RFR: 8263236: runtime/os/TestTracePageSizes.java fails on old kernels [v3]

[Aleksey Shipilev]

On Thu, 6 May 2021 09:49:37 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> See the bug report for details. On some kernels, the madvise hint is not reflected in `/proc/smaps`. Instead, we can use a secondary evidence and read `AnonHugePages`.
>> 
>> Additional testing:
>>  - [x] Test with kernel 5.4.0 (still passes)
>>  - [x] Test with kernel 4.9.0 (used to fail, now passes)
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:
> 
>  - Merge branch 'master' into JDK-8263236-trace-page-sizes
>  - Merge branch 'master' into JDK-8263236-trace-page-sizes
>  - Merge branch 'master' into JDK-8263236-trace-page-sizes
>  - Make jcheck happy: remove the TAB
>  - 8263236: runtime/os/TestTracePageSizes.java fails on old kernels

I notice that the failures are like this with debug turned on:


>From logfile: [0.004s][info][pagesize] CodeHeap 'non-nmethods':  min=4M max=8M base=0x00007fffd9200000 page_size=2M size=8M
>From smaps: [7fffd9200000, 7fffd9600000) anonHugePages = 0 pageSize=4KB isTHP=false isHUGETLB=false



>From logfile: [0.011s][info][pagesize] Block Offset Table: req_size=2580K base=0x00007fffd7400000 page_size=2M alignment=2M size=4M
>From smaps: [7fffd7400000, 7fffd7600000) anonHugePages = 0 pageSize=4KB isTHP=false isHUGETLB=false


So these probably are not committed yet, because `-XX:+AlwaysPreTouch` (set by test) do not affect them. (sighs)

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PR: https://git.openjdk.java.net/jdk/pull/3415