1 /*
2 * Copyright Amazon.com Inc. 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 id=compact-headers
26 * @summary With compact object headers the max TLAB size must be strictly below a
27 * region, so a region-sized object can never be served from a TLAB (which
28 * would bypass the humongous path). The cap is only observable indirectly:
29 * a region-sized -XX:TLABSize is rejected at startup under compact headers,
30 * but accepted without them (where the max TLAB equals the region size).
31 * @bug 8387285
32 * @requires vm.gc.Shenandoah
33 * @library /test/lib
34 * @modules java.base/jdk.internal.misc
35 * java.management
36 * @run driver TestCompactHeaderTLABSize
37 */
38
39 import jdk.test.lib.process.ProcessTools;
40 import jdk.test.lib.process.OutputAnalyzer;
41
42 public class TestCompactHeaderTLABSize {
43
44 // Minimum Shenandoah region size; the only size at which the un-capped max TLAB
45 // would otherwise equal the region size.
46 static final String REGION_SIZE = "256K";
47
48 public static void main(String[] args) throws Exception {
49 // With compact object headers, the max TLAB is capped one word below the
50 // region, so requesting a region-sized TLAB must be rejected at startup.
51 OutputAnalyzer coh = ProcessTools.executeLimitedTestJava(
52 "-XX:+UnlockExperimentalVMOptions",
53 "-XX:+UnlockDiagnosticVMOptions",
54 "-XX:+UseShenandoahGC",
55 "-XX:+UseCompactObjectHeaders",
56 "-XX:ShenandoahRegionSize=" + REGION_SIZE,
57 "-XX:TLABSize=" + REGION_SIZE,
58 "-Xmx512m",
59 "-version");
60 coh.shouldContain("must be less than or equal to ergonomic TLAB maximum size");
61 coh.shouldHaveExitValue(1);
62
63 // Without compact object headers there is no hash-code expansion, so the max
64 // TLAB equals the region size and the same region-sized TLAB is accepted.
65 OutputAnalyzer noCoh = ProcessTools.executeLimitedTestJava(
66 "-XX:+UnlockExperimentalVMOptions",
67 "-XX:+UnlockDiagnosticVMOptions",
68 "-XX:+UseShenandoahGC",
69 "-XX:-UseCompactObjectHeaders",
70 "-XX:ShenandoahRegionSize=" + REGION_SIZE,
71 "-XX:TLABSize=" + REGION_SIZE,
72 "-Xmx512m",
73 "-version");
74 noCoh.shouldHaveExitValue(0);
75
76 // Under compact headers, a TLAB one word below the region is still accepted:
77 // the cap is exactly one (object-aligned) word, not an arbitrary reduction.
78 OutputAnalyzer atCap = ProcessTools.executeLimitedTestJava(
79 "-XX:+UnlockExperimentalVMOptions",
80 "-XX:+UnlockDiagnosticVMOptions",
81 "-XX:+UseShenandoahGC",
82 "-XX:+UseCompactObjectHeaders",
83 "-XX:ShenandoahRegionSize=" + REGION_SIZE,
84 "-XX:TLABSize=" + (256 * 1024 - 8), // one HeapWord below the region
85 "-Xmx512m",
86 "-version");
87 atCap.shouldHaveExitValue(0);
88 }
89 }