1 /*
2  * Copyright (c) 2018, 2019, Oracle and/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_SHARED_WORKERPOLICY_HPP
26 #define SHARE_GC_SHARED_WORKERPOLICY_HPP
27 
28 #include "memory/allocation.hpp"
29 #include "utilities/globalDefinitions.hpp"
30 
31 class WorkerPolicy : public AllStatic {
32   static const uint GCWorkersPerJavaThread = 2;
33 
34   static bool _debug_perturbation;
35   static uint _parallel_worker_threads;
36   static bool _parallel_worker_threads_initialized;
37 
38   static uint nof_parallel_worker_threads(uint num,
39                                           uint den,
40                                           uint switch_pt);
41 
42   // Calculates and returns the number of parallel GC threads. May
43   // be CPU-architecture-specific.
44   static uint calc_parallel_worker_threads();
45 
46 public:
47   // Returns the number of parallel threads to be used as default value of
48   // ParallelGCThreads. If that number has not been calculated, do so and
49   // save it.  Returns ParallelGCThreads if it is set on the
50   // command line.
51   static uint parallel_worker_threads();
52 
53   // Return number default GC threads to use in the next GC.
54   static uint calc_default_active_workers(uintx total_workers,
55                                           const uintx min_workers,
56                                           uintx active_workers,
57                                           uintx application_workers);
58 
59   // Return number of GC threads to use in the next GC.
60   // This is called sparingly so as not to change the
61   // number of GC workers gratuitously.
62   //   For ParNew collections
63   //   For PS scavenge and ParOld collections
64   //   For G1 evacuation pauses (subject to update)
65   //   For G1 Full GCs (subject to update)
66   // Other collection phases inherit the number of
67   // GC workers from the calls above.  For example,
68   // a CMS parallel remark uses the same number of GC
69   // workers as the most recent ParNew collection.
70   static uint calc_active_workers(uintx total_workers,
71                                   uintx active_workers,
72                                   uintx application_workers);
73 
74   // Return number of GC threads to use in the next concurrent GC phase.
75   static uint calc_active_conc_workers(uintx total_workers,
76                                        uintx active_workers,
77                                        uintx application_workers);
78 
79 };
80 
81 #endif // SHARE_GC_SHARED_WORKERPOLICY_HPP
82