1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp Wed Apr 27 01:25:04 2016 +0800
1.3 @@ -0,0 +1,150 @@
1.4 +/*
1.5 + * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
1.6 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
1.7 + *
1.8 + * This code is free software; you can redistribute it and/or modify it
1.9 + * under the terms of the GNU General Public License version 2 only, as
1.10 + * published by the Free Software Foundation.
1.11 + *
1.12 + * This code is distributed in the hope that it will be useful, but WITHOUT
1.13 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
1.14 + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
1.15 + * version 2 for more details (a copy is included in the LICENSE file that
1.16 + * accompanied this code).
1.17 + *
1.18 + * You should have received a copy of the GNU General Public License version
1.19 + * 2 along with this work; if not, write to the Free Software Foundation,
1.20 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
1.21 + *
1.22 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
1.23 + * or visit www.oracle.com if you need additional information or have any
1.24 + * questions.
1.25 + *
1.26 + */
1.27 +
1.28 +#ifndef SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_FREECHUNK_HPP
1.29 +#define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_FREECHUNK_HPP
1.30 +
1.31 +#include "memory/allocation.hpp"
1.32 +#include "memory/memRegion.hpp"
1.33 +#include "oops/markOop.hpp"
1.34 +#include "runtime/mutex.hpp"
1.35 +#include "utilities/debug.hpp"
1.36 +#include "utilities/globalDefinitions.hpp"
1.37 +#include "utilities/ostream.hpp"
1.38 +
1.39 +//
1.40 +// Free block maintenance for Concurrent Mark Sweep Generation
1.41 +//
1.42 +// The main data structure for free blocks are
1.43 +// . an indexed array of small free blocks, and
1.44 +// . a dictionary of large free blocks
1.45 +//
1.46 +
1.47 +// No virtuals in FreeChunk (don't want any vtables).
1.48 +
1.49 +// A FreeChunk is merely a chunk that can be in a doubly linked list
1.50 +// and has a size field. NOTE: FreeChunks are distinguished from allocated
1.51 +// objects in two ways (by the sweeper), depending on whether the VM is 32 or
1.52 +// 64 bits.
1.53 +// In 32 bits or 64 bits without CompressedOops, the second word (prev) has the
1.54 +// LSB set to indicate a free chunk; allocated objects' klass() pointers
1.55 +// don't have their LSB set. The corresponding bit in the CMSBitMap is
1.56 +// set when the chunk is allocated. There are also blocks that "look free"
1.57 +// but are not part of the free list and should not be coalesced into larger
1.58 +// free blocks. These free blocks have their two LSB's set.
1.59 +
1.60 +class FreeChunk VALUE_OBJ_CLASS_SPEC {
1.61 + friend class VMStructs;
1.62 + // For 64 bit compressed oops, the markOop encodes both the size and the
1.63 + // indication that this is a FreeChunk and not an object.
1.64 + volatile size_t _size;
1.65 + FreeChunk* _prev;
1.66 + FreeChunk* _next;
1.67 +
1.68 + markOop mark() const volatile { return (markOop)_size; }
1.69 + void set_mark(markOop m) { _size = (size_t)m; }
1.70 +
1.71 + public:
1.72 + NOT_PRODUCT(static const size_t header_size();)
1.73 +
1.74 + // Returns "true" if the address indicates that the block represents
1.75 + // a free chunk.
1.76 + static bool indicatesFreeChunk(const HeapWord* addr) {
1.77 + // Force volatile read from addr because value might change between
1.78 + // calls. We really want the read of _mark and _prev from this pointer
1.79 + // to be volatile but making the fields volatile causes all sorts of
1.80 + // compilation errors.
1.81 + return ((volatile FreeChunk*)addr)->is_free();
1.82 + }
1.83 +
1.84 + bool is_free() const volatile {
1.85 + LP64_ONLY(if (UseCompressedOops) return mark()->is_cms_free_chunk(); else)
1.86 + return (((intptr_t)_prev) & 0x1) == 0x1;
1.87 + }
1.88 + bool cantCoalesce() const {
1.89 + assert(is_free(), "can't get coalesce bit on not free");
1.90 + return (((intptr_t)_prev) & 0x2) == 0x2;
1.91 + }
1.92 + void dontCoalesce() {
1.93 + // the block should be free
1.94 + assert(is_free(), "Should look like a free block");
1.95 + _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2);
1.96 + }
1.97 + FreeChunk* prev() const {
1.98 + return (FreeChunk*)(((intptr_t)_prev) & ~(0x3));
1.99 + }
1.100 +
1.101 + debug_only(void* prev_addr() const { return (void*)&_prev; })
1.102 + debug_only(void* next_addr() const { return (void*)&_next; })
1.103 + debug_only(void* size_addr() const { return (void*)&_size; })
1.104 +
1.105 + size_t size() const volatile {
1.106 + LP64_ONLY(if (UseCompressedOops) return mark()->get_size(); else )
1.107 + return _size;
1.108 + }
1.109 + void set_size(size_t sz) {
1.110 + LP64_ONLY(if (UseCompressedOops) set_mark(markOopDesc::set_size_and_free(sz)); else )
1.111 + _size = sz;
1.112 + }
1.113 +
1.114 + FreeChunk* next() const { return _next; }
1.115 +
1.116 + void link_after(FreeChunk* ptr) {
1.117 + link_next(ptr);
1.118 + if (ptr != NULL) ptr->link_prev(this);
1.119 + }
1.120 + void link_next(FreeChunk* ptr) { _next = ptr; }
1.121 + void link_prev(FreeChunk* ptr) {
1.122 + LP64_ONLY(if (UseCompressedOops) _prev = ptr; else)
1.123 + _prev = (FreeChunk*)((intptr_t)ptr | 0x1);
1.124 + }
1.125 + void clear_next() { _next = NULL; }
1.126 + void markNotFree() {
1.127 + // Set _prev (klass) to null before (if) clearing the mark word below
1.128 + _prev = NULL;
1.129 +#ifdef _LP64
1.130 + if (UseCompressedOops) {
1.131 + OrderAccess::storestore();
1.132 + set_mark(markOopDesc::prototype());
1.133 + }
1.134 +#endif
1.135 + assert(!is_free(), "Error");
1.136 + }
1.137 +
1.138 + // Return the address past the end of this chunk
1.139 + uintptr_t* end() const { return ((uintptr_t*) this) + size(); }
1.140 +
1.141 + // debugging
1.142 + void verify() const PRODUCT_RETURN;
1.143 + void verifyList() const PRODUCT_RETURN;
1.144 + void mangleAllocated(size_t size) PRODUCT_RETURN;
1.145 + void mangleFreed(size_t size) PRODUCT_RETURN;
1.146 +
1.147 + void print_on(outputStream* st);
1.148 +};
1.149 +
1.150 +extern size_t MinChunkSize;
1.151 +
1.152 +
1.153 +#endif // SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_FREECHUNK_HPP
