edcd4cb94b
Support saving interned strings in shared CDS archive. Reviewed-by: coleenp, iklam, pliden
467 lines
14 KiB
C++
467 lines
14 KiB
C++
/*
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* Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#ifndef SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP
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#define SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP
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#include "classfile/stringTable.hpp"
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#include "classfile/symbolTable.hpp"
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#include "memory/allocation.inline.hpp"
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#include "oops/oop.inline.hpp"
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#include "oops/symbol.hpp"
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#include "services/diagnosticCommand.hpp"
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#include "utilities/hashtable.hpp"
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class NumberSeq;
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// Stats for symbol tables in the CDS archive
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class CompactHashtableStats VALUE_OBJ_CLASS_SPEC {
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public:
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int hashentry_count;
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int hashentry_bytes;
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int bucket_count;
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int bucket_bytes;
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};
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/////////////////////////////////////////////////////////////////////////
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//
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// The compact hash table writer. Used at dump time for writing out
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// the compact table to the shared archive.
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//
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// At dump time, the CompactHashtableWriter obtains all entries from the
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// symbol/string table and adds them to a new temporary hash table. The hash
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// table size (number of buckets) is calculated using
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// '(num_entries + bucket_size - 1) / bucket_size'. The default bucket
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// size is 4 and can be changed by -XX:SharedSymbolTableBucketSize option.
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// 4 is chosen because it produces smaller sized bucket on average for
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// faster lookup. It also has relatively small number of empty buckets and
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// good distribution of the entries.
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//
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// We use a simple hash function (hash % num_bucket) for the table.
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// The new table is compacted when written out. Please see comments
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// above the CompactHashtable class for the table layout detail. The bucket
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// offsets are written to the archive as part of the compact table. The
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// bucket offset is encoded in the low 30-bit (0-29) and the bucket type
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// (regular or compact) are encoded in bit[31, 30]. For buckets with more
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// than one entry, both hash and entry offset are written to the
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// table. For buckets with only one entry, only the entry offset is written
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// to the table and the buckets are tagged as compact in their type bits.
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// Buckets without entry are skipped from the table. Their offsets are
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// still written out for faster lookup.
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//
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class CompactHashtableWriter: public StackObj {
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public:
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class Entry: public CHeapObj<mtSymbol> {
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Entry* _next;
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unsigned int _hash;
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void* _literal;
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public:
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Entry(unsigned int hash, Symbol *symbol) : _next(NULL), _hash(hash), _literal(symbol) {}
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Entry(unsigned int hash, oop string) : _next(NULL), _hash(hash), _literal(string) {}
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void *value() {
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return _literal;
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}
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Symbol *symbol() {
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return (Symbol*)_literal;
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}
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oop string() {
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return (oop)_literal;
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}
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unsigned int hash() {
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return _hash;
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}
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Entry *next() {return _next;}
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void set_next(Entry *p) {_next = p;}
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}; // class CompactHashtableWriter::Entry
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private:
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static int number_of_buckets(int num_entries);
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int _type;
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int _num_entries;
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int _num_buckets;
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juint* _bucket_sizes;
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Entry** _buckets;
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int _required_bytes;
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CompactHashtableStats* _stats;
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public:
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// This is called at dump-time only
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CompactHashtableWriter(int table_type, int num_entries, CompactHashtableStats* stats);
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~CompactHashtableWriter();
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int get_required_bytes() {
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return _required_bytes;
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}
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void add(unsigned int hash, Symbol* symbol) {
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add(hash, new Entry(hash, symbol));
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}
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void add(unsigned int hash, oop string) {
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add(hash, new Entry(hash, string));
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}
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private:
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void add(unsigned int hash, Entry* entry);
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juint* dump_table(juint* p, juint** first_bucket, NumberSeq* summary);
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juint* dump_buckets(juint* table, juint* p, NumberSeq* summary);
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public:
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void dump(char** top, char* end);
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const char* table_name();
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};
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#define REGULAR_BUCKET_TYPE 0
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#define COMPACT_BUCKET_TYPE 1
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#define TABLEEND_BUCKET_TYPE 3
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#define BUCKET_OFFSET_MASK 0x3FFFFFFF
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#define BUCKET_OFFSET(info) ((info) & BUCKET_OFFSET_MASK)
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#define BUCKET_TYPE_SHIFT 30
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#define BUCKET_TYPE(info) (((info) & ~BUCKET_OFFSET_MASK) >> BUCKET_TYPE_SHIFT)
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#define BUCKET_INFO(offset, type) (((type) << BUCKET_TYPE_SHIFT) | ((offset) & BUCKET_OFFSET_MASK))
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/////////////////////////////////////////////////////////////////////////////
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//
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// CompactHashtable is used to stored the CDS archive's symbol/string table. Used
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// at runtime only to access the compact table from the archive.
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//
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// Because these tables are read-only (no entries can be added/deleted) at run-time
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// and tend to have large number of entries, we try to minimize the footprint
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// cost per entry.
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//
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// Layout of compact table in the shared archive:
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//
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// uintx base_address;
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// juint num_entries;
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// juint num_buckets;
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// juint bucket_infos[num_buckets+1]; // bit[31,30]: type; bit[29-0]: offset
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// juint table[]
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//
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// -----------------------------------
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// | base_address | num_entries |
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// |---------------------------------|
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// | num_buckets | bucket_info0 |
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// |---------------------------------|
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// | bucket_info1 | bucket_info2 |
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// | bucket_info3 ... |
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// | .... | table_end_info |
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// |---------------------------------|
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// | entry0 |
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// | entry1 |
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// | entry2 |
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// | |
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// | ... |
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// -----------------------------------
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//
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// The size of the bucket_info table is 'num_buckets + 1'. Each entry of the
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// bucket_info table is a 32-bit encoding of the bucket type and bucket offset,
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// with the type in the left-most 2-bit and offset in the remaining 30-bit.
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// The last entry is a special type. It contains the offset of the last
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// bucket end. We use that information when traversing the compact table.
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//
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// There are two types of buckets, regular buckets and compact buckets. The
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// compact buckets have '01' in their highest 2-bit, and regular buckets have
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// '00' in their highest 2-bit.
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//
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// For normal buckets, each entry is 8 bytes in the table[]:
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// juint hash; /* symbol/string hash */
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// union {
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// juint offset; /* Symbol* sym = (Symbol*)(base_address + offset) */
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// narrowOop str; /* String narrowOop encoding */
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// }
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//
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//
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// For compact buckets, each entry has only the 4-byte 'offset' in the table[].
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//
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// See CompactHashtable::lookup() for how the table is searched at runtime.
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// See CompactHashtableWriter::dump() for how the table is written at CDS
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// dump time.
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//
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template <class T, class N> class CompactHashtable VALUE_OBJ_CLASS_SPEC {
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friend class VMStructs;
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public:
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enum CompactHashtableType {
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_symbol_table = 0,
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_string_table = 1
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};
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private:
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CompactHashtableType _type;
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uintx _base_address;
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juint _entry_count;
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juint _bucket_count;
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juint _table_end_offset;
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juint* _buckets;
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inline Symbol* lookup_entry(CompactHashtable<Symbol*, char>* const t,
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juint* addr, const char* name, int len) {
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Symbol* sym = (Symbol*)((void*)(_base_address + *addr));
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if (sym->equals(name, len)) {
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assert(sym->refcount() == -1, "must be shared");
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return sym;
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}
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return NULL;
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}
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inline oop lookup_entry(CompactHashtable<oop, char>* const t,
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juint* addr, const char* name, int len) {
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narrowOop obj = (narrowOop)(*addr);
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oop string = oopDesc::decode_heap_oop(obj);
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if (java_lang_String::equals(string, (jchar*)name, len)) {
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return string;
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}
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return NULL;
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}
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public:
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CompactHashtable() {
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_entry_count = 0;
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_bucket_count = 0;
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_table_end_offset = 0;
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_buckets = 0;
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}
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const char* init(CompactHashtableType type, const char *buffer);
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void reset() {
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_entry_count = 0;
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_bucket_count = 0;
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_table_end_offset = 0;
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_buckets = 0;
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}
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// Lookup an entry from the compact table
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inline T lookup(const N* name, unsigned int hash, int len) {
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if (_entry_count > 0) {
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assert(!DumpSharedSpaces, "run-time only");
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int index = hash % _bucket_count;
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juint bucket_info = _buckets[index];
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juint bucket_offset = BUCKET_OFFSET(bucket_info);
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int bucket_type = BUCKET_TYPE(bucket_info);
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juint* bucket = _buckets + bucket_offset;
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juint* bucket_end = _buckets;
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if (bucket_type == COMPACT_BUCKET_TYPE) {
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// the compact bucket has one entry with entry offset only
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T res = lookup_entry(this, &bucket[0], name, len);
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if (res != NULL) {
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return res;
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}
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} else {
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// This is a regular bucket, which has more than one
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// entries. Each entry is a pair of entry (hash, offset).
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// Seek until the end of the bucket.
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bucket_end += BUCKET_OFFSET(_buckets[index + 1]);
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while (bucket < bucket_end) {
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unsigned int h = (unsigned int)(bucket[0]);
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if (h == hash) {
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T res = lookup_entry(this, &bucket[1], name, len);
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if (res != NULL) {
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return res;
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}
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}
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bucket += 2;
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}
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}
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}
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return NULL;
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}
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// iterate over symbols
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void symbols_do(SymbolClosure *cl);
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// iterate over strings
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void oops_do(OopClosure* f);
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};
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////////////////////////////////////////////////////////////////////////
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//
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// Read/Write the contents of a hashtable textual dump (created by
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// SymbolTable::dump and StringTable::dump).
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// Because the dump file may be big (hundred of MB in extreme cases),
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// we use mmap for fast access when reading it.
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//
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class HashtableTextDump VALUE_OBJ_CLASS_SPEC {
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int _fd;
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const char* _base;
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const char* _p;
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const char* _end;
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const char* _filename;
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size_t _size;
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int _prefix_type;
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int _line_no;
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public:
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HashtableTextDump(const char* filename);
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~HashtableTextDump();
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enum {
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SymbolPrefix = 1 << 0,
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StringPrefix = 1 << 1,
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Unknown = 1 << 2
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};
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void quit(const char* err, const char* msg);
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inline int remain() {
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return (int)(_end - _p);
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}
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void corrupted(const char *p, const char *msg);
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inline void corrupted_if(bool cond) {
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if (cond) {
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corrupted(_p, NULL);
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}
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}
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bool skip_newline();
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int skip(char must_be_char);
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void skip_past(char c);
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void check_version(const char* ver);
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inline bool get_num(char delim, int *utf8_length) {
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const char* p = _p;
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const char* end = _end;
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int num = 0;
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while (p < end) {
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char c = *p ++;
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if ('0' <= c && c <= '9') {
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num = num * 10 + (c - '0');
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} else if (c == delim) {
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_p = p;
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*utf8_length = num;
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return true;
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} else {
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// Not [0-9], not 'delim'
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return false;
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}
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}
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corrupted(_end, "Incorrect format");
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ShouldNotReachHere();
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return false;
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}
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void scan_prefix_type();
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int scan_prefix(int* utf8_length);
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int scan_string_prefix();
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int scan_symbol_prefix();
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jchar unescape(const char* from, const char* end, int count);
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void get_utf8(char* utf8_buffer, int utf8_length);
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static void put_utf8(outputStream* st, const char* utf8_string, int utf8_length);
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};
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///////////////////////////////////////////////////////////////////////
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//
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// jcmd command support for symbol table and string table dumping:
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// VM.symboltable -verbose: for dumping the symbol table
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// VM.stringtable -verbose: for dumping the string table
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//
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class VM_DumpHashtable : public VM_Operation {
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private:
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outputStream* _out;
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int _which;
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bool _verbose;
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public:
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enum {
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DumpSymbols = 1 << 0,
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DumpStrings = 1 << 1,
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DumpSysDict = 1 << 2 // not implemented yet
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};
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VM_DumpHashtable(outputStream* out, int which, bool verbose) {
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_out = out;
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_which = which;
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_verbose = verbose;
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}
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virtual VMOp_Type type() const { return VMOp_DumpHashtable; }
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virtual void doit() {
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switch (_which) {
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case DumpSymbols:
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SymbolTable::dump(_out, _verbose);
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break;
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case DumpStrings:
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StringTable::dump(_out, _verbose);
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break;
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default:
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ShouldNotReachHere();
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}
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}
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};
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class SymboltableDCmd : public DCmdWithParser {
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protected:
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DCmdArgument<bool> _verbose;
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public:
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SymboltableDCmd(outputStream* output, bool heap);
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static const char* name() {
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return "VM.symboltable";
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}
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static const char* description() {
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return "Dump symbol table.";
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}
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static const char* impact() {
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return "Medium: Depends on Java content.";
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}
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static const JavaPermission permission() {
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JavaPermission p = {"java.lang.management.ManagementPermission",
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"monitor", NULL};
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return p;
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}
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static int num_arguments();
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virtual void execute(DCmdSource source, TRAPS);
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};
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class StringtableDCmd : public DCmdWithParser {
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protected:
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DCmdArgument<bool> _verbose;
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public:
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StringtableDCmd(outputStream* output, bool heap);
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static const char* name() {
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return "VM.stringtable";
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}
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static const char* description() {
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return "Dump string table.";
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}
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static const char* impact() {
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return "Medium: Depends on Java content.";
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}
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static const JavaPermission permission() {
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JavaPermission p = {"java.lang.management.ManagementPermission",
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"monitor", NULL};
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return p;
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}
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static int num_arguments();
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virtual void execute(DCmdSource source, TRAPS);
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};
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#endif // SHARE_VM_CLASSFILE_COMPACTHASHTABLE_HPP
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