8355372: GenShen: Test gc/shenandoah/generational/TestOldGrowthTriggers.java fails with UseCompactObjectHeaders enabled #24888

earthling-amzn · 2025-04-25T20:40:09Z

Add a test case for -XX:+UseCompactObjectHeaders, increase pressure on old generation. I ran the test (which includes a compact object headers case now) fifty times without failure.

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JDK-8355372: GenShen: Test gc/shenandoah/generational/TestOldGrowthTriggers.java fails with UseCompactObjectHeaders enabled (Bug - P4)

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Y. Srinivas Ramakrishna (@ysramakrishna - Reviewer)
Kelvin Nilsen (@kdnilsen - Committer) Review applies to 9c991cfa

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…neration

bridgekeeper · 2025-04-25T20:40:59Z

👋 Welcome back wkemper! 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 · 2025-04-25T20:41:47Z

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

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

8355372: GenShen: Test gc/shenandoah/generational/TestOldGrowthTriggers.java fails with UseCompactObjectHeaders enabled

Reviewed-by: ysr, kdnilsen

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bf52eb0: 8355632: WhiteBox.waitForReferenceProcessing() fails assert for return type
c2485d5: 8351113: RC2ParameterSpec throws IllegalArgumentException when offset is negative
ead6757: 8342283: CDS cannot handle a large number of classes
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openjdk · 2025-04-25T20:42:22Z

@earthling-amzn The following labels will be automatically applied to this pull request:

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mlbridge · 2025-04-25T20:45:21Z

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01: Full - Incremental (70b36ac5)
00: Full (9c991cfa)

ysramakrishna

Looks fine but left some thoughts, although you probably don't want to change anything if this setting is working to induce the behavior you want to test.

A whitebox test may be better in the future rather than having to tweak test settings to induce the right behavior to trigger old growth.

ysramakrishna · 2025-04-25T23:41:24Z

test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java

-                    case 0:
-                        // 50% chance of creating garbage
-                        array[replaceIndex] = array[replaceIndex].max(array[deriveIndex]);
-                        break;
-                    case 1:
-                        // 50% chance of creating garbage
-                        array[replaceIndex] = array[replaceIndex].min(array[deriveIndex]);
-                        break;


Could you have left this in place & reduced the heap size of the UseCompactHeaders test to half the current setting to induce the trigger?

ysramakrishna · 2025-04-25T23:42:46Z

test/hotspot/jtreg/gc/shenandoah/generational/TestOldGrowthTriggers.java

            for (int i = 0; i < ArraySize; i++) {
                int replaceIndex = r.nextInt(ArraySize);
                int deriveIndex = r.nextInt(ArraySize);
                switch (i & 0x3) {


...otherwise could you just do (i & 0x1) here and change cases 2 & 3 to cases 0 & 1?

MBaesken · 2025-04-28T07:04:28Z

Hi @earthling-amzn I added your PR to our build/test queue, let's see if the issues we observed go away on all platforms!

kdnilsen

Changes look good to me.

earthling-amzn · 2025-04-28T21:18:31Z

@MBaesken - thank you! Please let us know how it goes.

@ysramakrishna - I wanted to increase pressure specifically on the old generation. I'm not sure reducing the heap size alone would do that. As you point out, the cases in the switch statement do look a bit silly now. I'll make the change you suggested.

MBaesken · 2025-04-29T07:39:20Z

thank you! Please let us know how it goes.

Unfortunately, not so good .
On darwin x86_64 fastdebug,

gc/shenandoah/generational/TestOldGrowthTriggers.java

triggers now this crash/assert


#  Internal Error (/priv/jenkins/client-home/workspace/openjdk-jdk-dev-macos_x86_64-dbg/jdk/src/hotspot/share/gc/shenandoah/shenandoahGenerationalControlThread.cpp:607), pid=58469, tid=18179
#  assert(_degen_point == ShenandoahGC::_degenerated_unset) failed: Should not be set yet: Outside of Cycle

Stack: [0x000070000fc5b000,0x000070000fd5b000],  sp=0x000070000fd5aae0,  free space=1022k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V  [libjvm.dylib+0x1576749]  VMError::report(outputStream*, bool)+0x1ef9  (shenandoahGenerationalControlThread.cpp:607)
V  [libjvm.dylib+0x157a65b]  VMError::report_and_die(int, char const*, char const*, __va_list_tag*, Thread*, unsigned char*, void const*, void const*, char const*, int, unsigned long)+0x60b
V  [libjvm.dylib+0x72bd08]  report_vm_error(char const*, int, char const*, char const*, ...)+0xd8
V  [libjvm.dylib+0x121e75a]  ShenandoahGenerationalControlThread::check_cancellation_or_degen(ShenandoahGC::ShenandoahDegenPoint)+0x14a
V  [libjvm.dylib+0x121e455]  ShenandoahGenerationalControlThread::service_concurrent_cycle(ShenandoahGeneration*, GCCause::Cause, bool)+0x165
V  [libjvm.dylib+0x121cd72]  ShenandoahGenerationalControlThread::run_gc_cycle(ShenandoahGenerationalControlThread::ShenandoahGCRequest const&)+0x1a2
V  [libjvm.dylib+0x121c8b2]  ShenandoahGenerationalControlThread::run_service()+0x142
V  [libjvm.dylib+0x6a798b]  ConcurrentGCThread::run()+0x1b
V  [libjvm.dylib+0x14bfa5c]  Thread::call_run()+0xbc
V  [libjvm.dylib+0x1060ff7]  thread_native_entry(Thread*)+0x137
C  [libsystem_pthread.dylib+0x618b]  _pthread_start+0x63
C  [libsystem_pthread.dylib+0x1ae3]  thread_start+0xf

MBaesken · 2025-04-29T14:26:43Z

Unfortunately, not so good .
On darwin x86_64 fastdebug,

gc/shenandoah/generational/TestOldGrowthTriggers.java

triggers now this crash/assert

Seems we have for this already
https://bugs.openjdk.org/browse/JDK-8355789
JDK-8355789: GenShen: assert(_degen_point == ShenandoahGC::_degenerated_unset) failed: Should not be set yet: Outside of Cycle

earthling-amzn · 2025-04-29T17:32:56Z

@MBaesken - we have a PR for that assert under review: #24940

ysramakrishna

ok

earthling-amzn · 2025-04-30T15:36:32Z

@MBaesken , have you had a chance to retest after PR#24940 was integrated?

earthling-amzn · 2025-05-01T17:39:39Z

/integrate

openjdk · 2025-05-01T17:40:57Z

Going to push as commit 9e26b9f.
Since your change was applied there have been 123 commits pushed to the master branch:

394961c: 8328914: Document the java.security.debug property in javadoc
cf0db96: 8354084: Streamline XPath API's extension function control
6b553ac: 8277424: javax/net/ssl/TLSCommon/TLSTest.java fails with connection refused
... and 120 more: https://git.openjdk.org/jdk/compare/74a2c831a2af55c66317ca8aead53fde2a2a6900...master

Your commit was automatically rebased without conflicts.

openjdk · 2025-05-01T17:41:06Z

@earthling-amzn Pushed as commit 9e26b9f.

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

MBaesken · 2025-05-02T06:37:04Z

have you had a chance to retest after PR#24940 was integrated?

Did not see the issue again after this (of course this is no 'proof' that they will never come back), so I would say looks good !

Add test case for compact object headers, increase pressure on old ge…

9c991cf

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openjdk bot added the rfr Pull request is ready for review label Apr 25, 2025

openjdk bot added hotspot-gc hotspot-gc-dev@openjdk.org shenandoah shenandoah-dev@openjdk.org labels Apr 25, 2025

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earthling-amzn deleted the old-growth-triggers-test branch October 7, 2025 17:06

8355372: GenShen: Test gc/shenandoah/generational/TestOldGrowthTriggers.java fails with UseCompactObjectHeaders enabled #24888

8355372: GenShen: Test gc/shenandoah/generational/TestOldGrowthTriggers.java fails with UseCompactObjectHeaders enabled #24888

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