rev 60637 : 8252141: Rename G1YoungRemSetSamplingThread to better reflect its purpose
Reviewed-by:

   1 /*
   2  * Copyright (c) 2015, 2019, 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/g1CollectedHeap.inline.hpp"
  27 #include "gc/g1/g1CollectionSet.hpp"
  28 #include "gc/g1/g1ConcurrentMark.inline.hpp"
  29 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  30 #include "gc/g1/g1Policy.hpp"
  31 #include "gc/g1/g1ServiceThread.hpp"
  32 #include "gc/g1/heapRegion.inline.hpp"
  33 #include "gc/g1/heapRegionRemSet.hpp"
  34 #include "gc/shared/suspendibleThreadSet.hpp"
  35 #include "memory/universe.hpp"
  36 #include "runtime/mutexLocker.hpp"
  37 
  38 G1ServiceThread::G1ServiceThread() :
  39     ConcurrentGCThread(),
  40     _monitor(Mutex::nonleaf,
  41              "G1ServiceThread monitor",
  42              true,
  43              Monitor::_safepoint_check_never),
  44     _last_periodic_gc_attempt_s(os::elapsedTime()),
  45     _vtime_accum(0) {
  46   set_name("G1 Service");
  47   create_and_start();
  48 }
  49 
  50 void G1ServiceThread::sleep_before_next_cycle() {
  51   MonitorLocker ml(&_monitor, Mutex::_no_safepoint_check_flag);
  52   if (!should_terminate()) {
  53     uintx waitms = G1ConcRefinementServiceIntervalMillis;
  54     ml.wait(waitms);
  55   }
  56 }
  57 
  58 bool G1ServiceThread::should_start_periodic_gc() {
  59   G1CollectedHeap* g1h = G1CollectedHeap::heap();
  60   // If we are currently in a concurrent mark we are going to uncommit memory soon.
  61   if (g1h->concurrent_mark()->cm_thread()->during_cycle()) {
  62     log_debug(gc, periodic)("Concurrent cycle in progress. Skipping.");
  63     return false;
  64   }
  65 
  66   // Check if enough time has passed since the last GC.
  67   uintx time_since_last_gc = (uintx)g1h->time_since_last_collection().milliseconds();
  68   if ((time_since_last_gc < G1PeriodicGCInterval)) {
  69     log_debug(gc, periodic)("Last GC occurred " UINTX_FORMAT "ms before which is below threshold " UINTX_FORMAT "ms. Skipping.",
  70                             time_since_last_gc, G1PeriodicGCInterval);
  71     return false;
  72   }
  73 
  74   // Check if load is lower than max.
  75   double recent_load;
  76   if ((G1PeriodicGCSystemLoadThreshold > 0.0f) &&
  77       (os::loadavg(&recent_load, 1) == -1 || recent_load > G1PeriodicGCSystemLoadThreshold)) {
  78     log_debug(gc, periodic)("Load %1.2f is higher than threshold %1.2f. Skipping.",
  79                             recent_load, G1PeriodicGCSystemLoadThreshold);
  80     return false;
  81   }
  82 
  83   return true;
  84 }
  85 
  86 void G1ServiceThread::check_for_periodic_gc(){
  87   // If disabled, just return.
  88   if (G1PeriodicGCInterval == 0) {
  89     return;
  90   }
  91   if ((os::elapsedTime() - _last_periodic_gc_attempt_s) > (G1PeriodicGCInterval / 1000.0)) {
  92     log_debug(gc, periodic)("Checking for periodic GC.");
  93     if (should_start_periodic_gc()) {
  94       if (!G1CollectedHeap::heap()->try_collect(GCCause::_g1_periodic_collection)) {
  95         log_debug(gc, periodic)("GC request denied. Skipping.");
  96       }
  97     }
  98     _last_periodic_gc_attempt_s = os::elapsedTime();
  99   }
 100 }
 101 
 102 void G1ServiceThread::run_service() {
 103   double vtime_start = os::elapsedVTime();
 104 
 105   while (!should_terminate()) {
 106     sample_young_list_rs_length();
 107 
 108     if (os::supports_vtime()) {
 109       _vtime_accum = (os::elapsedVTime() - vtime_start);
 110     } else {
 111       _vtime_accum = 0.0;
 112     }
 113 
 114     check_for_periodic_gc();
 115 
 116     sleep_before_next_cycle();
 117   }
 118 }
 119 
 120 void G1ServiceThread::stop_service() {
 121   MutexLocker x(&_monitor, Mutex::_no_safepoint_check_flag);
 122   _monitor.notify();
 123 }
 124 
 125 class G1YoungRemSetSamplingClosure : public HeapRegionClosure {
 126   SuspendibleThreadSetJoiner* _sts;
 127   size_t _regions_visited;
 128   size_t _sampled_rs_length;
 129 public:
 130   G1YoungRemSetSamplingClosure(SuspendibleThreadSetJoiner* sts) :
 131     HeapRegionClosure(), _sts(sts), _regions_visited(0), _sampled_rs_length(0) { }
 132 
 133   virtual bool do_heap_region(HeapRegion* r) {
 134     size_t rs_length = r->rem_set()->occupied();
 135     _sampled_rs_length += rs_length;
 136 
 137     // Update the collection set policy information for this region
 138     G1CollectedHeap::heap()->collection_set()->update_young_region_prediction(r, rs_length);
 139 
 140     _regions_visited++;
 141 
 142     if (_regions_visited == 10) {
 143       if (_sts->should_yield()) {
 144         _sts->yield();
 145         // A gc may have occurred and our sampling data is stale and further
 146         // traversal of the collection set is unsafe
 147         return true;
 148       }
 149       _regions_visited = 0;
 150     }
 151     return false;
 152   }
 153 
 154   size_t sampled_rs_length() const { return _sampled_rs_length; }
 155 };
 156 
 157 void G1ServiceThread::sample_young_list_rs_length() {
 158   SuspendibleThreadSetJoiner sts;
 159   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 160   G1Policy* policy = g1h->policy();
 161 
 162   if (policy->use_adaptive_young_list_length()) {
 163     G1YoungRemSetSamplingClosure cl(&sts);
 164 
 165     G1CollectionSet* g1cs = g1h->collection_set();
 166     g1cs->iterate(&cl);
 167 
 168     if (cl.is_complete()) {
 169       policy->revise_young_list_target_length_if_necessary(cl.sampled_rs_length());
 170     }
 171   }
 172 }
--- EOF ---