8364114: Test TestHugePageDecisionsAtVMStartup.java#LP_enabled fails when no free hugepage

[sendaoYan]

Hi all,

The test runtime/os/TestHugePageDecisionsAtVMStartup.java#LP_enabled will fails when there is no free hugepases.
The /proc/meminfo and /sys/kernel/mm/hugepages/hugepages-*/free_hugepages says there is no free hugepage, and the JVM output also say there is available large page.

> cat /proc/meminfo | grep -i HugePages
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
FileHugePages:         0 kB
HugePages_Total:       2
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        2
Hugepagesize:       2048 kB

> ( set -x ; cat /sys/kernel/mm/hugepages/hugepages-*/free_hugepages )
+ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages /sys/kernel/mm/hugepages/hugepages-2048kB/free_hugepages
0
0

JVM output snippet from java -XX:+UseLargePages -Xlog:pagesize -version
[0.001s][info][pagesize] Large page size (2M) failed sanity check, checking if smaller large page sizes are usable
[0.001s][warning][pagesize] UseLargePages disabled, no large pages configured and available on the system.

The JVM can not use large page when there is no available large page on system, it's not a JVM bug. So I think it's not suitable to report test failure, but report SkippedException.

Change has been verified locally, test report SkippedException on the system without free hugepage, the test passes on the system with free hugepage. Test-fix only, risk is low.

---

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Issue

• JDK-8364114: Test TestHugePageDecisionsAtVMStartup.java#LP_enabled fails when no free hugepage (Enhancement - P4)

Reviewers

• Thomas Stuefe (@tstuefe - Reviewer)
• David Holmes (@dholmes-ora - Reviewer)

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8364114: Test TestHugePageDecisionsAtVMStartup.java#LP_enabled fails when no free hugepage

Reviewed-by: stuefe, dholmes

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At the time when this comment was updated there had been 20 new commits pushed to the master branch:

• e307b5c: 8363584: Sort share/utilities includes
• 4189fcb: 8362596: RISC-V: Improve _vectorizedHashCode intrinsic
• 3263361: 8360981: Remove use of Thread.stop in test/jdk/java/net/Socket/DeadlockTest.java
• ... and 17 more: https://git.openjdk.org/jdk/compare/67e93281a4f9e76419f1d6e05099ecf2214ebbfd...master

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[tstuefe]

Thanks for fixing this.

Side note, I was long on the fence about just throwing that JVM-side startup test out. Since it seems superfluous - without the test, we would just proceed allocating the heap, not get the desired large pages, which would produce almost the same result. And it is no guarantee anyway, since we may pass the test and later fail to allocate the much larger heap.

[tstuefe]

Okay

[sendaoYan]

Thanks for the reviews and suggestions @tstuefe

Do we need the second reviewer to this PR

[dholmes-ora]

Do we need the second reviewer to this PR

Yes. If it touches src/hotspot or test/hotspot, and is not a trivial fix (per the developer guide[1]) then we require two reviews.

[1] https://openjdk.org/guide/#trivial-changes

[dholmes-ora]

I can't quite see how the first version of the change was actually reading the value from /proc/meminfo, but I don't like that we parse /proc/meminfo twice now - that's unnecessarily inefficient IMO. That said, it isn't a lot of information so I won't insist on a change.

Approved.

[sendaoYan]

Thanks @tstuefe @dholmes-ora for the reviews and suggetions.

/integrate

[openjdk]

Going to push as commit 3b0da29.
Since your change was applied there have been 20 commits pushed to the master branch:

• e307b5c: 8363584: Sort share/utilities includes
• 4189fcb: 8362596: RISC-V: Improve _vectorizedHashCode intrinsic
• 3263361: 8360981: Remove use of Thread.stop in test/jdk/java/net/Socket/DeadlockTest.java
• ... and 17 more: https://git.openjdk.org/jdk/compare/67e93281a4f9e76419f1d6e05099ecf2214ebbfd...master

Your commit was automatically rebased without conflicts.

[openjdk]

@sendaoYan Pushed as commit 3b0da29.

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