Strange STW pauses

[Nick Chadwick]

Thanks both for your replies.

Yes, it is a recurring issue - it doesn't go away after the JVM has warmed
up. I am able to trigger the pauses quite easily and regularly with minimal
load.

I am already logging GC in addition, but there are no GCs close to the
pauses that I am seeing. As I understand it, the log entries above are
explicitly not garbage collections - they would show something other than
"no vm operation" under vmop (e.g. CollectForMetadataAllocation,
ParallelGCFailedAllocation, etc) - but guaranteed safepoints. I understand I
can tweak the GuaranteedSafepointInterval, but that doesn't feel like the
solution to me, and would probably just make the pauses longer, albeit less
often.

If you do think it's still worth me posting some GC logs here as well, I
can, but it definitely feels like it is not GC-related. (I am running with a
large heap, and see only a few, short pauses for GC)

Although I agree it looks like the vmop itself is not taking up the time, I
am seeing stop-the-world pauses that correlate very closely with the total
time spent under sync/cleanup in these specific pauses.

Grateful for any further insight.



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