RFR: 8299858: [Metrics] Swap memory limit reported incorrectly when too large [v3]

[Severin Gehwolf]

On Wed, 25 Jan 2023 13:05:06 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains one commit:
>> 
>>   8299858: [Metrics] Swap memory limit reported incorrectly when too large
>
> src/java.base/linux/native/libjava/CgroupMetrics.c line 45:
> 
>> 43:     jlong pages = sysconf(_SC_PHYS_PAGES);
>> 44:     jlong page_size = sysconf(_SC_PAGESIZE);
>> 45:     return pages * page_size;
> 
> Preexisting, and theoretical nitpickery: I got curious when I saw this. What does sysconf return if a 32-bit VM runs on a large machine with >8Tb main memory and 4k pages? In that case, _SC_PHYS_PAGES would overflow the 32-bit long return type of sysconf.

Yes. Any suggestions as to how to fix it? This code was actually changed recently with [JDK-8300119](https://bugs.openjdk.org/browse/JDK-8300119). Anyway, this should go into a separate bug if we change it. Do you agree?

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PR: https://git.openjdk.org/jdk/pull/12118