Fwd: negative pause times

[Angelika Langer]

Thanks for the hint.

The negative pause times appeared in a GC traces that a colleague gave
us to share his experiences with G1.  It was produced on Linux and quite 
possibly using VMware.  So, your hint helps explaining the negative 
pause time.  Thank you.

Whether it is worth a bug report we do not know.  The question is: does
the time drift affect G1 and its algorithms?  After all, the collector
gathers statistics in order to figure out how long the next gc pause
will be.  It must take time stamps for this purpose.

Does G1 work reliably in a situation with time drift problems?

Angelika

>> Does anybody know off hand why the G1 log file shows negative pause
times?
>>
>>
>> 222.121: [GC pause (young) 561M->528M(1005M), 0.0586070 secs]
>> 222.915: [GC pause (young) 576M->540M(1005M), 0.0447820 secs]
>> 223.763: [GC pause (young) 602M->562M(1005M), -0.7354870 secs]  <=======
>> 225.572: [GC pause (young) 772M->632M(1005M), 0.0719350 secs]
>>
>
> Is this on Linux? Are you running NTP or otherwise causing TOD to
> be adjusted? (you might want to turn off NTP if the negative times
> bother you.) Are you running on VMware? (try a non-virtualized
> run to see if the problem reproduces.) The negative pause times
> we have seen in the past have usually been related to one of the
> other of the above.
>
> Please file a formal bug using your support credentials should
> you believe this is an issue that needs delving deeper, especially
> if you have a usable test case.