7903448: JMH: Override the use of compiler hints using a system property #96

gilles-duboscq · 2023-03-07T16:37:01Z

Using -Djmh.compilerhints.mode=true will force the use of compiler hints. -Djmh.compilerhints.mode=false will prevent the use of compiler hints. When the system property is not set, the current beahviour based on vm name and version will be used by default.

This is especially useful when working with uncommon / rare JVMs or when adding compiler hints support to a new JVM.

I considered auto-detecting support for compiler hints but that didn't fit very well in the current code and required much more intrusive changes.

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CODETOOLS-7903448: JMH: Override the use of compiler hints using a system property

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Aleksey Shipilev (@shipilev - Committer)

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bridgekeeper · 2023-03-07T16:38:19Z

👋 Welcome back gdub! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

mlbridge · 2023-03-07T16:44:13Z

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shipilev

Okay, I understand the use case. But I also think that accepting a boolean as jmh.compilerhints.mode is ambiguous, especially if we ask questions about defaults :) It would be cleaner to do it like we do it for Blackholes:

public enum CompilerHintsMode {
   FORCE_ON("Forced on"),
   FORCE_OFF("Forced off"),
   AUTO("Automatically selected"),
}

Then parse that enum off the jmh.compilerhints.mode, default to AUTO.

gilles-duboscq · 2023-03-23T11:23:11Z

Good idea. I'll do

shipilev · 2023-03-23T11:59:33Z

Also, go to https://github.com/gilles-duboscq/jmh/actions and press a large green button to enable PR testing.

Using `-Djmh.compilerhints.mode=FORCE_ON` will force the use of compiler hints. `-Djmh.compilerhints.mode=FORCE_OFF` will prevent the use of compiler hints. When the system property is not set, or when it is set to `AUTO`, the current beahviour based on vm name and version will be used.

openjdk · 2023-03-23T18:39:50Z

@gilles-duboscq Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

gilles-duboscq · 2023-03-23T18:41:24Z

I have changed the jmh.compilerhints.mode system property to accept the 3 suggested values and implemented it following the implementation of the blackhole modes.

shipilev

I have more comments, apologies :)

shipilev · 2023-03-24T08:53:39Z

jmh-core/src/main/java/org/openjdk/jmh/runner/CompilerHints.java

    /**
     * FIXME (low priority): check if supplied JVM is hint compatible. This test is applied to the Runner VM,
     * not the Forked and may therefore be wrong if the forked VM is not the same JVM
     */
-    private static boolean isHintCompatibleVM() {
+    private static boolean compilerHintsEnabled() {
+        if (compilerHintsEnabled != null) {


Where do we set compilerHintsEnabled? I think it needs to be set before every return from this method.

shipilev · 2023-03-24T08:55:16Z

jmh-core/src/main/java/org/openjdk/jmh/runner/CompilerHints.java

+        out.print("# Compiler hints: " + (compilerHintsEnabled() ? "enabled" : "disabled") + " (" + compilerHintsSelect().desc() + ")");
+        out.println();


Let's print this only if !compilerHintsSelect().isAuto(). The normal use case is having compiler hints transparently enabled. This is quite a bit different from Blackhole that does have a normal variance in settings...

jmh-core/src/main/java/org/openjdk/jmh/runner/CompilerHints.java

shipilev · 2023-04-12T11:18:37Z

Ping @gilles-duboscq -- do you want to complete this, or want me to take over?

gilles-duboscq · 2023-04-12T12:01:38Z

Other things have taken over but i was still planning to get back to this within the next 1-2 weeks. If somebody else needs that faster, feel free to take over.
Thanks for the review feedback.

shipilev · 2023-04-13T09:34:30Z

Other things have taken over but i was still planning to get back to this within the next 1-2 weeks. If somebody else needs that faster, feel free to take over. Thanks for the review feedback.

That's fine, there is no time pressure to complete this work. Looking forward to new version in a few weeks. I plan to have the next JMH release some time in May.

Only print compiler hints status when it is forced

shipilev

This version looks good!

There are some flukes in GHA testing, but they all seem to be environmental.

openjdk · 2023-04-24T08:37:25Z

@gilles-duboscq This change now passes all automated pre-integration checks.

After integration, the commit message for the final commit will be:

7903448: JMH: Override the use of compiler hints using a system property

Reviewed-by: shade

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 4 new commits pushed to the master branch:

c6178ca: 7903461: JMH: perfasm profiler misses some jump edges
8716778: 7903455: JMH: Add "mempool" profiler
e88ed82: 7903451: JMH: Refactor internal Optional usages
2f21ef2: 7903439: JMH: Print help to stdout instead of stderr

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gilles-duboscq · 2023-04-24T09:01:05Z

/integrate

openjdk · 2023-04-24T09:02:22Z

@gilles-duboscq
Your change (at version 9c1617a) is now ready to be sponsored by a Committer.

shipilev · 2023-04-24T09:17:37Z

/sponsor

openjdk · 2023-04-24T09:19:16Z

Going to push as commit c5c93a2.
Since your change was applied there have been 4 commits pushed to the master branch:

c6178ca: 7903461: JMH: perfasm profiler misses some jump edges
8716778: 7903455: JMH: Add "mempool" profiler
e88ed82: 7903451: JMH: Refactor internal Optional usages
2f21ef2: 7903439: JMH: Print help to stdout instead of stderr

Your commit was automatically rebased without conflicts.

openjdk · 2023-04-24T09:19:33Z

@shipilev @gilles-duboscq Pushed as commit c5c93a2.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

openjdk bot added the rfr Pull request is ready for review label Mar 7, 2023

shipilev changed the title ~~Allow forcing the use of compiler hints using a system property~~ 7903448: JMH: Override the use compiler hints using a system property Mar 23, 2023

shipilev changed the title ~~7903448: JMH: Override the use compiler hints using a system property~~ 7903448: JMH: Override the use of compiler hints using a system property Mar 23, 2023

shipilev reviewed Mar 23, 2023

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gilles-duboscq force-pushed the force-compiler-hints branch from 8996a68 to 5e550e4 Compare March 23, 2023 18:38

shipilev requested changes Mar 24, 2023

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Split CompilerHintsSelect.AUTO into AUTO_ON/AUTO_OFF

9c1617a

Only print compiler hints status when it is forced

shipilev approved these changes Apr 24, 2023

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openjdk bot added the sponsor Pull request is ready to be sponsored label Apr 24, 2023

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7903448: JMH: Override the use of compiler hints using a system property #96

7903448: JMH: Override the use of compiler hints using a system property #96

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		out.print("# Compiler hints: " + (compilerHintsEnabled() ? "enabled" : "disabled") + " (" + compilerHintsSelect().desc() + ")");
		out.println();

7903448: JMH: Override the use of compiler hints using a system property #96

7903448: JMH: Override the use of compiler hints using a system property #96

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