jdk8-mips64-public/hotspot: src/share/vm/memory/referencePolicy.cpp@c96030fff130

6684579: SoftReference processing can be made more efficient
Summary: For current soft-ref clearing policies, we can decide at marking time if a soft-reference will definitely not be cleared, postponing the decision of whether it will definitely be cleared to the final reference processing phase. This can be especially beneficial in the case of concurrent collectors where the marking is usually concurrent but reference processing is usually not.
Reviewed-by: jmasa

     1 /*

     2  * Copyright 2000-2003 Sun Microsystems, Inc.  All Rights Reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

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    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

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    23  */

    25 # include "incls/_precompiled.incl"

    26 # include "incls/_referencePolicy.cpp.incl"

    28 LRUCurrentHeapPolicy::LRUCurrentHeapPolicy() {

    29   snap();

    30 }

    32 // Capture state (of-the-VM) information needed to evaluate the policy

    33 void LRUCurrentHeapPolicy::snap() {

    34   _max_interval = (Universe::get_heap_free_at_last_gc() / M) * SoftRefLRUPolicyMSPerMB;

    35   assert(_max_interval >= 0,"Sanity check");

    36 }

    38 // The oop passed in is the SoftReference object, and not

    39 // the object the SoftReference points to.

    40 bool LRUCurrentHeapPolicy::should_clear_reference(oop p) {

    41   jlong interval = java_lang_ref_SoftReference::clock() - java_lang_ref_SoftReference::timestamp(p);

    42   assert(interval >= 0, "Sanity check");

    44   // The interval will be zero if the ref was accessed since the last scavenge/gc.

    45   if(interval <= _max_interval) {

    46     return false;

    47   }

    49   return true;

    50 }

    52 /////////////////////// MaxHeap //////////////////////

    54 LRUMaxHeapPolicy::LRUMaxHeapPolicy() {

    55   snap();

    56 }

    58 // Capture state (of-the-VM) information needed to evaluate the policy

    59 void LRUMaxHeapPolicy::snap() {

    60   size_t max_heap = MaxHeapSize;

    61   max_heap -= Universe::get_heap_used_at_last_gc();

    62   max_heap /= M;

    64   _max_interval = max_heap * SoftRefLRUPolicyMSPerMB;

    65   assert(_max_interval >= 0,"Sanity check");

    66 }

    68 // The oop passed in is the SoftReference object, and not

    69 // the object the SoftReference points to.

    70 bool LRUMaxHeapPolicy::should_clear_reference(oop p) {

    71   jlong interval = java_lang_ref_SoftReference::clock() - java_lang_ref_SoftReference::timestamp(p);

    72   assert(interval >= 0, "Sanity check");

    74   // The interval will be zero if the ref was accessed since the last scavenge/gc.

    75   if(interval <= _max_interval) {

    76     return false;

    77   }

    79   return true;

    80 }

Mercurial > jdk8-mips64-public > hotspot / file revision

src/share/vm/memory/referencePolicy.cpp@c96030fff130

src/share/vm/memory/referencePolicy.cpp