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

[Thomas Stuefe]

On Tue, 1 Nov 2022 12:31:02 GMT, Thomas Stuefe <stuefe 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
>
> Does this really have to be a product switch? The JBS issue sounds like it is not even clear if polling the metrics is actually the culprit. How about a debug-only switch, or at least a diagnostic product switch?

> @tstuefe if the option is DIAGNOSTIC then I don't need CSR, right?

Exactly :)

-------------

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