diff -r f0312c7d5b37 -r ba6c248cae19 src/hotspot/share/gc/cms/freeChunk.hpp --- a/src/hotspot/share/gc/cms/freeChunk.hpp Wed Nov 13 11:21:15 2019 +0100 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,150 +0,0 @@ -/* - * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved. - * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. - * - * This code is free software; you can redistribute it and/or modify it - * under the terms of the GNU General Public License version 2 only, as - * published by the Free Software Foundation. - * - * This code is distributed in the hope that it will be useful, but WITHOUT - * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or - * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License - * version 2 for more details (a copy is included in the LICENSE file that - * accompanied this code). - * - * You should have received a copy of the GNU General Public License version - * 2 along with this work; if not, write to the Free Software Foundation, - * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. - * - * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA - * or visit www.oracle.com if you need additional information or have any - * questions. - * - */ - -#ifndef SHARE_GC_CMS_FREECHUNK_HPP -#define SHARE_GC_CMS_FREECHUNK_HPP - -#include "memory/memRegion.hpp" -#include "oops/markWord.hpp" -#include "runtime/mutex.hpp" -#include "runtime/orderAccess.hpp" -#include "utilities/debug.hpp" -#include "utilities/globalDefinitions.hpp" -#include "utilities/ostream.hpp" - -// -// Free block maintenance for Concurrent Mark Sweep Generation -// -// The main data structure for free blocks are -// . an indexed array of small free blocks, and -// . a dictionary of large free blocks -// - -// No virtuals in FreeChunk (don't want any vtables). - -// A FreeChunk is merely a chunk that can be in a doubly linked list -// and has a size field. NOTE: FreeChunks are distinguished from allocated -// objects in two ways (by the sweeper), depending on whether the VM is 32 or -// 64 bits. -// In 32 bits or 64 bits without CompressedOops, the second word (prev) has the -// LSB set to indicate a free chunk; allocated objects' klass() pointers -// don't have their LSB set. The corresponding bit in the CMSBitMap is -// set when the chunk is allocated. There are also blocks that "look free" -// but are not part of the free list and should not be coalesced into larger -// free blocks. These free blocks have their two LSB's set. - -class FreeChunk { - friend class VMStructs; - // For 64 bit compressed oops, the markWord encodes both the size and the - // indication that this is a FreeChunk and not an object. - volatile size_t _size; - FreeChunk* _prev; - FreeChunk* _next; - - markWord mark() const volatile { return markWord((uintptr_t)_size); } - void set_mark(markWord m) { _size = (size_t)m.value(); } - - public: - NOT_PRODUCT(static const size_t header_size();) - - // Returns "true" if the address indicates that the block represents - // a free chunk. - static bool indicatesFreeChunk(const HeapWord* addr) { - // Force volatile read from addr because value might change between - // calls. We really want the read of _mark and _prev from this pointer - // to be volatile but making the fields volatile causes all sorts of - // compilation errors. - return ((volatile FreeChunk*)addr)->is_free(); - } - - bool is_free() const volatile { - LP64_ONLY(if (UseCompressedOops) return mark().is_cms_free_chunk(); else) - return (((intptr_t)_prev) & 0x1) == 0x1; - } - bool cantCoalesce() const { - assert(is_free(), "can't get coalesce bit on not free"); - return (((intptr_t)_prev) & 0x2) == 0x2; - } - void dontCoalesce() { - // the block should be free - assert(is_free(), "Should look like a free block"); - _prev = (FreeChunk*)(((intptr_t)_prev) | 0x2); - } - FreeChunk* prev() const { - return (FreeChunk*)(((intptr_t)_prev) & ~(0x3)); - } - - debug_only(void* prev_addr() const { return (void*)&_prev; }) - debug_only(void* next_addr() const { return (void*)&_next; }) - debug_only(void* size_addr() const { return (void*)&_size; }) - - size_t size() const volatile { - LP64_ONLY(if (UseCompressedOops) return mark().get_size(); else ) - return _size; - } - void set_size(size_t sz) { - LP64_ONLY(if (UseCompressedOops) set_mark(markWord::set_size_and_free(sz)); else ) - _size = sz; - } - - FreeChunk* next() const { return _next; } - - void link_after(FreeChunk* ptr) { - link_next(ptr); - if (ptr != NULL) ptr->link_prev(this); - } - void link_next(FreeChunk* ptr) { _next = ptr; } - void link_prev(FreeChunk* ptr) { - LP64_ONLY(if (UseCompressedOops) _prev = ptr; else) - _prev = (FreeChunk*)((intptr_t)ptr | 0x1); - } - void clear_next() { _next = NULL; } - void markNotFree() { - // Set _prev (klass) to null before (if) clearing the mark word below - _prev = NULL; -#ifdef _LP64 - if (UseCompressedOops) { - OrderAccess::storestore(); - set_mark(markWord::prototype()); - } -#endif - assert(!is_free(), "Error"); - } - - // Return the address past the end of this chunk - uintptr_t* end() const { return ((uintptr_t*) this) + size(); } - - // debugging - void verify() const PRODUCT_RETURN; - void verifyList() const PRODUCT_RETURN; - void mangleAllocated(size_t size) PRODUCT_RETURN; - void mangleFreed(size_t size) PRODUCT_RETURN; - - void print_on(outputStream* st); -}; - -extern size_t MinChunkSize; - - -#endif // SHARE_GC_CMS_FREECHUNK_HPP