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
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMMUTRACKER_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHMMUTRACKER_HPP
27
28 #include "runtime/mutex.hpp"
29 #include "utilities/numberSeq.hpp"
30
31 class ShenandoahGeneration;
32 class ShenandoahMmuTask;
33
34 /**
35 * This class is responsible for tracking and adjusting the minimum mutator
36 * utilization (MMU). MMU is defined as the percentage of CPU time available
37 * to mutator threads over an arbitrary, fixed interval of time. This interval
38 * defaults to 5 seconds and is configured by GCPauseIntervalMillis. The class
39 * maintains a decaying average of the last 10 values. The MMU is measured
40 * by summing all of the time given to the GC threads and comparing this to
41 * the total CPU time for the process. There are OS APIs to support this on
42 * all major platforms.
43 *
44 * The time spent by GC threads is attributed to the young or old generation.
45 * The time given to the controller and regulator threads is attributed to the
46 * global generation. At the end of every collection, the average MMU is inspected.
47 * If it is below `GCTimeRatio`, this class will attempt to increase the capacity
48 * of the generation that is consuming the most CPU time. The assumption being
49 * that increasing memory will reduce the collection frequency and raise the
50 * MMU.
51 */
52 class ShenandoahMmuTracker {
53 private:
54 // These variables hold recent snapshots of cumulative quantities that are used for calculating
55 // CPU time consumed by GC and mutator threads during each GC cycle.
56 double _most_recent_timestamp;
57 double _most_recent_gc_time;
58 double _most_recent_gcu;
59 double _most_recent_mutator_time;
60 double _most_recent_mu;
61
62 // These variables hold recent snapshots of cumulative quantities that are used for reporting
63 // periodic consumption of CPU time by GC and mutator threads.
64 double _most_recent_periodic_time_stamp;
65 double _most_recent_periodic_gc_time;
66 double _most_recent_periodic_mutator_time;
67
68 size_t _most_recent_gcid;
69 uint _active_processors;
70
71 bool _most_recent_is_full;
72
73 ShenandoahMmuTask* _mmu_periodic_task;
74 TruncatedSeq _mmu_average;
75
76 void update_utilization(size_t gcid, const char* msg);
77 static void fetch_cpu_times(double &gc_time, double &mutator_time);
78
79 public:
80 explicit ShenandoahMmuTracker();
81 ~ShenandoahMmuTracker();
82
83 // This enrolls the periodic task after everything is initialized.
84 void initialize();
85
86 // At completion of each GC cycle (not including interrupted cycles), we invoke one of the following to record the
87 // GC utilization during this cycle. Incremental efforts spent in an interrupted GC cycle will be accumulated into
88 // the CPU time reports for the subsequent completed [degenerated or full] GC cycle.
89 //
90 // We may redundantly record degen and full in the case that a degen upgrades to full. When this happens, we will invoke
91 // both record_full() and record_degenerated() with the same value of gcid. record_full() is called first and the log
92 // reports such a cycle as a FULL cycle.
93 void record_young(size_t gcid);
94 void record_global(size_t gcid);
95 void record_bootstrap(size_t gcid);
96 void record_old_marking_increment(bool old_marking_done);
97 void record_mixed(size_t gcid);
98 void record_full(size_t gcid);
99 void record_degenerated(size_t gcid, bool is_old_boostrap);
100
101 // This is called by the periodic task timer. The interval is defined by
102 // GCPauseIntervalMillis and defaults to 5 seconds. This method computes
103 // the MMU over the elapsed interval and records it in a running average.
104 void report();
105 };
106
107 #endif //SHARE_GC_SHENANDOAH_SHENANDOAHMMUTRACKER_HPP