--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/cms/freeChunk.hpp Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,151 @@
+/*
+ * Copyright (c) 2001, 2015, 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_CMS_FREECHUNK_HPP
+#define SHARE_VM_GC_CMS_FREECHUNK_HPP
+
+#include "memory/allocation.hpp"
+#include "memory/memRegion.hpp"
+#include "oops/markOop.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 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_CMS_FREECHUNK_HPP