RFR: 8315149: Add hsperf counters for CPU time of internal GC threads [v33]

[Jonathan Joo]

On Fri, 27 Oct 2023 14:00:43 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

> Okay, these counters can be accessed frequently, but is it necessary for them to provide up-to-date information on every access? If not, what level of delay is acceptable? I assume this depends on how often AHS resizes the heap. (In the Parallel case, I believe the counters can be outdated for the duration of the full-gc.)

The way AHS is implemented, we access these counters upon every heap resize, so in theory every call to `expand()` and `shrink()` will rely to some extent on these counters. If the counters do happen to be stale, AHS won't break, but will certainly be less effective.

For the rest of the points, Man do you have any additional insight?

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PR Comment: https://git.openjdk.org/jdk/pull/15082#issuecomment-1786197139