hotspot/src/share/vm/gc/g1/vm_operations_g1.cpp
changeset 30764 fec48bf5a827
parent 30147 af9a41999c6e
child 31032 8e72621ca186
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/g1/vm_operations_g1.cpp	Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,251 @@
+/*
+ * 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc/g1/concurrentMarkThread.inline.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "gc/g1/g1CollectorPolicy.hpp"
+#include "gc/g1/g1Log.hpp"
+#include "gc/g1/vm_operations_g1.hpp"
+#include "gc/shared/gcTimer.hpp"
+#include "gc/shared/gcTraceTime.hpp"
+#include "gc/shared/isGCActiveMark.hpp"
+#include "runtime/interfaceSupport.hpp"
+
+VM_G1CollectForAllocation::VM_G1CollectForAllocation(uint 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 with this operation.");
+}
+
+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(uint           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_G1OperationWithAllocRequest::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 || g1h->should_do_concurrent_full_gc(_gc_cause),
+      "only a GC locker, a System.gc(), stats update, whitebox, 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_G1OperationWithAllocRequest::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.
+  SurrogateLockerThread* slt = ConcurrentMarkThread::slt();
+  if (slt != NULL) {
+    slt->manipulatePLL(SurrogateLockerThread::acquirePLL);
+  } else {
+    SurrogateLockerThread::report_missing_slt();
+  }
+}
+
+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() {
+  TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
+  G1CollectedHeap* g1h = G1CollectedHeap::heap();
+  GCTraceTime t(_printGCMessage, G1Log::fine(), true, g1h->gc_timer_cm(), g1h->concurrent_mark()->concurrent_gc_id());
+  IsGCActiveMark x;
+  _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();
+  return true;
+}
+
+void VM_CGC_Operation::doit_epilogue() {
+  // Note the relative order of the unlocks must match that in
+  // VM_GC_Operation::doit_epilogue()
+  Heap_lock->unlock();
+  if (_needs_pll) {
+    release_and_notify_pending_list_lock();
+  }
+}