1 /*
2 * Copyright (c) 2015, 2017, 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/zTask.hpp"
26 #include "gc/z/zWorkers.inline.hpp"
27 #include "runtime/os.hpp"
28 #include "runtime/mutexLocker.hpp"
29 #include "runtime/safepoint.hpp"
30
calculate_ncpus(double share_in_percent)31 uint ZWorkers::calculate_ncpus(double share_in_percent) {
32 return ceil(os::initial_active_processor_count() * share_in_percent / 100.0);
33 }
34
calculate_nparallel()35 uint ZWorkers::calculate_nparallel() {
36 // Use 60% of the CPUs, rounded up. We would like to use as many threads as
37 // possible to increase parallelism. However, using a thread count that is
38 // close to the number of processors tends to lead to over-provisioning and
39 // scheduling latency issues. Using 60% of the active processors appears to
40 // be a fairly good balance.
41 return calculate_ncpus(60.0);
42 }
43
calculate_nconcurrent()44 uint ZWorkers::calculate_nconcurrent() {
45 // Use 12.5% of the CPUs, rounded up. The number of concurrent threads we
46 // would like to use heavily depends on the type of workload we are running.
47 // Using too many threads will have a negative impact on the application
48 // throughput, while using too few threads will prolong the GC-cycle and
49 // we then risk being out-run by the application. Using 12.5% of the active
50 // processors appears to be a fairly good balance.
51 return calculate_ncpus(12.5);
52 }
53
54 class ZWorkersWarmupTask : public ZTask {
55 private:
56 const uint _nworkers;
57 uint _started;
58 Monitor _monitor;
59
60 public:
ZWorkersWarmupTask(uint nworkers)61 ZWorkersWarmupTask(uint nworkers) :
62 ZTask("ZWorkersWarmupTask"),
63 _nworkers(nworkers),
64 _started(0),
65 _monitor(Monitor::leaf, "ZWorkersWarmup", false, Monitor::_safepoint_check_never) {}
66
work()67 virtual void work() {
68 // Wait for all threads to start
69 MonitorLockerEx ml(&_monitor, Monitor::_no_safepoint_check_flag);
70 if (++_started == _nworkers) {
71 // All threads started
72 ml.notify_all();
73 } else {
74 while (_started != _nworkers) {
75 ml.wait(Monitor::_no_safepoint_check_flag);
76 }
77 }
78 }
79 };
80
ZWorkers()81 ZWorkers::ZWorkers() :
82 _boost(false),
83 _workers("ZWorker",
84 nworkers(),
85 true /* are_GC_task_threads */,
86 true /* are_ConcurrentGC_threads */) {
87
88 log_info(gc, init)("Workers: %u parallel, %u concurrent", nparallel(), nconcurrent());
89
90 // Initialize worker threads
91 _workers.initialize_workers();
92 _workers.update_active_workers(nworkers());
93 if (_workers.active_workers() != nworkers()) {
94 vm_exit_during_initialization("Failed to create ZWorkers");
95 }
96
97 // Warm up worker threads by having them execute a dummy task.
98 // This helps reduce latency in early GC pauses, which otherwise
99 // would have to take on any warmup costs.
100 ZWorkersWarmupTask task(nworkers());
101 run(&task, nworkers());
102 }
103
set_boost(bool boost)104 void ZWorkers::set_boost(bool boost) {
105 if (boost) {
106 log_debug(gc)("Boosting workers");
107 }
108
109 _boost = boost;
110 }
111
run(ZTask * task,uint nworkers)112 void ZWorkers::run(ZTask* task, uint nworkers) {
113 log_debug(gc, task)("Executing Task: %s, Active Workers: %u", task->name(), nworkers);
114 _workers.update_active_workers(nworkers);
115 _workers.run_task(task->gang_task());
116 }
117
run_parallel(ZTask * task)118 void ZWorkers::run_parallel(ZTask* task) {
119 assert(SafepointSynchronize::is_at_safepoint(), "Should be at a safepoint");
120 run(task, nparallel());
121 }
122
run_concurrent(ZTask * task)123 void ZWorkers::run_concurrent(ZTask* task) {
124 run(task, nconcurrent());
125 }
126
threads_do(ThreadClosure * tc) const127 void ZWorkers::threads_do(ThreadClosure* tc) const {
128 _workers.threads_do(tc);
129 }
130
print_threads_on(outputStream * st) const131 void ZWorkers::print_threads_on(outputStream* st) const {
132 _workers.print_worker_threads_on(st);
133 }
134