1 /*
  2  * Copyright (c) 2013, 2021, Red Hat, Inc. 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 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLTHREAD_HPP
 26 #define SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLTHREAD_HPP
 27 
 28 #include "gc/shared/gcCause.hpp"
 29 #include "gc/shared/concurrentGCThread.hpp"
 30 #include "gc/shenandoah/shenandoahGC.hpp"
 31 #include "gc/shenandoah/shenandoahHeap.hpp"
 32 #include "gc/shenandoah/shenandoahPadding.hpp"
 33 #include "gc/shenandoah/shenandoahSharedVariables.hpp"
 34 #include "runtime/task.hpp"
 35 #include "utilities/ostream.hpp"
 36 
 37 // Periodic task is useful for doing asynchronous things that do not require (heap) locks,
 38 // or synchronization with other parts of collector. These could run even when ShenandoahConcurrentThread
 39 // is busy driving the GC cycle.
 40 class ShenandoahPeriodicTask : public PeriodicTask {
 41 private:
 42   ShenandoahControlThread* _thread;
 43 public:
 44   ShenandoahPeriodicTask(ShenandoahControlThread* thread) :
 45           PeriodicTask(100), _thread(thread) {}
 46   virtual void task();
 47 };
 48 
 49 // Periodic task to notify blocked paced waiters.
 50 class ShenandoahPeriodicPacerNotify : public PeriodicTask {
 51 public:
 52   ShenandoahPeriodicPacerNotify() : PeriodicTask(PeriodicTask::min_interval) {}
 53   virtual void task();
 54 };
 55 
 56 class ShenandoahControlThread: public ConcurrentGCThread {
 57   friend class VMStructs;
 58 
 59 private:
 60   // While we could have a single lock for these, it may risk unblocking
 61   // GC waiters when alloc failure GC cycle finishes. We want instead
 62   // to make complete explicit cycle for for demanding customers.
 63   Monitor _alloc_failure_waiters_lock;
 64   Monitor _gc_waiters_lock;
 65   Monitor _control_lock;
 66   ShenandoahPeriodicTask _periodic_task;
 67   ShenandoahPeriodicPacerNotify _periodic_pacer_notify_task;
 68 
 69 public:
 70   typedef enum {
 71     none,
 72     concurrent_normal,
 73     stw_degenerated,
 74     stw_full,
 75     marking_old
 76   } GCMode;
 77 
 78   void run_service();
 79   void stop_service();
 80 
 81   size_t get_gc_id();
 82 
 83 private:
 84   ShenandoahSharedFlag _allow_old_preemption;
 85   ShenandoahSharedFlag _preemption_requested;
 86   ShenandoahSharedFlag _gc_requested;
 87   ShenandoahSharedFlag _alloc_failure_gc;
 88   ShenandoahSharedFlag _graceful_shutdown;
 89   ShenandoahSharedFlag _do_counters_update;
 90   ShenandoahSharedFlag _force_counters_update;
 91   GCCause::Cause       _requested_gc_cause;
 92   GenerationMode       _requested_generation;
 93   ShenandoahGC::ShenandoahDegenPoint _degen_point;
 94   ShenandoahGeneration* _degen_generation;
 95 
 96   shenandoah_padding(0);
 97   volatile size_t _allocs_seen;
 98   shenandoah_padding(1);
 99   volatile size_t _gc_id;
100   shenandoah_padding(2);
101   volatile GCMode _mode;
102   shenandoah_padding(3);
103 
104   bool check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point);
105   void resume_concurrent_old_cycle(ShenandoahGeneration* generation, GCCause::Cause cause);
106   void service_concurrent_cycle(ShenandoahGeneration* generation, GCCause::Cause cause, bool reset_old_bitmap_specially);
107   void service_stw_full_cycle(GCCause::Cause cause);
108 
109   // Return true if degenerated cycle finishes normally.  Return false if the degenerated cycle transformed itself
110   // into a full GC.
111   bool service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point);
112   void service_uncommit(double shrink_before, size_t shrink_until);
113 
114   bool try_set_alloc_failure_gc();
115   void notify_alloc_failure_waiters();
116   bool is_alloc_failure_gc();
117 
118   void reset_gc_id();
119   void update_gc_id();
120 
121   void notify_gc_waiters();
122 
123   // Handle GC request.
124   // Blocks until GC is over.
125   void handle_requested_gc(GCCause::Cause cause);
126 
127   bool is_explicit_gc(GCCause::Cause cause) const;
128   bool is_implicit_gc(GCCause::Cause cause) const;
129 
130   bool preempt_old_marking(GenerationMode generation);
131 
132   bool check_soft_max_changed() const;
133 
134 public:
135   // Constructor
136   ShenandoahControlThread();
137   ~ShenandoahControlThread();
138 
139   // Handle allocation failure from normal allocation.
140   // Blocks until memory is available.
141   void handle_alloc_failure(ShenandoahAllocRequest& req);
142 
143   // Handle allocation failure from evacuation path.
144   // Optionally blocks while collector is handling the failure.
145   void handle_alloc_failure_evac(size_t words);
146 
147   void request_gc(GCCause::Cause cause);
148   bool request_concurrent_gc(GenerationMode generation);
149 
150   void handle_counters_update();
151   void handle_force_counters_update();
152   void set_forced_counters_update(bool value);
153 
154   void notify_heap_changed();
155 
156   void pacing_notify_alloc(size_t words);
157 
158   void start();
159   void prepare_for_graceful_shutdown();
160   bool in_graceful_shutdown();
161 
162   const char* name() const { return "ShenandoahControlThread";}
163 
164   // Printing
165   void print_on(outputStream* st) const;
166   void print() const;
167 
168   void service_concurrent_normal_cycle(const ShenandoahHeap* heap,
169                                        const GenerationMode generation,
170                                        GCCause::Cause cause);
171 
172   void service_concurrent_old_cycle(const ShenandoahHeap* heap,
173                                     GCCause::Cause &cause);
174 
175   void set_gc_mode(GCMode new_mode);
176   GCMode gc_mode() {
177     return _mode;
178   }
179 
180  private:
181   static const char* gc_mode_name(GCMode mode);
182   void notify_control_thread();
183 };
184 
185 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLTHREAD_HPP