RFR: 8343340: Swapping checking do not work for MetricsMemoryTester failcount [v2]

[Severin Gehwolf]

On Mon, 20 Oct 2025 02:12:17 GMT, SendaoYan <syan at openjdk.org> wrote:

>> Hi all,
>> 
>> The sub-test failcount in jdk/internal/platform/docker/TestDockerMemoryMetrics.java requires swap memory enable on the test host. But the swap memory check introduced by JDK-8264524 do not work correctly, because it's missing jvm option '-XX:+AlwaysPreTouch', shows as below. This PR add jvm option '-XX:+AlwaysPreTouch' to make the swap memory check work correctly, and use jtreg.SkippedException instead of print waring when this test can not execute.
>> 
>> Change has been verified locally on linux-x64. Test fix only, no risk.
>> 
>> 
>>> free -h
>> total used free shared buff/cache available
>> Mem: 751Gi 513Gi 229Gi 5.0Mi 8.4Gi 234Gi
>> Swap: 0B 0B 0B
>> 
>> 
>> Without jvm option -XX:+AlwaysPreTouch, the 'java -Xms128m -Xmx128m -version' can start successfully:
>> 
>>> docker run --rm --memory=128m jdk-internal:test-jdk-internal-platform-docker-TestDockerMemoryMetrics-metrics-memory /jdk/bin/java -Xms128m -Xmx128m -version
>> openjdk version "26" 2026-03-17
>> OpenJDK Runtime Environment HJDK-0 (build 26+-42b2999c)
>> OpenJDK 64-Bit Server VM HJDK-0 (build 26+-42b2999c, mixed mode, sharing)
>> 
>> 
>> With jvm option -XX:+AlwaysPreTouch, the 'java -XX:+AlwaysPreTouch -Xms128m -Xmx128m -version' can not start and killed by docker(return code is 137):
>> 
>>> docker run --rm --memory=128m jdk-internal:test-jdk-internal-platform-docker-TestDockerMemoryMetrics-metrics-memory /jdk/bin/java -XX:+AlwaysPreTouch -Xms128m -Xmx128m -version ; echo $?
>> 137
>
> SendaoYan has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update the comments

Looks OK to me.

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Marked as reviewed by sgehwolf (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27823#pullrequestreview-3355132735