RFR(S): 8230126: delay_to_keep_mmu can delay shutdown

[sangheon.kim at oracle.com]

Hi Kim,

On 8/27/19 12:22 PM, Kim Barrett wrote:
> Please review this change to G1ConcurrentMarkThread::delay_to_keep_mmu
> to use a wait-with-timeout on CGC_lock rather than os::sleep to
> implement the delay.  This allows the delay to be terminated early by
> a thread termination request.
>
> Also fixed a units bug in the calculation of the delay.  The call to
> G1MMUTracker::when_ms was with "now" in seconds and "prediction" in
> milliseconds.  This function expects both arguments to be in seconds,
> and returns a millisecond result.  This bug was largely masked by the
> calculation first clipping the prediction value to the max GC time.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8230126
>
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8230126/open.00/
Couldn't always use 'ms'?
I think 'os::elapsedTime() * 1000' seems simpler instead of 'ms -> sec 
-> ms' conversion and may remove ceil() call.

Thanks,
Sangheon


>
> Testing:
> mach5 tier1-3
>
> Locally (linux-x64) ran gcbasher test with some additional logging
> added to the changed functions to verify the various values looked
> okay.
>