RFR: 8350854: Include thread counts in safepoint logging [v2]

[David Holmes]

On Tue, 4 Mar 2025 19:45:33 GMT, Xiaolong Peng <xpeng at openjdk.org> wrote:

>> The PR is to add thread counts in safepoint logging. In recent work, we notice the number of Java thread may affects time to reach/leave safepoint hardly in some cases, but safepoint logging doesn't have thread counts, thread counts are printed only with 'safepoint+stats' log. 
>> 
>> Given in many cases, we only have `safepoint` log enabled, not `safepoint+stats`, it make sense to add thread count to 'safepoint' logging. 
>> 
>> Here is example log output with the change:
>> 
>> [15.240s][info][safepoint      ] Safepoint "ShenandoahFinalMarkStartEvac", Time since last: 3527459 ns, Reaching safepoint: 78666 ns, At safepoint: 821625 ns, Leaving safepoint: 1472167 ns, Total: 2372458 ns, Threads: 3 runnable, 1038 total
>> 
>> 
>> 
>> ### Test
>> - [x] Tire1
>> - [x] Tire2
>
> Xiaolong Peng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Use format %d instead of INT32_FORMAT

LGTM. Thanks

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23838#pullrequestreview-2659973145