src/share/vm/gc_implementation/g1/vm_operations_g1.cpp

Mon, 28 Jun 2010 14:13:17 -0400

author
tonyp
date
Mon, 28 Jun 2010 14:13:17 -0400
changeset 2011
4e5661ba9d98
parent 1907
c18cbe5936b8
child 2314
f95d63e2154a
permissions
-rw-r--r--

6944166: G1: explicit GCs are not always handled correctly
Summary: G1 was not handling explicit GCs correctly in many ways. It does now. See the CR for the list of improvements contained in this changeset.
Reviewed-by: iveresov, ysr, johnc

     1 /*
     2  * Copyright (c) 2001, 2009, Oracle and/or its affiliates. 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
    16  * 2 along with this work; if not, write to the Free Software Foundation,
    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
    18  *
    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
    20  * or visit www.oracle.com if you need additional information or have any
    21  * questions.
    22  *
    23  */
    25 #include "incls/_precompiled.incl"
    26 #include "incls/_vm_operations_g1.cpp.incl"
    28 void VM_G1CollectForAllocation::doit() {
    29   JvmtiGCForAllocationMarker jgcm;
    30   G1CollectedHeap* g1h = G1CollectedHeap::heap();
    31   _res = g1h->satisfy_failed_allocation(_size);
    32   assert(g1h->is_in_or_null(_res), "result not in heap");
    33 }
    35 void VM_G1CollectFull::doit() {
    36   JvmtiGCFullMarker jgcm;
    37   G1CollectedHeap* g1h = G1CollectedHeap::heap();
    38   GCCauseSetter x(g1h, _gc_cause);
    39   g1h->do_full_collection(false /* clear_all_soft_refs */);
    40 }
    42 void VM_G1IncCollectionPause::doit() {
    43   JvmtiGCForAllocationMarker jgcm;
    44   G1CollectedHeap* g1h = G1CollectedHeap::heap();
    45   assert(!_should_initiate_conc_mark ||
    46   ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
    47    (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent)),
    48          "only a GC locker or a System.gc() induced GC should start a cycle");
    50   GCCauseSetter x(g1h, _gc_cause);
    51   if (_should_initiate_conc_mark) {
    52     // It's safer to read full_collections_completed() here, given
    53     // that noone else will be updating it concurrently. Since we'll
    54     // only need it if we're initiating a marking cycle, no point in
    55     // setting it earlier.
    56     _full_collections_completed_before = g1h->full_collections_completed();
    58     // At this point we are supposed to start a concurrent cycle. We
    59     // will do so if one is not already in progress.
    60     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle();
    61   }
    62   g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
    63 }
    65 void VM_G1IncCollectionPause::doit_epilogue() {
    66   VM_GC_Operation::doit_epilogue();
    68   // If the pause was initiated by a System.gc() and
    69   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
    70   // that just started (or maybe one that was already in progress) to
    71   // finish.
    72   if (_gc_cause == GCCause::_java_lang_system_gc &&
    73       _should_initiate_conc_mark) {
    74     assert(ExplicitGCInvokesConcurrent,
    75            "the only way to be here is if ExplicitGCInvokesConcurrent is set");
    77     G1CollectedHeap* g1h = G1CollectedHeap::heap();
    79     // In the doit() method we saved g1h->full_collections_completed()
    80     // in the _full_collections_completed_before field. We have to
    81     // wait until we observe that g1h->full_collections_completed()
    82     // has increased by at least one. This can happen if a) we started
    83     // a cycle and it completes, b) a cycle already in progress
    84     // completes, or c) a Full GC happens.
    86     // If the condition has already been reached, there's no point in
    87     // actually taking the lock and doing the wait.
    88     if (g1h->full_collections_completed() <=
    89                                           _full_collections_completed_before) {
    90       // The following is largely copied from CMS
    92       Thread* thr = Thread::current();
    93       assert(thr->is_Java_thread(), "invariant");
    94       JavaThread* jt = (JavaThread*)thr;
    95       ThreadToNativeFromVM native(jt);
    97       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
    98       while (g1h->full_collections_completed() <=
    99                                           _full_collections_completed_before) {
   100         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
   101       }
   102     }
   103   }
   104 }
   106 void VM_CGC_Operation::doit() {
   107   gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
   108   TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
   109   TraceTime t(_printGCMessage, PrintGC, true, gclog_or_tty);
   110   SharedHeap* sh = SharedHeap::heap();
   111   // This could go away if CollectedHeap gave access to _gc_is_active...
   112   if (sh != NULL) {
   113     IsGCActiveMark x;
   114     _cl->do_void();
   115   } else {
   116     _cl->do_void();
   117   }
   118 }
   120 bool VM_CGC_Operation::doit_prologue() {
   121   Heap_lock->lock();
   122   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
   123   return true;
   124 }
   126 void VM_CGC_Operation::doit_epilogue() {
   127   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
   128   Heap_lock->unlock();
   129 }

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