1 /*
  2  * Copyright (c) 2018, 2019, 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_SHENANDOAHPACER_HPP
 26 #define SHARE_GC_SHENANDOAH_SHENANDOAHPACER_HPP
 27 
 28 #include "gc/shenandoah/shenandoahNumberSeq.hpp"
 29 #include "gc/shenandoah/shenandoahPadding.hpp"
 30 #include "memory/allocation.hpp"
 31 
 32 class ShenandoahHeap;
 33 
 34 #define PACING_PROGRESS_UNINIT (-1)
 35 #define PACING_PROGRESS_ZERO   ( 0)
 36 
 37 /**
 38  * ShenandoahPacer provides allocation pacing mechanism.
 39  *
 40  * Currently it implements simple tax-and-spend pacing policy: GC threads provide
 41  * credit, allocating thread spend the credit, or stall when credit is not available.
 42  */
 43 class ShenandoahPacer : public CHeapObj<mtGC> {
 44 private:
 45   ShenandoahHeap* _heap;
 46   double _last_time;
 47   TruncatedSeq* _progress_history;
 48   Monitor* _wait_monitor;
 49   ShenandoahSharedFlag _need_notify_waiters;
 50 
 51   // Set once per phase
 52   volatile intptr_t _epoch;
 53   volatile double _tax_rate;
 54 
 55   // Heavily updated, protect from accidental false sharing
 56   shenandoah_padding(0);
 57   volatile intptr_t _budget;
 58   shenandoah_padding(1);
 59 
 60   // Heavily updated, protect from accidental false sharing
 61   shenandoah_padding(2);
 62   volatile intptr_t _progress;
 63   shenandoah_padding(3);
 64 
 65 public:
 66   ShenandoahPacer(ShenandoahHeap* heap) :
 67           _heap(heap),
 68           _last_time(os::elapsedTime()),
 69           _progress_history(new TruncatedSeq(5)),
 70           _wait_monitor(new Monitor(Mutex::safepoint-1, "ShenandoahWaitMonitor_lock", true)),
 71           _epoch(0),
 72           _tax_rate(1),
 73           _budget(0),
 74           _progress(PACING_PROGRESS_UNINIT) {}
 75 
 76   void setup_for_idle();
 77   void setup_for_mark();
 78   void setup_for_evac();
 79   void setup_for_updaterefs();
 80 
 81   void setup_for_reset();
 82 
 83   inline void report_mark(size_t words);
 84   inline void report_evac(size_t words);
 85   inline void report_updaterefs(size_t words);
 86 
 87   inline void report_alloc(size_t words);
 88 
 89   bool claim_for_alloc(size_t words, bool force);
 90   void pace_for_alloc(size_t words);
 91   void unpace_for_alloc(intptr_t epoch, size_t words);
 92 
 93   void notify_waiters();
 94 
 95   intptr_t epoch();
 96 
 97   void flush_stats_to_cycle();
 98   void print_cycle_on(outputStream* out);
 99 
100 private:
101   inline void report_internal(size_t words);
102   inline void report_progress_internal(size_t words);
103 
104   inline void add_budget(size_t words);
105   void restart_with(size_t non_taxable_bytes, double tax_rate);
106 
107   size_t update_and_get_progress_history();
108 
109   void wait(size_t time_ms);
110 };
111 
112 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHPACER_HPP