RFR(S): 8230126: delay_to_keep_mmu can delay shutdown

[Kim Barrett]

> On Aug 28, 2019, at 9:16 AM, Stefan Johansson <stefan.johansson at oracle.com> wrote:
> 
> Hi Kim,
> 
> On 2019-08-27 21:22, 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/
> Looks good, thanks for fixing this.
> 
> Cheers,
> Stefan

Thanks.

> 
>> 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.