1 /*
2 * Copyright (c) 2025, 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 * @test
26 * @summary Test ForkJoinPool signalling with a virtual thread workload that oscillates
27 * between busy and idle
28 * @requires vm.continuations
29 * @requires test.thread.factory == null
30 * @run main/othervm ${test.main.class}
31 */
32
33 import java.lang.management.ManagementFactory;
34 import java.util.concurrent.Callable;
35 import java.util.concurrent.Executors;
36 import java.util.function.IntPredicate;
37 import java.util.stream.IntStream;
38 import jdk.management.VirtualThreadSchedulerMXBean;
39
40 public class UpDownLoad {
41
42 private enum Mode { SLEEP, SPIN };
43 private static volatile boolean done;
44 private static volatile Mode mode = Mode.SLEEP;
45
46 public static void main(String[] args) throws Exception {
47 int parallelism = Runtime.getRuntime().availableProcessors();
48 if (parallelism < 2) {
49 return;
50 }
51
52 Callable<?> task = () -> {
53 while (!done) {
54 switch (mode) {
55 case SPIN -> Thread.onSpinWait();
56 case SLEEP -> Thread.sleep(10);
57 }
58 }
59 return null;
60 };
61
62 try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
63 try {
64 IntStream.range(0, parallelism).forEach(_ -> executor.submit(task));
65
66 // oscillate between sleeping and spinning
67 for (int i = 1; i <= 10; i++) {
68 System.out.println("--- iteration " + i + " ---");
69
70 mode = Mode.SLEEP;
71 System.out.println("await mounted < " + parallelism);
72 awaitMounted(n -> n < parallelism);
73
74 mode = Mode.SPIN;
75 System.out.println("await mounted >= " + parallelism);
76 awaitMounted(n -> n >= parallelism);
77 }
78 } finally {
79 done = true;
80 }
81 }
82 }
83
84 static void awaitMounted(IntPredicate predicate) throws InterruptedException {
85 var bean = ManagementFactory.getPlatformMXBean(VirtualThreadSchedulerMXBean.class);
86 int attempts = 0;
87 for (;;) {
88 if (predicate.test(bean.getMountedVirtualThreadCount()))
89 return;
90 System.out.println(bean);
91 if (++attempts > 20)
92 throw new RuntimeException("Gave up");
93 Thread.sleep(500);
94 }
95 }
96 }