RFR: 8296125: Add a command line option to set a refresh rate of the OS cached metrics in Linux [v2]

[Thomas Stuefe]

On Wed, 2 Nov 2022 00:19:35 GMT, Olga Mikhaltsova <omikhaltcova at openjdk.org> wrote:

>> I would like to add a new command line product option:
>> -XX:OsCachedMetricsRefreshRate=value, -
>> where a value is times per second and is in the range [1; 1000000000].
>> 
>> It substitutes the hardcoded timeout of 20 ms between re-readings of the OS cached metrics introduced in [JDK-8232207](https://bugs.openjdk.org/browse/JDK-8232207) and allows to set this timeout (as a refresh rate) by a user at the launch time.
>> 
>> This option will be available only on Linux.
>> 
>> It can be used as followed:
>> java -XX:OsCachedMetricsRefreshRate=100 MyApp
>
> Olga Mikhaltsova has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Made the option (OsCachedMetricsRefreshRate) DIAGNOSTIC
>  - Moved oscontainer_cache_timeout() from os::Linux to OSContainer

Please also remove OSCONTAINER_CACHE_TIMEOUT definition from osContainer_linux.hpp.

Cheers, Thomas

src/hotspot/os/linux/osContainer_linux.cpp line 68:

> 66:   return NANOSECS_PER_SEC / OsCachedMetricsRefreshRate;
> 67: }
> 68: 

I don't think the wrapper is needed, I'd just use the switch directly.

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Changes requested by stuefe (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10918