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katepl
katepl
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Pinned topic Occasionall long gc run

‏2010-03-12T16:39:24Z |
After some analysis with IBM's Garbage Collection and Memory Visualizer 2.4.0 I've discovered long gc pauses happen from time to time.
My application is a multithreaded webapp on tomcat 5.5 with axis1 running on java5 sr9.
After my webapp is heavily loaded for few hours a single gc happens that runs for very long time. Every other gc before and after runs in time of miliseconds and the long one lasts for tens of seconds.

Do you know what may be cause of such long pauses excluding heavy system overload by other processes?

My parameters are:
-Xms64m -Xmx512m -Xgcpolicy:gencon -Xss1m

One sample from -verbose:gc:

<af type=
"nursery" id=
"11143" timestamp=
"Mar 12 09:41:58 2010" intervalms=
"164.194"> <minimum requested_bytes=
"528" /> <time exclusiveaccessms=
"0.196" /> <nursery freebytes=
"0" totalbytes=
"42720256" percent=
"0" /> <tenured freebytes=
"56518032" totalbytes=
"401486848" percent=
"14" > <soa freebytes=
"56518032" totalbytes=
"401486848" percent=
"14" /> <loa freebytes=
"0" totalbytes=
"0" percent=
"0" /> </tenured> <gc type=
"scavenger" id=
"11142" totalid=
"11379" intervalms=
"165.568"> <expansion type=
"tenured" amount=
"5768192" newsize=
"407255040" timetaken=
"5.607" reason=
"continue current collection" /> <flipped objectcount=
"63312" bytes=
"2637580" /> <tenured objectcount=
"212556" bytes=
"14387780" /> <refs_cleared soft=
"0" weak=
"186" phantom=
"0" /> <finalization objectsqueued=
"0" /> <scavenger tiltratio=
"65" /> <nursery freebytes=
"41128416" totalbytes=
"44057088" percent=
"93" tenureage=
"1" /> <tenured freebytes=
"47189832" totalbytes=
"407255040" percent=
"11" > <soa freebytes=
"47189832" totalbytes=
"407255040" percent=
"11" /> <loa freebytes=
"0" totalbytes=
"0" percent=
"0" /> </tenured> <time totalms=
"46745.808" /> </gc> <nursery freebytes=
"41127888" totalbytes=
"44057088" percent=
"93" /> <tenured freebytes=
"47189832" totalbytes=
"407255040" percent=
"11" > <soa freebytes=
"47189832" totalbytes=
"407255040" percent=
"11" /> <loa freebytes=
"0" totalbytes=
"0" percent=
"0" /> </tenured> <time totalms=
"46747.306" /> </af>


or another one


<af type=
"nursery" id=
"20602" timestamp=
"Mar 11 10:15:16 2010" intervalms=
"368.863"> <minimum requested_bytes=
"528" /> <time exclusiveaccessms=
"0.178" /> <nursery freebytes=
"0" totalbytes=
"47200256" percent=
"0" /> <tenured freebytes=
"25464528" totalbytes=
"237072384" percent=
"10" /> <gc type=
"scavenger" id=
"20601" totalid=
"22267" intervalms=
"369.960"> <flipped objectcount=
"160747" bytes=
"6310572" /> <tenured objectcount=
"66298" bytes=
"2735960" /> <refs_cleared soft=
"0" weak=
"40" phantom=
"0" /> <finalization objectsqueued=
"0" /> <scavenger tiltratio=
"74" /> <nursery freebytes=
"42930608" totalbytes=
"49806848" percent=
"86" tenureage=
"2" /> <tenured freebytes=
"22480848" totalbytes=
"237072384" percent=
"9" /> <time totalms=
"16356.601" /> </gc> <nursery freebytes=
"42930080" totalbytes=
"49806848" percent=
"86" /> <tenured freebytes=
"22480848" totalbytes=
"237072384" percent=
"9" /> <time totalms=
"25615.054" /> </af>


Thanks in advance,
Kate