Troubleshooting a ~40-second minor collection

[Aaron Daubman]

Hi All,

I have unfortunately lost my GC log file (server restarted shortly after
the event) but have AppDynamics stats.

I am running Solr 3.6.1 in a jetty 9 container under jdk 1.7u25.

Max heap is 16G. <7G were used at the time of the event. Typical heap usage
is ~28%.

There were around 10 minor collection events (fairly typical) during the
minute the event occurred. The event was an almost 40-second max minor
collection time.

Around that time JVM Heap utilization was only between 27%-31% utilized - I
cannot remember the last time we had a major collection, and I have also
never seen such a long minor collection time. There is nothing I can see
about traffic to the JVM that appeared abnormal.

I did see some long external (JDBC) query times about this time as well,
but thought they were more likely a symptom of the minor collection pause,
rather than a cause.

AppDynamics monitors Code Cache,  G1 Eden Space, G1 Old Gen, G1 Perm Gen,
and G1 Survivor - the max of which at the time was Perm Gen at only 60%.

Is there anything else I can do (without the GC log file) to try and
determine the cause of the unexpected 40s minor collection pause time?

Thanks,
     Aaron
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