1 /*
2 * Copyright (c) 2015, 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 #include "precompiled.hpp"
25 #include "gc/z/zGlobals.hpp"
26 #include "gc/z/zTask.hpp"
27 #include "gc/z/zThread.hpp"
28 #include "gc/z/zWorkers.inline.hpp"
29 #include "runtime/os.hpp"
30 #include "runtime/mutexLocker.inline.hpp"
31 #include "runtime/safepoint.hpp"
32
33 static uint calculate_nworkers_based_on_ncpus(double cpu_share_in_percent) {
34 return ceil(os::initial_active_processor_count() * cpu_share_in_percent / 100.0);
35 }
36
37 static uint calculate_nworkers_based_on_heap_size(double reserve_share_in_percent) {
38 const int nworkers = ((MaxHeapSize * (reserve_share_in_percent / 100.0)) - ZPageSizeMedium) / ZPageSizeSmall;
39 return MAX2(nworkers, 1);
40 }
41
42 static uint calculate_nworkers(double cpu_share_in_percent) {
43 // Cap number of workers so that we never use more than 10% of the max heap
44 // for the reserve. This is useful when using small heaps on large machines.
45 return MIN2(calculate_nworkers_based_on_ncpus(cpu_share_in_percent),
46 calculate_nworkers_based_on_heap_size(10.0));
47 }
48
49 uint ZWorkers::calculate_nparallel() {
50 // Use 60% of the CPUs, rounded up. We would like to use as many threads as
51 // possible to increase parallelism. However, using a thread count that is
52 // close to the number of processors tends to lead to over-provisioning and
53 // scheduling latency issues. Using 60% of the active processors appears to
54 // be a fairly good balance.
55 return calculate_nworkers(60.0);
56 }
57
58 uint ZWorkers::calculate_nconcurrent() {
59 // Use 12.5% of the CPUs, rounded up. The number of concurrent threads we
60 // would like to use heavily depends on the type of workload we are running.
61 // Using too many threads will have a negative impact on the application
62 // throughput, while using too few threads will prolong the GC-cycle and
63 // we then risk being out-run by the application. Using 12.5% of the active
64 // processors appears to be a fairly good balance.
65 return calculate_nworkers(12.5);
66 }
67
68 class ZWorkersInitializeTask : public ZTask {
69 private:
70 const uint _nworkers;
71 uint _started;
72 Monitor _monitor;
73
74 public:
75 ZWorkersInitializeTask(uint nworkers) :
76 ZTask("ZWorkersInitializeTask"),
77 _nworkers(nworkers),
78 _started(0),
79 _monitor(Monitor::leaf,
80 "ZWorkersInitialize",
81 false /* allow_vm_block */,
82 Monitor::_safepoint_check_never) {}
83
84 virtual void work() {
85 // Register as worker
86 ZThread::set_worker();
87
88 // Wait for all threads to start
89 MonitorLocker ml(&_monitor, Monitor::_no_safepoint_check_flag);
90 if (++_started == _nworkers) {
91 // All threads started
92 ml.notify_all();
93 } else {
94 while (_started != _nworkers) {
95 ml.wait();
96 }
97 }
98 }
99 };
100
101 ZWorkers::ZWorkers() :
102 _boost(false),
103 _workers("ZWorker",
104 nworkers(),
105 true /* are_GC_task_threads */,
106 true /* are_ConcurrentGC_threads */) {
107
108 log_info(gc, init)("Workers: %u parallel, %u concurrent", nparallel(), nconcurrent());
109
110 // Initialize worker threads
111 _workers.initialize_workers();
112 _workers.update_active_workers(nworkers());
113 if (_workers.active_workers() != nworkers()) {
114 vm_exit_during_initialization("Failed to create ZWorkers");
115 }
116
117 // Execute task to register threads as workers. This also helps
118 // reduce latency in early GC pauses, which otherwise would have
119 // to take on any warmup costs.
120 ZWorkersInitializeTask task(nworkers());
121 run(&task, nworkers());
122 }
123
124 void ZWorkers::set_boost(bool boost) {
125 if (boost) {
126 log_debug(gc)("Boosting workers");
127 }
128
129 _boost = boost;
130 }
131
132 void ZWorkers::run(ZTask* task, uint nworkers) {
133 log_debug(gc, task)("Executing Task: %s, Active Workers: %u", task->name(), nworkers);
134 _workers.update_active_workers(nworkers);
135 _workers.run_task(task->gang_task());
136 }
137
138 void ZWorkers::run_parallel(ZTask* task) {
139 assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
140 run(task, nparallel());
141 }
142
143 void ZWorkers::run_concurrent(ZTask* task) {
144 run(task, nconcurrent());
145 }
146
147 void ZWorkers::threads_do(ThreadClosure* tc) const {
148 _workers.threads_do(tc);
149 }
150
151 void ZWorkers::print_threads_on(outputStream* st) const {
152 _workers.print_worker_threads_on(st);
153 }