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);
@@ -308,344 +356,358 @@
Handle string;
oop result = intern(string, chars, length, CHECK_NULL);
return result;
}
-void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
- BucketUnlinkContext context;
- buckets_unlink_or_oops_do(is_alive, f, 0, the_table()->table_size(), &context);
- _the_table->bulk_free_entries(&context);
- *processed = context._num_processed;
- *removed = context._num_removed;
-}
-
-void StringTable::possibly_parallel_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int* processed, int* removed) {
- // Readers of the table are unlocked, so we should only be removing
- // entries at a safepoint.
- assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
- const int limit = the_table()->table_size();
-
- BucketUnlinkContext context;
- for (;;) {
- // Grab next set of buckets to scan
- int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
- if (start_idx >= limit) {
- // End of table
- break;
- }
-
- int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
- buckets_unlink_or_oops_do(is_alive, f, start_idx, end_idx, &context);
- }
- _the_table->bulk_free_entries(&context);
- *processed = context._num_processed;
- *removed = context._num_removed;
+size_t StringTable::table_size(Thread* thread) {
+ return ((size_t)(1)) << _local_table->get_size_log2(thread != NULL ? thread
+ : Thread::current());
}
-void StringTable::buckets_oops_do(OopClosure* f, int start_idx, int end_idx) {
- const int limit = the_table()->table_size();
-
- assert(0 <= start_idx && start_idx <= limit,
- "start_idx (%d) is out of bounds", start_idx);
- assert(0 <= end_idx && end_idx <= limit,
- "end_idx (%d) is out of bounds", end_idx);
- assert(start_idx <= end_idx,
- "Index ordering: start_idx=%d, end_idx=%d",
- start_idx, end_idx);
-
- for (int i = start_idx; i < end_idx; i += 1) {
- HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
- while (entry != NULL) {
- assert(!entry->is_shared(), "CDS not used for the StringTable");
-
- f->do_oop((oop*)entry->literal_addr());
-
- entry = entry->next();
+class StringTableIsAliveCounter : public BoolObjectClosure {
+ BoolObjectClosure* _real_boc;
+ public:
+ size_t _count;
+ size_t _count_total;
+ StringTableIsAliveCounter(BoolObjectClosure* boc) : _real_boc(boc), _count(0),
+ _count_total(0) {}
+ bool do_object_b(oop obj) {
+ bool ret = _real_boc->do_object_b(obj);
+ if (!ret) {
+ ++_count;
}
+ ++_count_total;
+ return ret;
}
-}
-
-void StringTable::buckets_unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f, int start_idx, int end_idx, BucketUnlinkContext* context) {
- const int limit = the_table()->table_size();
-
- assert(0 <= start_idx && start_idx <= limit,
- "start_idx (%d) is out of bounds", start_idx);
- assert(0 <= end_idx && end_idx <= limit,
- "end_idx (%d) is out of bounds", end_idx);
- assert(start_idx <= end_idx,
- "Index ordering: start_idx=%d, end_idx=%d",
- start_idx, end_idx);
-
- for (int i = start_idx; i < end_idx; ++i) {
- HashtableEntry<oop, mtSymbol>** p = the_table()->bucket_addr(i);
- HashtableEntry<oop, mtSymbol>* entry = the_table()->bucket(i);
- while (entry != NULL) {
- assert(!entry->is_shared(), "CDS not used for the StringTable");
+};
- if (is_alive->do_object_b(string_object_no_keepalive(entry))) {
- if (f != NULL) {
- f->do_oop(entry->literal_addr());
- }
- p = entry->next_addr();
- } else {
- *p = entry->next();
- context->free_entry(entry);
- }
- context->_num_processed++;
- entry = *p;
+void StringTable::trigger_concurrent_work() {
+ MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
+ the_table()->_has_work = true;
+ Service_lock->notify_all();
+}
+
+void StringTable::unlink_or_oops_do(BoolObjectClosure* is_alive, OopClosure* f,
+ int* processed, int* removed) {
+ DoNothingClosure dnc;
+ assert(is_alive != NULL, "No closure");
+ StringTableIsAliveCounter stiac(is_alive);
+ OopClosure* tmp = f != NULL ? f : &dnc;
+
+ StringTable::the_table()->_weak_handles->weak_oops_do(&stiac, tmp);
+
+ StringTable::the_table()->items_to_clean(stiac._count);
+ StringTable::the_table()->check_concurrent_work();
+ if (processed != NULL) {
+ *processed = (int) stiac._count_total;
}
+ if (removed != NULL) {
+ *removed = (int) stiac._count;
}
}
void StringTable::oops_do(OopClosure* f) {
- buckets_oops_do(f, 0, the_table()->table_size());
+ assert(f != NULL, "No closure");
+ StringTable::the_table()->_weak_handles->oops_do(f);
}
-void StringTable::possibly_parallel_oops_do(OopClosure* f) {
- const int limit = the_table()->table_size();
+void StringTable::possibly_parallel_unlink(
+ OopStorage::ParState<false, false>* _par_state_string, BoolObjectClosure* cl,
+ int* processed, int* removed)
+{
+ DoNothingClosure dnc;
+ assert(cl != NULL, "No closure");
+ StringTableIsAliveCounter stiac(cl);
- for (;;) {
- // Grab next set of buckets to scan
- int start_idx = Atomic::add(ClaimChunkSize, &_parallel_claimed_idx) - ClaimChunkSize;
- if (start_idx >= limit) {
- // End of table
- break;
- }
+ _par_state_string->weak_oops_do(&stiac, &dnc);
- int end_idx = MIN2(limit, start_idx + ClaimChunkSize);
- buckets_oops_do(f, start_idx, end_idx);
- }
+ StringTable::the_table()->items_to_clean(stiac._count);
+ StringTable::the_table()->check_concurrent_work();
+ *processed = (int) stiac._count_total;
+ *removed = (int) stiac._count;
}
-// This verification is part of Universe::verify() and needs to be quick.
-// See StringTable::verify_and_compare() below for exhaustive verification.
-void StringTable::verify() {
- for (int i = 0; i < the_table()->table_size(); ++i) {
- HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
- for ( ; p != NULL; p = p->next()) {
- oop s = string_object_no_keepalive(p);
- guarantee(s != NULL, "interned string is NULL");
- unsigned int h = hash_string(s);
- guarantee(p->hash() == h, "broken hash in string table entry");
- guarantee(the_table()->hash_to_index(h) == i,
- "wrong index in string table");
- }
- }
+void StringTable::possibly_parallel_oops_do(
+ OopStorage::ParState<false /* concurrent */, false /* const */>*
+ _par_state_string, OopClosure* f)
+{
+ assert(f != NULL, "No closure");
+ _par_state_string->oops_do(f);
}
-void StringTable::dump(outputStream* st, bool verbose) {
- if (!verbose) {
- the_table()->print_table_statistics(st, "StringTable", string_object_no_keepalive);
- } else {
- Thread* THREAD = Thread::current();
- st->print_cr("VERSION: 1.1");
- for (int i = 0; i < the_table()->table_size(); ++i) {
- HashtableEntry<oop, mtSymbol>* p = the_table()->bucket(i);
- for ( ; p != NULL; p = p->next()) {
- oop s = string_object_no_keepalive(p);
- 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);
+struct StringTableDeleteCheck {
+ 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 {
- ResourceMark rm(THREAD);
- int utf8_length = length;
- char* utf8_string;
+ return false;
+ }
+ }
+};
- 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);
+struct StringTableDoDelete {
+ long _count;
+ StringTableDoDelete() : _count(0) {}
+ void operator()(WeakHandle<vm_string_table_data>* val) {
+ ++_count;
}
+};
- st->print("%d: ", utf8_length);
- HashtableTextDump::put_utf8(st, utf8_string, utf8_length);
+void StringTable::grow(JavaThread* jt) {
+ StringTableHash::GrowTask gt(_local_table);
+ if (!gt.prepare(jt)) {
+ return;
}
- st->cr();
+ log_trace(stringtable)("Started to growed");
+ {
+ TraceTime timer("Grow", TRACETIME_LOG(Debug, stringtable, perf));
+ while(gt.doTask(jt)) {
+ gt.pause(jt);
+ {
+ ThreadBlockInVM tbivm(jt);
}
+ gt.cont(jt);
}
}
+ gt.done(jt);
+ _current_size = table_size(jt);
+ log_debug(stringtable)("Growed to size:" SIZE_FORMAT, _current_size);
}
-StringTable::VerifyRetTypes StringTable::compare_entries(
- int bkt1, int e_cnt1,
- HashtableEntry<oop, mtSymbol>* e_ptr1,
- int bkt2, int e_cnt2,
- HashtableEntry<oop, mtSymbol>* e_ptr2) {
- // These entries are sanity checked by verify_and_compare_entries()
- // before this function is called.
- oop str1 = string_object_no_keepalive(e_ptr1);
- oop str2 = string_object_no_keepalive(e_ptr2);
-
- if (str1 == str2) {
- tty->print_cr("ERROR: identical oop values (0x" PTR_FORMAT ") "
- "in entry @ bucket[%d][%d] and entry @ bucket[%d][%d]",
- p2i(str1), bkt1, e_cnt1, bkt2, e_cnt2);
- return _verify_fail_continue;
+void StringTable::clean_dead_entries(JavaThread* jt) {
+ StringTableHash::BulkDeleteTask bdt(_local_table);
+ if (!bdt.prepare(jt)) {
+ return;
}
- if (java_lang_String::equals(str1, str2)) {
- tty->print_cr("ERROR: identical String values in entry @ "
- "bucket[%d][%d] and entry @ bucket[%d][%d]",
- bkt1, e_cnt1, bkt2, e_cnt2);
- return _verify_fail_continue;
+ StringTableDeleteCheck stdc;
+ StringTableDoDelete stdd;
+ bool interrupted = false;
+ {
+ TraceTime timer("Clean", TRACETIME_LOG(Debug, stringtable, perf));
+ while(bdt.doTask(jt, stdc, stdd)) {
+ bdt.pause(jt);
+ {
+ ThreadBlockInVM tbivm(jt);
}
+ if (!bdt.cont(jt)) {
+ interrupted = true;
+ break;
+ }
+ }
+ }
+ if (interrupted) {
+ _has_work = true;
+ } else {
+ bdt.done(jt);
+ }
+ log_debug(stringtable)("Cleaned %ld of %ld", stdc._count, stdc._item);
+}
- return _verify_pass;
+void StringTable::check_concurrent_work() {
+ if (_has_work) {
+ return;
+ }
+ double fact = StringTable::get_load_factor();
+ double dead_fact = 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_fact > fact) ||
+ (fact > PREF_AVG_LIST_LEN) ||
+ (dead_fact > CLEAN_DEAD_HIGH_WATER_MARK)) {
+ log_debug(stringtable)("Concurrent work triggered, live factor:%g dead factor:%g",
+ fact, dead_fact);
+ trigger_concurrent_work();
+ }
}
-StringTable::VerifyRetTypes StringTable::verify_entry(int bkt, int e_cnt,
- HashtableEntry<oop, mtSymbol>* e_ptr,
- StringTable::VerifyMesgModes mesg_mode) {
+void StringTable::concurrent_work(JavaThread* jt) {
+ _has_work = false;
+ double fact = get_load_factor();
+ log_debug(stringtable, perf)("Concurrent work, live factor: %g", fact);
+ // We prefer growing, since that also removes dead items
+ if (fact > PREF_AVG_LIST_LEN && !_local_table->is_max_size_reached()) {
+ grow(jt);
+ } else {
+ clean_dead_entries(jt);
+ }
+}
- VerifyRetTypes ret = _verify_pass; // be optimistic
+void StringTable::do_concurrent_work(JavaThread* jt) {
+ StringTable::the_table()->concurrent_work(jt);
+}
- oop str = string_object_no_keepalive(e_ptr);
- if (str == NULL) {
- if (mesg_mode == _verify_with_mesgs) {
- tty->print_cr("ERROR: NULL oop value in entry @ bucket[%d][%d]", bkt,
- e_cnt);
- }
- // NULL oop means no more verifications are possible
- return _verify_fail_done;
+bool StringTable::do_rehash() {
+ if (!_local_table->is_safepoint_safe()) {
+ return false;
}
- if (str->klass() != SystemDictionary::String_klass()) {
- if (mesg_mode == _verify_with_mesgs) {
- tty->print_cr("ERROR: oop is not a String in entry @ bucket[%d][%d]",
- bkt, e_cnt);
- }
- // not a String means no more verifications are possible
- return _verify_fail_done;
+ // We use max size
+ StringTableHash* new_table = new StringTableHash(END_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;
}
- unsigned int h = hash_string(str);
- if (e_ptr->hash() != h) {
- if (mesg_mode == _verify_with_mesgs) {
- tty->print_cr("ERROR: broken hash value in entry @ bucket[%d][%d], "
- "bkt_hash=%d, str_hash=%d", bkt, e_cnt, e_ptr->hash(), h);
+ // free old table
+ delete _local_table;
+ _local_table = new_table;
+
+ return true;
+}
+
+void StringTable::try_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;
}
- ret = _verify_fail_continue;
+ // Already rehashed.
+ if (rehashed) {
+ log_warning(stringtable)("Rehashing already done, still long lists.");
+ trigger_concurrent_work();
+ _needs_rehashing = false;
+ return;
}
- if (the_table()->hash_to_index(h) != bkt) {
- if (mesg_mode == _verify_with_mesgs) {
- tty->print_cr("ERROR: wrong index value for entry @ bucket[%d][%d], "
- "str_hash=%d, hash_to_index=%d", bkt, e_cnt, h,
- the_table()->hash_to_index(h));
+ murmur_seed = AltHashing::compute_seed();
+ {
+ if (do_rehash()) {
+ rehashed = true;
+ } else {
+ log_info(stringtable)("Resizes in progress rehashing skipped.");
}
- ret = _verify_fail_continue;
}
-
- return ret;
+ _needs_rehashing = false;
}
-// See StringTable::verify() above for the quick verification that is
-// part of Universe::verify(). This verification is exhaustive and
-// reports on every issue that is found. StringTable::verify() only
-// reports on the first issue that is found.
-//
-// StringTable::verify_entry() checks:
-// - oop value != NULL (same as verify())
-// - oop value is a String
-// - hash(String) == hash in entry (same as verify())
-// - index for hash == index of entry (same as verify())
-//
-// StringTable::compare_entries() checks:
-// - oops are unique across all entries
-// - String values are unique across all entries
-//
-int StringTable::verify_and_compare_entries() {
- assert(StringTable_lock->is_locked(), "sanity check");
+void StringTable::rehash_table() {
+ StringTable::the_table()->try_rehash_table();
+}
- int fail_cnt = 0;
+oop StringTable::lookup_shared(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((const char*)name, hash, len);
+}
- // first, verify all the entries individually:
- for (int bkt = 0; bkt < the_table()->table_size(); bkt++) {
- HashtableEntry<oop, mtSymbol>* e_ptr = the_table()->bucket(bkt);
- for (int e_cnt = 0; e_ptr != NULL; e_ptr = e_ptr->next(), e_cnt++) {
- VerifyRetTypes ret = verify_entry(bkt, e_cnt, e_ptr, _verify_with_mesgs);
- if (ret != _verify_pass) {
- fail_cnt++;
- }
+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 {
+ size_t operator()(WeakHandle<vm_string_table_data>* val) {
+ oop s = val->peek();
+ if (s == NULL) {
+ // Dead
+ return 0;
}
+ return literal_size(s);
+ };
+};
- // Optimization: if the above check did not find any failures, then
- // the comparison loop below does not need to call verify_entry()
- // before calling compare_entries(). If there were failures, then we
- // have to call verify_entry() to see if the entry can be passed to
- // compare_entries() safely. When we call verify_entry() in the loop
- // below, we do so quietly to void duplicate messages and we don't
- // increment fail_cnt because the failures have already been counted.
- bool need_entry_verify = (fail_cnt != 0);
+void StringTable::print_table_statistics(outputStream* st,
+ const char* table_name) {
+ SizeFunc sz;
+ _local_table->statistics_to(Thread::current(), sz, st, table_name);
+}
- // second, verify all entries relative to each other:
- for (int bkt1 = 0; bkt1 < the_table()->table_size(); bkt1++) {
- HashtableEntry<oop, mtSymbol>* e_ptr1 = the_table()->bucket(bkt1);
- for (int e_cnt1 = 0; e_ptr1 != NULL; e_ptr1 = e_ptr1->next(), e_cnt1++) {
- if (need_entry_verify) {
- VerifyRetTypes ret = verify_entry(bkt1, e_cnt1, e_ptr1,
- _verify_quietly);
- if (ret == _verify_fail_done) {
- // cannot use the current entry to compare against other entries
- continue;
- }
+class PrintString {
+ 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);
- for (int bkt2 = bkt1; bkt2 < the_table()->table_size(); bkt2++) {
- HashtableEntry<oop, mtSymbol>* e_ptr2 = the_table()->bucket(bkt2);
- int e_cnt2;
- for (e_cnt2 = 0; e_ptr2 != NULL; e_ptr2 = e_ptr2->next(), e_cnt2++) {
- if (bkt1 == bkt2 && e_cnt2 <= e_cnt1) {
- // skip the entries up to and including the one that
- // we're comparing against
- continue;
- }
+ if (length <= 0) {
+ _st->print("%d: ", length);
+ } else {
+ ResourceMark rm(_thr);
+ int utf8_length = length;
+ char* utf8_string;
- if (need_entry_verify) {
- VerifyRetTypes ret = verify_entry(bkt2, e_cnt2, e_ptr2,
- _verify_quietly);
- if (ret == _verify_fail_done) {
- // cannot compare against this entry
- continue;
- }
+ 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);
}
- // compare two entries, report and count any failures:
- if (compare_entries(bkt1, e_cnt1, e_ptr1, bkt2, e_cnt2, e_ptr2)
- != _verify_pass) {
- fail_cnt++;
- }
- }
+ _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) {
+ the_table()->print_table_statistics(st, "StringTable");
+ } else {
+ Thread* thr = Thread::current();
+ ResourceMark rm(thr);
+ st->print_cr("VERSION: 1.1");
+ PrintString ps(thr, st);
+ if (!the_table()->_local_table->try_scan(thr, ps)) {
+ st->print_cr("dump unavailable at this moment");
}
}
- return fail_cnt;
}
-// Create a new table and using alternate hash code, populate the new table
-// with the existing strings. Set flag to use the alternate hash code afterwards.
-void StringTable::rehash_table() {
- assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
- // This should never happen with -Xshare:dump but it might in testing mode.
- if (DumpSharedSpaces) return;
- StringTable* new_table = new StringTable();
-
- // Rehash the table
- the_table()->move_to(new_table);
-
- // Delete the table and buckets (entries are reused in new table).
- delete _the_table;
- // Don't check if we need rehashing until the table gets unbalanced again.
- // Then rehash with a new global seed.
- _needs_rehashing = false;
- _the_table = new_table;
+class VerifyStrings {
+ 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 (!the_table()->_local_table->try_scan(thr, vs)) {
+ log_info(stringtable)("verify unavailable at this moment");
+ }
}
// Utility for dumping strings
StringtableDCmd::StringtableDCmd(outputStream* output, bool heap) :
DCmdWithParser(output, heap),
@@ -676,11 +738,12 @@
oop StringTable::create_archived_string(oop s, Thread* THREAD) {
assert(DumpSharedSpaces, "this function is only used with -Xshare:dump");
oop new_s = NULL;
typeArrayOop v = java_lang_String::value_no_keepalive(s);
- typeArrayOop new_v = (typeArrayOop)MetaspaceShared::archive_heap_object(v, THREAD);
+ typeArrayOop new_v =
+ (typeArrayOop)MetaspaceShared::archive_heap_object(v, THREAD);
if (new_v == NULL) {
return NULL;
}
new_s = MetaspaceShared::archive_heap_object(s, THREAD);
if (new_s == NULL) {
@@ -690,67 +753,69 @@
// adjust the pointer to the 'value' field in the new String oop
java_lang_String::set_value_raw(new_s, new_v);
return new_s;
}
-bool StringTable::copy_shared_string(GrowableArray<MemRegion> *string_space,
- CompactStringTableWriter* writer) {
- assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
-
- Thread* THREAD = Thread::current();
- for (int i = 0; i < the_table()->table_size(); ++i) {
- HashtableEntry<oop, mtSymbol>* bucket = the_table()->bucket(i);
- for ( ; bucket != NULL; bucket = bucket->next()) {
- oop s = string_object_no_keepalive(bucket);
+struct CopyArchive {
+ CompactStringTableWriter* _writer;
+ CopyArchive(CompactStringTableWriter* writer) : _writer(writer) {}
+ bool operator()(WeakHandle<vm_string_table_data>* val) {
+ oop s = val->peek();
+ if (s == NULL) {
+ return true;
+ }
unsigned int hash = java_lang_String::hash_code(s);
if (hash == 0) {
- continue;
+ return true;
}
java_lang_String::set_hash(s, hash);
- oop new_s = create_archived_string(s, THREAD);
+ oop new_s = StringTable::create_archived_string(s, Thread::current());
if (new_s == NULL) {
- continue;
+ return true;
}
- // set the archived string in bucket
- set_string_object(bucket, new_s);
-
+ val->replace(new_s);
// add to the compact table
- writer->add(hash, new_s);
- }
+ _writer->add(hash, new_s);
+ return true;
}
+};
- return true;
+void StringTable::copy_shared_string(CompactStringTableWriter* writer) {
+ assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
+
+ CopyArchive copy(writer);
+ StringTable::the_table()->_local_table->do_scan(Thread::current(), copy);
}
-void StringTable::write_to_archive(GrowableArray<MemRegion> *string_space) {
+void StringTable::write_to_archive() {
assert(MetaspaceShared::is_heap_object_archiving_allowed(), "must be");
_shared_table.reset();
- int num_buckets = the_table()->number_of_entries() /
- SharedSymbolTableBucketSize;
+ int num_buckets = the_table()->_items / SharedSymbolTableBucketSize;
// calculation of num_buckets can result in zero buckets, we need at least one
CompactStringTableWriter writer(num_buckets > 1 ? num_buckets : 1,
&MetaspaceShared::stats()->string);
// Copy the interned strings into the "string space" within the java heap
- if (copy_shared_string(string_space, &writer)) {
+ copy_shared_string(&writer);
writer.dump(&_shared_table);
- }
}
void StringTable::serialize(SerializeClosure* soc) {
_shared_table.set_type(CompactHashtable<oop, char>::_string_table);
_shared_table.serialize(soc);
if (soc->writing()) {
- _shared_table.reset(); // Sanity. Make sure we don't use the shared table at dump time
+ // Sanity. Make sure we don't use the shared table at dump time
+ _shared_table.reset();
} else if (!_shared_string_mapped) {
_shared_table.reset();
}
}
void StringTable::shared_oops_do(OopClosure* f) {
_shared_table.oops_do(f);
}
+
#endif //INCLUDE_CDS_JAVA_HEAP
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