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CRIU resets j.l.VirtualThread.ForkJoinPool.parallelism after restore - #17618

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Sep 12, 2023
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CRIU resets j.l.VirtualThread.ForkJoinPool.parallelism after restore#17618
tajila merged 1 commit into
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JasonFengJ9:updatefjpparallelism

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@JasonFengJ9 JasonFengJ9 commented Jun 19, 2023 •
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CRIU resets j.l.VirtualThread.ForkJoinPool.parallelism after restore

If there is no system property jdk.virtualThreadScheduler.parallelism set at VM startup, j.l.VirtualThread.ForkJoinPool.parallelism value is reset to match Runtime.getRuntime().availableProcessors() after CRIU
restore;
Added VM_VMHelpers methods getStaticFieldObject/findinstanceFieldOffset/setObjectFieldI32;
Changed hashClassTableAt to peekClassHashTable;
Minor refactoring;
Added tests.

Signed-off-by: Jason Feng fengj@ca.ibm.com

@JasonFengJ9 JasonFengJ9 added comp:vm criu Used to track CRIU snapshot related work jdk20 labels Jun 19, 2023
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JasonFengJ9 requested a review from tajila June 19, 2023 12:21
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Comment thread runtime/vm/CRIUHelpers.cpp Outdated
Comment thread runtime/vm/CRIUHelpers.cpp Outdated
Comment thread runtime/vm/CRIUHelpers.cpp Outdated
@JasonFengJ9 JasonFengJ9 mentioned this pull request Jun 20, 2023
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JasonFengJ9 force-pushed the updatefjpparallelism branch 3 times, most recently from 4085b76 to bd167d1 Compare June 22, 2023 01:39
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JasonFengJ9 force-pushed the updatefjpparallelism branch from bd167d1 to ed5de2d Compare July 28, 2023 12:29
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JasonFengJ9 force-pushed the updatefjpparallelism branch 2 times, most recently from a29effa to a76f932 Compare July 28, 2023 14:37
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Comment thread runtime/nls/j9vm/j9vm.nls Outdated
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CRIU resets j.l.VirtualThread.ForkJoinPool.parallelism after restore
ac50591 
If there is no system property jdk.virtualThreadScheduler.parallelism
set at VM startup, j.l.VirtualThread.ForkJoinPool.parallelism value is
reset to match Runtime.getRuntime().availableProcessors() after CRIU
restore;
Added VM_VMHelpers methods
getStaticFieldObject/findinstanceFieldOffset/setObjectFieldI32;
Changed hashClassTableAt to peekClassHashTable;
Minor refactoring;
Added tests.

Signed-off-by: Jason Feng <fengj@ca.ibm.com>
@JasonFengJ9
JasonFengJ9 force-pushed the updatefjpparallelism branch from a76f932 to ac50591 Compare August 29, 2023 15:30
@tajila

tajila commented Sep 11, 2023

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Im wondering if we should just use vmconstantpool for this. Im trying to think of a downside, but I think the cost to startup is negligeable

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JasonFengJ9 commented Sep 11, 2023

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Im wondering if we should just use vmconstantpool for this. Im trying to think of a downside, but I think the cost to startup is negligeable

This mimics the earlier modification of java/util/concurrent/atomic/AtomicLong.value. There were discussions about loading it at startup via vmconstantpool #14365 (comment), it was decided not to do so to avoid unnecessary class instances.
In addition, besides minor startup costs, it also adds a dependency on OpenJDK class initialisation at OpenJ9 bootup stage though most of the time is fine.
vmconstantpool does offer a simpler way for the field modification.

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tajila commented Sep 11, 2023

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I mention it here, because with VirtualThreads ForkJoinPool will certainly be used. I guess it may not be with pre-JDK 21 builds

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tajila commented Sep 11, 2023

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jenkins compile win jdk8

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tajila commented Sep 11, 2023

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jenkins test sanity alinux64 jdk21

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tajila merged commit dce0276 into eclipse-openj9:master Sep 12, 2023
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JasonFengJ9 deleted the updatefjpparallelism branch September 12, 2023 14:32
@JasonFengJ9 JasonFengJ9 mentioned this pull request Sep 12, 2023
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