RFR: 8364114: Test TestHugePageDecisionsAtVMStartup.java#LP_enabled fails when no free hugepage [v3]

[Thomas Stuefe]

On Sat, 26 Jul 2025 04:33:20 GMT, SendaoYan <syan at openjdk.org> wrote:

>> 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.
>
> SendaoYan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Make explicitAvailableHugePageNumber as a member of HugePageConfiguration

Okay

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Marked as reviewed by stuefe (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26480#pullrequestreview-3057668223