1 /*
  2  * Copyright Amazon.com Inc. 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 #include "precompiled.hpp"
 25 
 26 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
 27 #include "gc/shenandoah/mode/shenandoahMode.hpp"
 28 #include "gc/shenandoah/shenandoahAsserts.hpp"
 29 #include "gc/shenandoah/shenandoahGenerationalControlThread.hpp"
 30 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 31 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
 32 #include "gc/shenandoah/shenandoahRegulatorThread.hpp"
 33 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
 34 #include "logging/log.hpp"
 35 
 36 ShenandoahRegulatorThread::ShenandoahRegulatorThread(ShenandoahGenerationalControlThread* control_thread) :
 37   ConcurrentGCThread(),
 38   _control_thread(control_thread),
 39   _sleep(ShenandoahControlIntervalMin),
 40   _last_sleep_adjust_time(os::elapsedTime()) {
 41   shenandoah_assert_generational();
 42   ShenandoahHeap* heap = ShenandoahHeap::heap();
 43   _old_heuristics = heap->old_generation()->heuristics();
 44   _young_heuristics = heap->young_generation()->heuristics();
 45   _global_heuristics = heap->global_generation()->heuristics();
 46 
 47   set_name("Shenandoah Regulator Thread");
 48   create_and_start();
 49 }
 50 
 51 void ShenandoahRegulatorThread::run_service() {
 52   if (ShenandoahAllowOldMarkingPreemption) {
 53     regulate_young_and_old_cycles();
 54   } else {
 55     regulate_young_and_global_cycles();
 56   }
 57 
 58   log_info(gc)("%s: Done.", name());
 59 }
 60 
 61 void ShenandoahRegulatorThread::regulate_young_and_old_cycles() {
 62   while (!should_terminate()) {
 63     ShenandoahGenerationalControlThread::GCMode mode = _control_thread->gc_mode();
 64     if (mode == ShenandoahGenerationalControlThread::none) {
 65       if (should_start_metaspace_gc()) {
 66         if (request_concurrent_gc(GLOBAL)) {
 67           log_info(gc)("Heuristics request for global (unload classes) accepted.");
 68         }
 69       } else {
 70         if (_young_heuristics->should_start_gc()) {
 71           // Give the old generation a chance to run. The old generation cycle
 72           // begins with a 'bootstrap' cycle that will also collect young.
 73           if (start_old_cycle()) {
 74             log_info(gc)("Heuristics request for old collection accepted");
 75           } else if (request_concurrent_gc(YOUNG)) {
 76             log_info(gc)("Heuristics request for young collection accepted");
 77           }
 78         }
 79       }
 80     } else if (mode == ShenandoahGenerationalControlThread::servicing_old) {
 81       if (start_young_cycle()) {
 82         log_info(gc)("Heuristics request to interrupt old for young collection accepted");
 83       }
 84     }
 85 
 86     regulator_sleep();
 87   }
 88 }
 89 
 90 
 91 void ShenandoahRegulatorThread::regulate_young_and_global_cycles() {
 92   while (!should_terminate()) {
 93     if (_control_thread->gc_mode() == ShenandoahGenerationalControlThread::none) {
 94       if (start_global_cycle()) {
 95         log_info(gc)("Heuristics request for global collection accepted.");
 96       } else if (start_young_cycle()) {
 97         log_info(gc)("Heuristics request for young collection accepted.");
 98       }
 99     }
100 
101     regulator_sleep();
102   }
103 }
104 
105 void ShenandoahRegulatorThread::regulator_sleep() {
106   // Wait before performing the next action. If allocation happened during this wait,
107   // we exit sooner, to let heuristics re-evaluate new conditions. If we are at idle,
108   // back off exponentially.
109   double current = os::elapsedTime();
110 
111   if (ShenandoahHeap::heap()->has_changed()) {
112     _sleep = ShenandoahControlIntervalMin;
113   } else if ((current - _last_sleep_adjust_time) * 1000 > ShenandoahControlIntervalAdjustPeriod){
114     _sleep = MIN2<uint>(ShenandoahControlIntervalMax, MAX2(1u, _sleep * 2));
115     _last_sleep_adjust_time = current;
116   }
117 
118   os::naked_short_sleep(_sleep);
119   if (LogTarget(Debug, gc, thread)::is_enabled()) {
120     double elapsed = os::elapsedTime() - current;
121     double hiccup = elapsed - double(_sleep);
122     if (hiccup > 0.001) {
123       log_debug(gc, thread)("Regulator hiccup time: %.3fs", hiccup);
124     }
125   }
126 }
127 
128 bool ShenandoahRegulatorThread::start_old_cycle() {
129   return _old_heuristics->should_start_gc() && request_concurrent_gc(OLD);
130 }
131 
132 bool ShenandoahRegulatorThread::start_young_cycle() {
133   return _young_heuristics->should_start_gc() && request_concurrent_gc(YOUNG);
134 }
135 
136 bool ShenandoahRegulatorThread::start_global_cycle() {
137   return _global_heuristics->should_start_gc() && request_concurrent_gc(GLOBAL);
138 }
139 
140 bool ShenandoahRegulatorThread::request_concurrent_gc(ShenandoahGenerationType generation) {
141   double now = os::elapsedTime();
142   bool accepted = _control_thread->request_concurrent_gc(generation);
143   if (LogTarget(Debug, gc, thread)::is_enabled() && accepted) {
144     double wait_time = os::elapsedTime() - now;
145     if (wait_time > 0.001) {
146       log_debug(gc, thread)("Regulator waited %.3fs for control thread to acknowledge request.", wait_time);
147     }
148   }
149   return accepted;
150 }
151 
152 void ShenandoahRegulatorThread::stop_service() {
153   log_info(gc)("%s: Stop requested.", name());
154 }
155 
156 bool ShenandoahRegulatorThread::should_start_metaspace_gc() {
157   // The generational mode can, at present, only unload classes during a global
158   // cycle. For this reason, we treat an oom in metaspace as a _trigger_ for a
159   // global cycle. But, we check other prerequisites before starting a gc that won't
160   // unload anything.
161   return ClassUnloadingWithConcurrentMark
162       && _global_heuristics->can_unload_classes()
163       && _global_heuristics->has_metaspace_oom();
164 }
165