8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO #28242

rgithubli · 2025-11-11T18:24:25Z

Setting ergo flags using FLAG_SET_ERGO, instead of FLAG_SET_DEFAULT, so we can have the right origin info.

For ShenandoahEvacReserve change: when we use shenandoah passive mode and degen is also turned off (-XX:ShenandoahGCMode=passive -XX:-ShenandoahDegeneratedGC), we set the ShenandoahEvacReserve to 0:

jdk/src/hotspot/share/gc/shenandoah/mode/shenandoahPassiveMode.cpp

Lines 40 to 42 in c6a8027

    
           if (!ShenandoahDegeneratedGC) { 
        
             SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0); 
        
           }

FLAG_SET_DEFAULT doesn't check the range but FLAG_SET_ERGO does so some of the jtreg would fail because of this change. Had to move this ergo setting to regular FLAG_SET_DEFAULT.

Testing: jtreg gc. GHA pending.

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Issue

JDK-8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO (Bug - P4)

Reviewers

Y. Srinivas Ramakrishna (@ysramakrishna - Reviewer) Review applies to 1a5a09bf
Cesar Soares Lucas (@JohnTortugo - Committer) Review applies to 1a5a09bf
Xiaolong Peng (@pengxiaolong - Committer)
William Kemper (@earthling-amzn - Reviewer)

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bridgekeeper · 2025-11-11T18:26:27Z

👋 Welcome back rgithubli! 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.

openjdk · 2025-11-11T18:27:09Z

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

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

8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO

Reviewed-by: xpeng, wkemper, ysr, cslucas

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At the time when this comment was updated there had been 82 new commits pushed to the master branch:

bfc048a: 8371608: Jtreg test jdk/internal/vm/Continuation/Fuzz.java sometimes fails with (fast)debug binaries
8102f43: 8371480: VerifyError after JDK-8369654
7d78818: 8274178: G1: Occupancy value in IHOP logging and JFR event is inaccurate
... and 79 more: https://git.openjdk.org/jdk/compare/e34a831814996be3e0a2df86b11b1718a76ea558...master

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openjdk · 2025-11-11T18:27:53Z

@rgithubli The following labels will be automatically applied to this pull request:

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mlbridge · 2025-11-11T18:31:36Z

Webrevs

ysramakrishna

Reviewed the ergo flg setting macro changes. They look good to me.

For the passive mode that requires allowing evac reserve of 0, I'll request @kdnilsen or @earthling-amzn to review.

/reviewers 2

openjdk · 2025-11-11T22:23:19Z

@ysramakrishna
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

earthling-amzn · 2025-11-11T23:04:52Z

Hmm, setting ShenandoahEvacReserve to zero will cause a divide by zero error in other modes (it will even cause a divide by zero error in the passive mode if ShenandoahDegeneratedGC is enabled). I'd rather contain the accommodation for this configuration to the passive mode, than accept values that will cause crashes. Could we "inline" the macro on line 41 and allow zero only for this special configuration (passive mode and only full gcs) by changing the "inlined" macro to use SET_DEFAULT still?

earthling-amzn · 2025-11-11T23:06:25Z

src/hotspot/share/gc/shenandoah/shenandoah_globals.hpp

@@ -353,7 +353,7 @@
          "evacuation collection set (comprised of both young and old "     \
          "regions) is also bounded by this parameter.  In percents of "    \
          "total (young-generation) heap size.")                            \
-          range(1,100)                                                      \
+          range(0,100)                                                      \


If we allow this, somebody will file a bug because -XX:ShenandoahEvacReserve=0 will cause other modes to crash with divide by zero error.

OK, I'll keep the range as it is (1,100), but instead of setting the default with ergo at here:

jdk/src/hotspot/share/gc/shenandoah/mode/shenandoahPassiveMode.cpp

Lines 40 to 42 in c6a8027

if (!ShenandoahDegeneratedGC) {

SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);

}

I'll just use FLAG_SET_DEFAULT to bypass the check? We wouldn't have the data source origin in passive mode which is only meant to be diagnostic, but that's better than causing problems in the regular mode.

Ah, missed your general comment above. I think we're talking about the same solution. I'll update the passive mode to use FLAG_SET_DEFAULT.

Yeah, that's what I was suggesting. Thanks!

Can we put the lower bound back to 1 now?

Sorry, forgot. Updating.

rgithubli · 2025-11-12T23:05:01Z

GHA test test/jdk/java/util/Arrays/SortingNearlySortedPrimitive.java failed, but it uses g1, should be unrelated:

 # JRE version: OpenJDK Runtime Environment (26.0) (build 26-internal-rgithubli-6200456b7130997d227dd5a128e4cefbd05059b5)
# Java VM: OpenJDK 64-Bit Server VM (26-internal-rgithubli-6200456b7130997d227dd5a128e4cefbd05059b5, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V  [libjvm.so+0x6765ff]  frame::sender(RegisterMap*) const+0x29f

It passed on my local. Rerun on GHA and check hs_err log.

Should be a non related compiler issue. Opened a JBS: https://bugs.openjdk.org/browse/JDK-8371747

earthling-amzn

Thank you!

rgithubli · 2025-11-13T17:43:14Z

/integrate

openjdk · 2025-11-13T17:44:50Z

@rgithubli
Your change (at version 6200456) is now ready to be sponsored by a Committer.

pengxiaolong · 2025-11-13T17:59:19Z

/sponsor

openjdk · 2025-11-13T18:01:58Z

Going to push as commit 2199b5f.
Since your change was applied there have been 82 commits pushed to the master branch:

bfc048a: 8371608: Jtreg test jdk/internal/vm/Continuation/Fuzz.java sometimes fails with (fast)debug binaries
8102f43: 8371480: VerifyError after JDK-8369654
7d78818: 8274178: G1: Occupancy value in IHOP logging and JFR event is inaccurate
... and 79 more: https://git.openjdk.org/jdk/compare/e34a831814996be3e0a2df86b11b1718a76ea558...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-11-13T18:02:13Z

@pengxiaolong @rgithubli Pushed as commit 2199b5f.

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

8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO

1a5a09b

rgithubli marked this pull request as ready for review November 11, 2025 18:24

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Use FLAG_SET_DEFAULT for ShenandoahEvacReserve in passive

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rgithubli requested a review from earthling-amzn November 12, 2025 01:35

Move ShenandoahEvacReserve back to (1,100)

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	if (!ShenandoahDegeneratedGC) {
	SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);
	}

8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO #28242

8371381: [Shenandoah] Setting ergo flags should use FLAG_SET_ERGO #28242

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