1 /*
   2  * Copyright (c) 2001, 2018, 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  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/g1/concurrentMarkThread.inline.hpp"
  27 #include "gc/g1/g1CollectedHeap.inline.hpp"
  28 #include "gc/g1/g1Policy.hpp"
  29 #include "gc/shared/gcId.hpp"
  30 #include "gc/g1/vm_operations_g1.hpp"
  31 #include "gc/shared/gcTimer.hpp"
  32 #include "gc/shared/gcTraceTime.inline.hpp"
  33 #include "gc/shared/isGCActiveMark.hpp"
  34 #include "runtime/interfaceSupport.inline.hpp"
  35 
  36 void VM_G1CollectFull::doit() {
  37   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  38   GCCauseSetter x(g1h, _gc_cause);
  39   g1h->do_full_collection(false /* clear_all_soft_refs */);
  40 }
  41 
  42 VM_G1CollectForAllocation::VM_G1CollectForAllocation(size_t         word_size,
  43                                                      uint           gc_count_before,
  44                                                      GCCause::Cause gc_cause,
  45                                                      bool           should_initiate_conc_mark,
  46                                                      double         target_pause_time_ms)
  47   : VM_CollectForAllocation(word_size, gc_count_before, gc_cause),
  48     _pause_succeeded(false),
  49     _should_initiate_conc_mark(should_initiate_conc_mark),
  50     _target_pause_time_ms(target_pause_time_ms),
  51     _should_retry_gc(false),
  52     _old_marking_cycles_completed_before(0) {
  53   guarantee(target_pause_time_ms > 0.0,
  54             "target_pause_time_ms = %1.6lf should be positive",
  55             target_pause_time_ms);
  56   _gc_cause = gc_cause;
  57 }
  58 
  59 bool VM_G1CollectForAllocation::doit_prologue() {
  60   bool res = VM_CollectForAllocation::doit_prologue();
  61   if (!res) {
  62     if (_should_initiate_conc_mark) {
  63       // The prologue can fail for a couple of reasons. The first is that another GC
  64       // got scheduled and prevented the scheduling of the initial mark GC. The
  65       // second is that the GC locker may be active and the heap can't be expanded.
  66       // In both cases we want to retry the GC so that the initial mark pause is
  67       // actually scheduled. In the second case, however, we should stall until
  68       // until the GC locker is no longer active and then retry the initial mark GC.
  69       _should_retry_gc = true;
  70     }
  71   }
  72   return res;
  73 }
  74 
  75 void VM_G1CollectForAllocation::doit() {
  76   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  77   assert(!_should_initiate_conc_mark || g1h->should_do_concurrent_full_gc(_gc_cause),
  78       "only a GC locker, a System.gc(), stats update, whitebox, or a hum allocation induced GC should start a cycle");
  79 
  80   if (_word_size > 0) {
  81     // An allocation has been requested. So, try to do that first.
  82     _result = g1h->attempt_allocation_at_safepoint(_word_size,
  83                                                    false /* expect_null_cur_alloc_region */);
  84     if (_result != NULL) {
  85       // If we can successfully allocate before we actually do the
  86       // pause then we will consider this pause successful.
  87       _pause_succeeded = true;
  88       return;
  89     }
  90   }
  91 
  92   GCCauseSetter x(g1h, _gc_cause);
  93   if (_should_initiate_conc_mark) {
  94     // It's safer to read old_marking_cycles_completed() here, given
  95     // that noone else will be updating it concurrently. Since we'll
  96     // only need it if we're initiating a marking cycle, no point in
  97     // setting it earlier.
  98     _old_marking_cycles_completed_before = g1h->old_marking_cycles_completed();
  99 
 100     // At this point we are supposed to start a concurrent cycle. We
 101     // will do so if one is not already in progress.
 102     bool res = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
 103 
 104     // The above routine returns true if we were able to force the
 105     // next GC pause to be an initial mark; it returns false if a
 106     // marking cycle is already in progress.
 107     //
 108     // If a marking cycle is already in progress just return and skip the
 109     // pause below - if the reason for requesting this initial mark pause
 110     // was due to a System.gc() then the requesting thread should block in
 111     // doit_epilogue() until the marking cycle is complete.
 112     //
 113     // If this initial mark pause was requested as part of a humongous
 114     // allocation then we know that the marking cycle must just have
 115     // been started by another thread (possibly also allocating a humongous
 116     // object) as there was no active marking cycle when the requesting
 117     // thread checked before calling collect() in
 118     // attempt_allocation_humongous(). Retrying the GC, in this case,
 119     // will cause the requesting thread to spin inside collect() until the
 120     // just started marking cycle is complete - which may be a while. So
 121     // we do NOT retry the GC.
 122     if (!res) {
 123       assert(_word_size == 0, "Concurrent Full GC/Humongous Object IM shouldn't be allocating");
 124       if (_gc_cause != GCCause::_g1_humongous_allocation) {
 125         _should_retry_gc = true;
 126       }
 127       return;
 128     }
 129   }
 130 
 131   // Try a partial collection of some kind.
 132   _pause_succeeded = g1h->do_collection_pause_at_safepoint(_target_pause_time_ms);
 133 
 134   if (_pause_succeeded) {
 135     if (_word_size > 0) {
 136       // An allocation had been requested. Do it, eventually trying a stronger
 137       // kind of GC.
 138       _result = g1h->satisfy_failed_allocation(_word_size, &_pause_succeeded);
 139     } else {
 140       bool should_upgrade_to_full = !g1h->should_do_concurrent_full_gc(_gc_cause) &&
 141                                     !g1h->has_regions_left_for_allocation();
 142       if (should_upgrade_to_full) {
 143         // There has been a request to perform a GC to free some space. We have no
 144         // information on how much memory has been asked for. In case there are
 145         // absolutely no regions left to allocate into, do a maximally compacting full GC.
 146         log_info(gc, ergo)("Attempting maximally compacting collection");
 147         _pause_succeeded = g1h->do_full_collection(false, /* explicit gc */
 148                                                    true   /* clear_all_soft_refs */);
 149       }
 150     }
 151     guarantee(_pause_succeeded, "Elevated collections during the safepoint must always succeed.");
 152   } else {
 153     assert(_result == NULL, "invariant");
 154     // The only reason for the pause to not be successful is that, the GC locker is
 155     // active (or has become active since the prologue was executed). In this case
 156     // we should retry the pause after waiting for the GC locker to become inactive.
 157     _should_retry_gc = true;
 158   }
 159 }
 160 
 161 void VM_G1CollectForAllocation::doit_epilogue() {
 162   VM_CollectForAllocation::doit_epilogue();
 163 
 164   // If the pause was initiated by a System.gc() and
 165   // +ExplicitGCInvokesConcurrent, we have to wait here for the cycle
 166   // that just started (or maybe one that was already in progress) to
 167   // finish.
 168   if (GCCause::is_user_requested_gc(_gc_cause) &&
 169       _should_initiate_conc_mark) {
 170     assert(ExplicitGCInvokesConcurrent,
 171            "the only way to be here is if ExplicitGCInvokesConcurrent is set");
 172 
 173     G1CollectedHeap* g1h = G1CollectedHeap::heap();
 174 
 175     // In the doit() method we saved g1h->old_marking_cycles_completed()
 176     // in the _old_marking_cycles_completed_before field. We have to
 177     // wait until we observe that g1h->old_marking_cycles_completed()
 178     // has increased by at least one. This can happen if a) we started
 179     // a cycle and it completes, b) a cycle already in progress
 180     // completes, or c) a Full GC happens.
 181 
 182     // If the condition has already been reached, there's no point in
 183     // actually taking the lock and doing the wait.
 184     if (g1h->old_marking_cycles_completed() <=
 185                                           _old_marking_cycles_completed_before) {
 186       // The following is largely copied from CMS
 187 
 188       Thread* thr = Thread::current();
 189       assert(thr->is_Java_thread(), "invariant");
 190       JavaThread* jt = (JavaThread*)thr;
 191       ThreadToNativeFromVM native(jt);
 192 
 193       MutexLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
 194       while (g1h->old_marking_cycles_completed() <=
 195                                           _old_marking_cycles_completed_before) {
 196         FullGCCount_lock->wait(Mutex::_no_safepoint_check_flag);
 197       }
 198     }
 199   }
 200 }
 201 
 202 void VM_CGC_Operation::doit() {
 203   GCIdMark gc_id_mark(_gc_id);
 204   GCTraceCPUTime tcpu;
 205   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 206   GCTraceTime(Info, gc) t(_printGCMessage, g1h->concurrent_mark()->gc_timer_cm(), GCCause::_no_gc, true);
 207   TraceCollectorStats tcs(g1h->g1mm()->conc_collection_counters());
 208   SvcGCMarker sgcm(SvcGCMarker::CONCURRENT);
 209   IsGCActiveMark x;
 210   _cl->do_void();
 211 }
 212 
 213 bool VM_CGC_Operation::doit_prologue() {
 214   Heap_lock->lock();
 215   return true;
 216 }
 217 
 218 void VM_CGC_Operation::doit_epilogue() {
 219   if (Universe::has_reference_pending_list()) {
 220     Heap_lock->notify_all();
 221   }
 222   Heap_lock->unlock();
 223 }
--- EOF ---