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src/hotspot/share/classfile/symbolTable.hpp
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@@ -1,7 +1,7 @@
/*
- * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2018, 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.
@@ -24,27 +24,15 @@
#ifndef SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
#define SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
#include "memory/allocation.hpp"
+#include "memory/padded.hpp"
#include "oops/symbol.hpp"
+#include "utilities/concurrentHashTable.hpp"
#include "utilities/hashtable.hpp"
-// The symbol table holds all Symbol*s and corresponding interned strings.
-// Symbol*s and literal strings should be canonicalized.
-//
-// The interned strings are created lazily.
-//
-// It is implemented as an open hash table with a fixed number of buckets.
-//
-// %note:
-// - symbolTableEntrys are allocated in blocks to reduce the space overhead.
-
-class BoolObjectClosure;
-class outputStream;
-class SerializeClosure;
-
// TempNewSymbol acts as a handle class in a handle/body idiom and is
// responsible for proper resource management of the body (which is a Symbol*).
// The body is resource managed by a reference counting scheme.
// TempNewSymbol can therefore be used to properly hold a newly created or referenced
// Symbol* temporarily in scope.
@@ -57,11 +45,11 @@
// symbol table and add to the symbol's reference count.
// probe() and lookup_only() will increment the refcount if symbol is found.
class TempNewSymbol : public StackObj {
Symbol* _temp;
- public:
+public:
TempNewSymbol() : _temp(NULL) {}
// Conversion from a Symbol* to a TempNewSymbol.
// Does not increment the current reference count.
TempNewSymbol(Symbol *s) : _temp(s) {}
@@ -95,178 +83,180 @@
bool operator == (Symbol* o) const { return _temp == o; }
operator Symbol*() { return _temp; }
};
template <class T, class N> class CompactHashtable;
+class CompactSymbolTableWriter;
+class SerializeClosure;
+
+class SymbolTableConfig;
+typedef ConcurrentHashTable<Symbol*,
+ SymbolTableConfig, mtSymbol> SymbolTableHash;
-class SymbolTable : public RehashableHashtable<Symbol*, mtSymbol> {
+class SymbolTableCreateEntry;
+
+class SymbolTable : public CHeapObj<mtSymbol> {
friend class VMStructs;
+ friend class Symbol;
friend class ClassFileParser;
+ friend class SymbolTableConfig;
+ friend class SymbolTableCreateEntry;
private:
+ static void delete_symbol(Symbol* sym);
+ void grow(JavaThread* jt);
+ void clean_dead_entries(JavaThread* jt);
+
// The symbol table
static SymbolTable* _the_table;
+ // Shared symbol table.
+ static CompactHashtable<Symbol*, char> _shared_table;
+ static volatile bool _lookup_shared_first;
+ static volatile bool _alt_hash;
+
+ // For statistics
+ volatile size_t _symbols_removed;
+ volatile size_t _symbols_counted;
+ SymbolTableHash* _local_table;
+ size_t _current_size;
+ volatile bool _has_work;
// Set if one bucket is out of balance due to hash algorithm deficiency
- static bool _needs_rehashing;
- static bool _lookup_shared_first;
+ volatile bool _needs_rehashing;
- // For statistics
- static int _symbols_removed;
- static int _symbols_counted;
+ volatile size_t _items_count;
+ volatile size_t _uncleaned_items_count;
- // shared symbol table.
- static CompactHashtable<Symbol*, char> _shared_table;
+ double get_load_factor();
+ double get_dead_factor();
- Symbol* allocate_symbol(const u1* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
+ void check_concurrent_work();
+ void trigger_concurrent_work();
+
+ static void item_added();
+ static void item_removed();
+ static void set_item_clean_count(size_t ncl);
+ static void mark_item_clean_count();
+
+ SymbolTable();
+
+ Symbol* allocate_symbol(const char* name, int len, bool c_heap, TRAPS); // Assumes no characters larger than 0x7F
+ Symbol* do_lookup(const char* name, int len, uintx hash);
+ Symbol* do_add_if_needed(const char* name, int len, uintx hash, bool heap, TRAPS);
// Adding elements
- Symbol* basic_add(int index, u1* name, int len, unsigned int hashValue,
- bool c_heap, TRAPS);
- bool basic_add(ClassLoaderData* loader_data,
- const constantPoolHandle& cp, int names_count,
- const char** names, int* lengths, int* cp_indices,
- unsigned int* hashValues, TRAPS);
+ static void add(ClassLoaderData* loader_data,
+ const constantPoolHandle& cp, int names_count,
+ const char** names, int* lengths, int* cp_indices,
+ unsigned int* hashValues, TRAPS);
static void new_symbols(ClassLoaderData* loader_data,
const constantPoolHandle& cp, int names_count,
const char** name, int* lengths,
int* cp_indices, unsigned int* hashValues,
TRAPS) {
add(loader_data, cp, names_count, name, lengths, cp_indices, hashValues, THREAD);
}
static Symbol* lookup_shared(const char* name, int len, unsigned int hash);
- Symbol* lookup_dynamic(int index, const char* name, int len, unsigned int hash);
- Symbol* lookup(int index, const char* name, int len, unsigned int hash);
-
- SymbolTable()
- : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>)) {}
-
- SymbolTable(HashtableBucket<mtSymbol>* t, int number_of_entries)
- : RehashableHashtable<Symbol*, mtSymbol>(SymbolTableSize, sizeof (HashtableEntry<Symbol*, mtSymbol>), t,
- number_of_entries) {}
+ Symbol* lookup_dynamic(const char* name, int len, unsigned int hash);
+ Symbol* lookup_common(const char* name, int len, unsigned int hash);
// Arena for permanent symbols (null class loader) that are never unloaded
static Arena* _arena;
static Arena* arena() { return _arena; } // called for statistics
static void initialize_symbols(int arena_alloc_size = 0);
- static volatile int _parallel_claimed_idx;
+ void concurrent_work(JavaThread* jt);
+ void print_table_statistics(outputStream* st, const char* table_name);
+
+ void try_rehash_table();
+ bool do_rehash();
- typedef SymbolTable::BucketUnlinkContext BucketUnlinkContext;
- // Release any dead symbols. Unlinked bucket entries are collected in the given
- // context to be freed later.
- // This allows multiple threads to work on the table at once.
- static void buckets_unlink(int start_idx, int end_idx, BucketUnlinkContext* context);
public:
+ // The symbol table
+ static SymbolTable* the_table() { return _the_table; }
+ size_t table_size(Thread* thread = NULL);
+
enum {
symbol_alloc_batch_size = 8,
// Pick initial size based on java -version size measurements
- symbol_alloc_arena_size = 360*K
+ symbol_alloc_arena_size = 360*K // TODO (revisit)
};
- // The symbol table
- static SymbolTable* the_table() { return _the_table; }
-
- // Size of one bucket in the string table. Used when checking for rollover.
- static uint bucket_size() { return sizeof(HashtableBucket<mtSymbol>); }
-
static void create_table() {
assert(_the_table == NULL, "One symbol table allowed.");
_the_table = new SymbolTable();
initialize_symbols(symbol_alloc_arena_size);
}
- static unsigned int hash_symbol(const char* s, int len);
- static unsigned int hash_shared_symbol(const char* s, int len);
+ static void unlink() {
+ do_check_concurrent_work();
+ }
+ static void do_check_concurrent_work();
+ static void do_concurrent_work(JavaThread* jt);
+ static bool has_work() { return the_table()->_has_work; }
+ // Probing
static Symbol* lookup(const char* name, int len, TRAPS);
// lookup only, won't add. Also calculate hash.
static Symbol* lookup_only(const char* name, int len, unsigned int& hash);
// Only copy to C string to be added if lookup failed.
static Symbol* lookup(const Symbol* sym, int begin, int end, TRAPS);
-
- static void release(Symbol* sym);
-
- // Look up the address of the literal in the SymbolTable for this Symbol*
- static Symbol** lookup_symbol_addr(Symbol* sym);
-
// jchar (UTF16) version of lookups
static Symbol* lookup_unicode(const jchar* name, int len, TRAPS);
static Symbol* lookup_only_unicode(const jchar* name, int len, unsigned int& hash);
-
- static void add(ClassLoaderData* loader_data,
- const constantPoolHandle& cp, int names_count,
- const char** names, int* lengths, int* cp_indices,
- unsigned int* hashValues, TRAPS);
-
- // Release any dead symbols
- static void unlink() {
- int processed = 0;
- int removed = 0;
- unlink(&processed, &removed);
- }
- static void unlink(int* processed, int* removed);
- // Release any dead symbols, possibly parallel version
- static void possibly_parallel_unlink(int* processed, int* removed);
-
- // iterate over symbols
- static void symbols_do(SymbolClosure *cl);
- static void metaspace_pointers_do(MetaspaceClosure* it);
+ // Needed for preloading classes in signatures when compiling.
+ // Returns the symbol is already present in symbol table, otherwise
+ // NULL. NO ALLOCATION IS GUARANTEED!
+ static Symbol* probe(const char* name, int len) {
+ unsigned int ignore_hash;
+ return lookup_only(name, len, ignore_hash);
+ }
+ static Symbol* probe_unicode(const jchar* name, int len) {
+ unsigned int ignore_hash;
+ return lookup_only_unicode(name, len, ignore_hash);
+ }
// Symbol creation
static Symbol* new_symbol(const char* utf8_buffer, int length, TRAPS) {
assert(utf8_buffer != NULL, "just checking");
return lookup(utf8_buffer, length, THREAD);
}
- static Symbol* new_symbol(const char* name, TRAPS) {
+ static Symbol* new_symbol(const char* name, TRAPS) {
return new_symbol(name, (int)strlen(name), THREAD);
}
- static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
+ static Symbol* new_symbol(const Symbol* sym, int begin, int end, TRAPS) {
assert(begin <= end && end <= sym->utf8_length(), "just checking");
return lookup(sym, begin, end, THREAD);
}
-
// Create a symbol in the arena for symbols that are not deleted
static Symbol* new_permanent_symbol(const char* name, TRAPS);
- // Symbol lookup
- static Symbol* lookup(int index, const char* name, int len, TRAPS);
+ // Rehash the string table if it gets out of balance
+ static void rehash_table();
+ static bool needs_rehashing()
+ { return SymbolTable::the_table()->_needs_rehashing; }
- // Needed for preloading classes in signatures when compiling.
- // Returns the symbol is already present in symbol table, otherwise
- // NULL. NO ALLOCATION IS GUARANTEED!
- static Symbol* probe(const char* name, int len) {
- unsigned int ignore_hash;
- return lookup_only(name, len, ignore_hash);
- }
- static Symbol* probe_unicode(const jchar* name, int len) {
- unsigned int ignore_hash;
- return lookup_only_unicode(name, len, ignore_hash);
- }
+ // Heap dumper and CDS
+ static void symbols_do(SymbolClosure *cl);
- // Histogram
- static void print_histogram() PRODUCT_RETURN;
- static void print() PRODUCT_RETURN;
+ // Sharing
+private:
+ static void copy_shared_symbol_table(CompactSymbolTableWriter* ch_table);
+public:
+ static void write_to_archive() NOT_CDS_RETURN;
+ static void serialize(SerializeClosure* soc) NOT_CDS_RETURN;
+ static void metaspace_pointers_do(MetaspaceClosure* it);
+ // Jcmd
+ static void dump(outputStream* st, bool verbose=false);
// Debugging
static void verify();
- static void dump(outputStream* st, bool verbose=false);
static void read(const char* filename, TRAPS);
- // Sharing
- static void write_to_archive();
- static void serialize(SerializeClosure* soc);
- static u4 encode_shared(Symbol* sym);
- static Symbol* decode_shared(u4 offset);
-
- // Rehash the symbol table if it gets out of balance
- static void rehash_table();
- static bool needs_rehashing() { return _needs_rehashing; }
- // Parallel chunked scanning
- static void clear_parallel_claimed_index() { _parallel_claimed_idx = 0; }
- static int parallel_claimed_index() { return _parallel_claimed_idx; }
+ // Histogram
+ static void print_histogram() PRODUCT_RETURN;
};
#endif // SHARE_VM_CLASSFILE_SYMBOLTABLE_HPP
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