1/*
2 * Copyright 2009 Google Inc.  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
24import java.util.*;
25import java.io.*;
26
27/**
28 * A manual test that demonstrates the ability to start a subprocess
29 * on Linux without getting ENOMEM.  Run this test like:
30 *
31 * java -Xmx7000m BigFork
32 *
33 * providing a -Xmx flag suitable for your operating environment.
34 * Here's the bad old behavior:
35 *
36 * ==> java -Xmx7000m -esa -ea BigFork
37 * -------
38 * CommitLimit:   6214700 kB
39 * Committed_AS:  2484452 kB
40 * -------
41 * size=4.6GB
42 * -------
43 * CommitLimit:   6214700 kB
44 * Committed_AS:  7219680 kB
45 * -------
46 * Exception in thread "main" java.io.IOException: Cannot run program "/bin/true": java.io.IOException: error=12, Cannot allocate memory
47 *         at java.lang.ProcessBuilder.start(ProcessBuilder.java:1018)
48 *         at BigFork.main(BigFork.java:79)
49 * Caused by: java.io.IOException: java.io.IOException: error=12, Cannot allocate memory
50 *         at java.lang.UNIXProcess.<init>(UNIXProcess.java:190)
51 *         at java.lang.ProcessImpl.start(ProcessImpl.java:128)
52 *         at java.lang.ProcessBuilder.start(ProcessBuilder.java:1010)
53 *         ... 1 more
54 */
55public class BigFork {
56    static final Random rnd = new Random();
57    static void touchPages(byte[] chunk) {
58        final int pageSize = 4096;
59        for (int i = 0; i < chunk.length; i+= pageSize) {
60            chunk[i] = (byte) rnd.nextInt();
61        }
62    }
63
64    static void showCommittedMemory() throws IOException {
65        BufferedReader r =
66            new BufferedReader(
67                new InputStreamReader(
68                    new FileInputStream("/proc/meminfo")));
69        System.out.println("-------");
70        String line;
71        while ((line = r.readLine()) != null) {
72            if (line.startsWith("Commit")) {
73                System.out.printf("%s%n", line);
74            }
75        }
76        System.out.println("-------");
77    }
78
79    public static void main(String[] args) throws Throwable {
80        showCommittedMemory();
81
82        final int chunkSize = 1024 * 1024 * 100;
83        List<byte[]> chunks = new ArrayList<byte[]>(100);
84        try {
85            for (;;) {
86                byte[] chunk = new byte[chunkSize];
87                touchPages(chunk);
88                chunks.add(chunk);
89            }
90        } catch (OutOfMemoryError e) {
91            chunks.set(0, null);        // Free up one chunk
92            System.gc();
93            int size = chunks.size();
94            System.out.printf("size=%.2gGB%n", (double)size/10);
95
96            showCommittedMemory();
97
98            // Can we fork/exec in our current bloated state?
99            Process p = new ProcessBuilder("/bin/true").start();
100            p.waitFor();
101        }
102    }
103}
104