RFR: 8359104: gc/TestAlwaysPreTouchBehavior.java#<gcname> fails on Linux [v3]

[Albert Mingkun Yang]

On Thu, 11 Sep 2025 14:32:19 GMT, Andreas Steiner <asteiner at openjdk.org> wrote:

>> Get accurate RSS, from smaps_rollup if available(Linux >= 4.14), because the RSS from status is inaccurate especially on systems with more than 32 CPUs.
>> 
>> Not sure if all the additional meminfos like the Pss, Pss_dirty, Pss_Anon, Pss_File, Pss_Shmem, Swap and SwapPss are really needed too. But can be perhaps helpful too.
>> 
>> As the inaccurate memory infos are still used in other methods:
>> - [print_process_memory_info()](https://github.com/openjdk/jdk/blob/385c13298932f1de16e6161652be35d966d822ec/src/hotspot/os/linux/os_linux.cpp#L2393)
>> - [jfr_report_memory_info()](https://github.com/openjdk/jdk/blob/385c13298932f1de16e6161652be35d966d822ec/src/hotspot/os/linux/os_linux.cpp#L2686)
>> - [trim_native_heap()](https://github.com/openjdk/jdk/blob/385c13298932f1de16e6161652be35d966d822ec/src/hotspot/os/linux/os_linux.cpp#L5376)
>> 
>> one can think about to use the accurate values there too.
>
> Andreas Steiner has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Changed num_found and num_values to size_t, do the null-check right after the fopen and return early, eliminated the variable shadowing of info

Marked as reviewed by ayang (Reviewer).

src/hotspot/os/linux/os_linux.cpp line 2395:

> 2393:          (info->pssshmem == -1   && sscanf(buf, "Pss_Shmem: %zd kB", &info->pssshmem) == 1) ||
> 2394:          (info->swap == -1       && sscanf(buf, "Swap: %zd kB", &info->swap) == 1) ||
> 2395:          (info->swappss == -1    && sscanf(buf, "SwapPss: %zd kB", &info->swappss) == 1)

I'd probably align `== -1 &&` and `==1)`.

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PR Review: https://git.openjdk.org/jdk/pull/27192#pullrequestreview-3212076914
PR Review Comment: https://git.openjdk.org/jdk/pull/27192#discussion_r2341228607