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 demanding customers.
 63   Monitor _alloc_failure_waiters_lock;
 64   Monitor _gc_waiters_lock;
 65   Monitor _control_lock;
 66   Monitor _regulator_lock;
 67   ShenandoahPeriodicTask _periodic_task;
 68   ShenandoahPeriodicPacerNotify _periodic_pacer_notify_task;
 69 
 70 public:
 71   typedef enum {
 72     none,
 73     concurrent_normal,
 74     stw_degenerated,
 75     stw_full,
 76     servicing_old
 77   } GCMode;
 78 
 79   void run_service();
 80   void stop_service();
 81 
 82   size_t get_gc_id();
 83 
 84 private:
 85   ShenandoahSharedFlag _allow_old_preemption;
 86   ShenandoahSharedFlag _preemption_requested;
 87   ShenandoahSharedFlag _gc_requested;
 88   ShenandoahSharedFlag _alloc_failure_gc;
 89   ShenandoahSharedFlag _graceful_shutdown;
 90   ShenandoahSharedFlag _do_counters_update;
 91   ShenandoahSharedFlag _force_counters_update;
 92   GCCause::Cause       _requested_gc_cause;
 93   GenerationMode       _requested_generation;
 94   ShenandoahGC::ShenandoahDegenPoint _degen_point;
 95   ShenandoahGeneration* _degen_generation;
 96 
 97   shenandoah_padding(0);
 98   volatile size_t _allocs_seen;
 99   shenandoah_padding(1);
100   volatile size_t _gc_id;
101   shenandoah_padding(2);
102   volatile GCMode _mode;
103   shenandoah_padding(3);
104 
105   // Returns true if the cycle has been cancelled or degenerated.
106   bool check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint point);
107 
108   // Returns true if the old generation marking completed (i.e., final mark executed for old generation).
109   bool resume_concurrent_old_cycle(ShenandoahGeneration* generation, GCCause::Cause cause);
110   void service_concurrent_cycle(ShenandoahGeneration* generation, GCCause::Cause cause, bool reset_old_bitmap_specially);
111   void service_stw_full_cycle(GCCause::Cause cause);
112 
113   // Return true if degenerated cycle finishes normally.  Return false if the degenerated cycle transformed itself
114   // into a full GC.
115   bool service_stw_degenerated_cycle(GCCause::Cause cause, ShenandoahGC::ShenandoahDegenPoint point);
116   void service_uncommit(double shrink_before, size_t shrink_until);
117 
118   // Return true if setting the flag which indicates allocation failure succeeds.
119   bool try_set_alloc_failure_gc();
120   // Notify threads waiting for GC to complete.
121   void notify_alloc_failure_waiters();
122   // True if allocation failure flag has been set.
123   bool is_alloc_failure_gc();
124 
125   void reset_gc_id();
126   void update_gc_id();
127 
128   void notify_gc_waiters();
129 
130   // Handle GC request.
131   // Blocks until GC is over.
132   void handle_requested_gc(GCCause::Cause cause);
133 
134   bool is_explicit_gc(GCCause::Cause cause) const;
135   bool is_implicit_gc(GCCause::Cause cause) const;
136 
137   // Returns true if the old generation marking was interrupted to allow a young cycle.
138   bool preempt_old_marking(GenerationMode generation);
139 
140   // Returns true if the soft maximum heap has been changed using management APIs.
141   bool check_soft_max_changed() const;
142 
143   void process_phase_timings(const ShenandoahHeap* heap);
144 
145 public:
146   // Constructor
147   ShenandoahControlThread();
148   ~ShenandoahControlThread();
149 
150   // Handle allocation failure from normal allocation.
151   // Blocks until memory is available.
152   void handle_alloc_failure(ShenandoahAllocRequest& req);
153 
154   // Handle allocation failure from evacuation path.
155   // Optionally blocks while collector is handling the failure.
156   void handle_alloc_failure_evac(size_t words);
157 
158   void request_gc(GCCause::Cause cause);
159   // Return true if the request to start a concurrent GC for the given generation succeeded.
160   bool request_concurrent_gc(GenerationMode generation);
161 
162   void handle_counters_update();
163   void handle_force_counters_update();
164   void set_forced_counters_update(bool value);
165 
166   void notify_heap_changed();
167 
168   void pacing_notify_alloc(size_t words);
169 
170   void start();
171   void prepare_for_graceful_shutdown();
172   bool in_graceful_shutdown();
173 
174   const char* name() const { return "ShenandoahControlThread";}
175 
176   // Printing
177   void print_on(outputStream* st) const;
178   void print() const;
179 
180   void service_concurrent_normal_cycle(const ShenandoahHeap* heap,
181                                        const GenerationMode generation,
182                                        GCCause::Cause cause);
183 
184   void service_concurrent_old_cycle(const ShenandoahHeap* heap,
185                                     GCCause::Cause &cause);
186 
187   void set_gc_mode(GCMode new_mode);
188   GCMode gc_mode() {
189     return _mode;
190   }
191 
192  private:
193   static const char* gc_mode_name(GCMode mode);
194   void notify_control_thread();
195 
196   void service_concurrent_cycle(const ShenandoahHeap* heap, ShenandoahGeneration* generation, GCCause::Cause &cause,
197                                 bool do_old_gc_bootstrap);
198 };
199 
200 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHCONTROLTHREAD_HPP