RFR: Use timed wait to sleep control thread

[earthling-amzn]

On Wed, 7 Apr 2021 17:20:54 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Using a timed `wait` rather than a naked sleep allows the control thread to be more responsive to requests from mutators and the regulator thread to start GC cycles. The sleep time is also changed from `ShenandoahControlIntervalMin` to `ShenandoahControlIntervalMax` to reduce unnecessary polling cycles. We could use a plain `wait`, but the control thread is responsible for periodically sending allocation metrics to the `pacer`.
>
> src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp line 374:
> 
>> 372:       // The timed wait is necessary because this thread has a responsibility to send
>> 373:       // 'alloc_words' to the pacer when it does not perform a GC.
>> 374:       MonitorLocker lock(&_control_lock, Mutex::SafepointCheckFlag::_no_safepoint_check_flag);
> 
> This is just `Mutex::_no_safepoint_check_flag`, Hotspot uses that everywhere. Another instance in also in the same file.

Sorry, my IDE does this. Fixed.

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PR: https://git.openjdk.java.net/shenandoah/pull/28