jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/vm_operations

src/share/vm/gc_implementation/g1/vm_operations_g1.cpp@e7d0505c8a30 (annotated)

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

Fri, 10 Oct 2014 15:51:58 +0200

author: tschatzl
date: Fri, 10 Oct 2014 15:51:58 +0200
changeset 7257: e7d0505c8a30
parent 7236: d3fd73295885
child 7360: 4e4ebe50c8e3
permissions: -rw-r--r--

8059758: Footprint regressions with JDK-8038423
Summary: Changes in JDK-8038423 always initialize (zero out) virtual memory used for auxiliary data structures. This causes a footprint regression for G1 in startup benchmarks. This is because they do not touch that memory at all, so the operating system does not actually commit these pages. The fix is to, if the initialization value of the data structures matches the default value of just committed memory (=0), do not do anything.
Reviewed-by: jwilhelm, brutisso

 /*
  * Copyright (c) 2001, 2013, 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.
  *
  */
 #include "precompiled.hpp"
 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
 #include "gc_implementation/g1/g1Log.hpp"
 #include "gc_implementation/g1/vm_operations_g1.hpp"
 #include "gc_implementation/shared/gcTimer.hpp"
 #include "gc_implementation/shared/gcTraceTime.hpp"
 #include "gc_implementation/shared/isGCActiveMark.hpp"
 #include "gc_implementation/g1/vm_operations_g1.hpp"
 #include "runtime/interfaceSupport.hpp"
 VM_G1CollectForAllocation::VM_G1CollectForAllocation(
                                                   unsigned int gc_count_before,
                                                   size_t word_size)
   : VM_G1OperationWithAllocRequest(gc_count_before, word_size,
                                    GCCause::_allocation_failure) {
   guarantee(word_size > 0, "an allocation should always be requested");
 }
 void VM_G1CollectForAllocation::doit() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   GCCauseSetter x(g1h, _gc_cause);
   _result = g1h->satisfy_failed_allocation(_word_size, allocation_context(), &_pause_succeeded);
   assert(_result == NULL || _pause_succeeded,
          "if we get back a result, the pause should have succeeded");
 }
 void VM_G1CollectFull::doit() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   GCCauseSetter x(g1h, _gc_cause);
   g1h->do_full_collection(false /* clear_all_soft_refs */);
 }
 VM_G1IncCollectionPause::VM_G1IncCollectionPause(
                                       unsigned int   gc_count_before,
                                       size_t         word_size,
                                       bool           should_initiate_conc_mark,
                                       double         target_pause_time_ms,
                                       GCCause::Cause gc_cause)
   : VM_G1OperationWithAllocRequest(gc_count_before, word_size, gc_cause),
     _should_initiate_conc_mark(should_initiate_conc_mark),
     _target_pause_time_ms(target_pause_time_ms),
     _should_retry_gc(false),
     _old_marking_cycles_completed_before(0) {
   guarantee(target_pause_time_ms > 0.0,
             err_msg("target_pause_time_ms = %1.6lf should be positive",
                     target_pause_time_ms));
   _gc_cause = gc_cause;
 }
 bool VM_G1IncCollectionPause::doit_prologue() {
   bool res = VM_GC_Operation::doit_prologue();
   if (!res) {
     if (_should_initiate_conc_mark) {
       // The prologue can fail for a couple of reasons. The first is that another GC
       // got scheduled and prevented the scheduling of the initial mark GC. The
       // second is that the GC locker may be active and the heap can't be expanded.
       // In both cases we want to retry the GC so that the initial mark pause is
       // actually scheduled. In the second case, however, we should stall until
       // until the GC locker is no longer active and then retry the initial mark GC.
       _should_retry_gc = true;
     }
   }
   return res;
 }
 void VM_G1IncCollectionPause::doit() {
   G1CollectedHeap* g1h = G1CollectedHeap::heap();
   assert(!_should_initiate_conc_mark ||
   ((_gc_cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
    (_gc_cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent) ||
     _gc_cause == GCCause::_g1_humongous_allocation ||
     _gc_cause == GCCause::_update_allocation_context_stats_inc),
       "only a GC locker, a System.gc(), stats update or a hum allocation induced GC should start a cycle");
   if (_word_size > 0) {
     // An allocation has been requested. So, try to do that first.
     _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
                                      false /* expect_null_cur_alloc_region */);
     if (_result != NULL) {
       // If we can successfully allocate before we actually do the
       // pause then we will consider this pause successful.
       _pause_succeeded = true;
       return;
     }
   }
   GCCauseSetter x(g1h, _gc_cause);
   if (_should_initiate_conc_mark) {
     // It's safer to read old_marking_cycles_completed() here, given
     // that noone else will be updating it concurrently. Since we'll
     // only need it if we're initiating a marking cycle, no point in
     // setting it earlier.
     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
     // At this point we are supposed to start a concurrent cycle. We
     // will do so if one is not already in progress.
     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
     // The above routine returns true if we were able to force the
     // next GC pause to be an initial mark; it returns false if a
     // marking cycle is already in progress.
     //
     // If a marking cycle is already in progress just return and skip the
     // pause below - if the reason for requesting this initial mark pause
     // was due to a System.gc() then the requesting thread should block in
     // doit_epilogue() until the marking cycle is complete.
     //
     // If this initial mark pause was requested as part of a humongous
     // allocation then we know that the marking cycle must just have
     // been started by another thread (possibly also allocating a humongous
     // object) as there was no active marking cycle when the requesting
     // thread checked before calling collect() in
     // attempt_allocation_humongous(). Retrying the GC, in this case,
     // will cause the requesting thread to spin inside collect() until the
     // just started marking cycle is complete - which may be a while. So
     // we do NOT retry the GC.
     if (!res) {
       assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
       if (_gc_cause != GCCause::_g1_humongous_allocation) {
         _should_retry_gc = true;
       }
       return;
     }
   }
   _pause_succeeded =
     g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
   if (_pause_succeeded && _word_size > 0) {
     // An allocation had been requested.
     _result = g1h->attempt_allocation_at_safepoint(_word_size, allocation_context(),
                                       true /* expect_null_cur_alloc_region */);
   } else {
     assert(_result == NULL, "invariant");
     if (!_pause_succeeded) {
       // Another possible reason reason for the pause to not be successful
       // is that, again, the GC locker is active (and has become active
       // since the prologue was executed). In this case we should retry
       // the pause after waiting for the GC locker to become inactive.
       _should_retry_gc = true;
     }
   }
 }
 void VM_G1IncCollectionPause::doit_epilogue() {
   VM_GC_Operation::doit_epilogue();
   // If the pause was initiated by a System.gc() and
   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
   // that just started (or maybe one that was already in progress) to
   // finish.
   if (_gc_cause == GCCause::_java_lang_system_gc &&
       _should_initiate_conc_mark) {
     assert(ExplicitGCInvokesConcurrent,
            "the only way to be here is if ExplicitGCInvokesConcurrent is set");
     G1CollectedHeap* g1h = G1CollectedHeap::heap();
     // In the doit() method we saved g1h->old_marking_cycles_completed()
     // in the _old_marking_cycles_completed_before field. We have to
     // wait until we observe that g1h->old_marking_cycles_completed()
     // has increased by at least one. This can happen if a) we started
     // a cycle and it completes, b) a cycle already in progress
     // completes, or c) a Full GC happens.
     // If the condition has already been reached, there's no point in
     // actually taking the lock and doing the wait.
     if (g1h->old_marking_cycles_completed() <=
                                           _old_marking_cycles_completed_before) {
       // The following is largely copied from CMS
       Thread* thr = Thread::current();
       assert(thr->is_Java_thread(), "invariant");
       JavaThread* jt = (JavaThread*)thr;
       ThreadToNativeFromVM native(jt);
       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
       while (g1h->old_marking_cycles_completed() <=
                                           _old_marking_cycles_completed_before) {
         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
       }
     }
   }
 }
 void VM_CGC_Operation::acquire_pending_list_lock() {
   assert(_needs_pll, "don't call this otherwise");
   // The caller may block while communicating
   // with the SLT thread in order to acquire/release the PLL.
   ConcurrentMarkThread::slt()->
     manipulatePLL(SurrogateLockerThread::acquirePLL);
 }
 void VM_CGC_Operation::release_and_notify_pending_list_lock() {
   assert(_needs_pll, "don't call this otherwise");
   // The caller may block while communicating
   // with the SLT thread in order to acquire/release the PLL.
   ConcurrentMarkThread::slt()->
     manipulatePLL(SurrogateLockerThread::releaseAndNotifyPLL);
 }
 void VM_CGC_Operation::doit() {
   gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
   TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
   GCTraceTime t(_printGCMessage, G1Log::fine(), true, G1CollectedHeap::heap()->gc_timer_cm(), G1CollectedHeap::heap()->concurrent_mark()->concurrent_gc_id());
   SharedHeap* sh = SharedHeap::heap();
   // This could go away if CollectedHeap gave access to _gc_is_active...
   if (sh != NULL) {
     IsGCActiveMark x;
     _cl->do_void();
   } else {
     _cl->do_void();
   }
 }
 bool VM_CGC_Operation::doit_prologue() {
   // Note the relative order of the locks must match that in
   // VM_GC_Operation::doit_prologue() or deadlocks can occur
   if (_needs_pll) {
     acquire_pending_list_lock();
   }
   Heap_lock->lock();
   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = true;
   return true;
 }
 void VM_CGC_Operation::doit_epilogue() {
   // Note the relative order of the unlocks must match that in
   // VM_GC_Operation::doit_epilogue()
   SharedHeap::heap()->_thread_holds_heap_lock_for_gc = false;
   Heap_lock->unlock();
   if (_needs_pll) {
     release_and_notify_pending_list_lock();
   }
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/vm_operations_g1.cpp@e7d0505c8a30 (annotated)

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