jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp

Wed, 27 Apr 2016 01:25:04 +0800

author: aoqi
date: Wed, 27 Apr 2016 01:25:04 +0800
changeset 0: f90c822e73f8
child 6876: 710a3c8b516e
permissions: -rw-r--r--

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http://hg.openjdk.java.net/jdk8u/jdk8u/hotspot/
changeset: 6782:28b50d07f6f8
tag: jdk8u25-b17

 /*
  * Copyright (c) 2001, 2012, 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_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_FREECHUNK_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_FREECHUNK_HPP
 #include "memory/allocation.hpp"
 #include "memory/memRegion.hpp"
 #include "oops/markOop.hpp"
 #include "runtime/mutex.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 VALUE_OBJ_CLASS_SPEC {
   friend class VMStructs;
   // For 64 bit compressed oops, the markOop encodes both the size and the
   // indication that this is a FreeChunk and not an object.
   volatile size_t   _size;
   FreeChunk* _prev;
   FreeChunk* _next;
   markOop mark()     const volatile { return (markOop)_size; }
   void set_mark(markOop m)          { _size = (size_t)m; }
  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(markOopDesc::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(markOopDesc::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_VM_GC_IMPLEMENTATION_CONCURRENTMARKSWEEP_FREECHUNK_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp@f90c822e73f8 (annotated)

src/share/vm/gc_implementation/concurrentMarkSweep/freeChunk.hpp