Long GC pauses; full gc eventually takes 30 secs. (from Developer Forums)

Question

from http://forum.java.sun.com/thread.jspa?threadID=5145522
jre 1.5.0_06,
-Dcom.sun.management.jmxremote -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintTenuringDistribution -XX:NewRatio=3 -XX:MaxTenuringThreshold=3 -XX:NewSize=90M -XX:MaxNewSize=90M -Xmx800M
windows 2003 server
normally, full gc's occur with < 1 second durations, but eventually, the duration peaks at 30 seconds, then 7 seconds, then back to normal
the heap was at about 290MB (far from full).
setting maxgcpausemillis has no effect (something extraordinary happens?)
there is no obvious pattern in the long pauses (not due to perm resizing or so)
does anyone have experience with sudden long pauses?
we could think of heap being swapped - but we don't know how to monitor this (and nobody was starting memory consuming applications at the time)
does anyone know how we best monitor swapping on a windows?
we are not able to use CMS immediately without testing for a period (had crashes due to http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6386633)
here are samples of long pauses
here are some long pauses (days apart - the gc log is embedded in our own loggings)
061221 102753 0750 EV coreservice.taskoutput.container 75.537: [GC [PSYoungGen: 70133K->19827K(53632K)] 173056K->138149K(172736K), 11.5205585 secs] ##[
070301 122542 0812 EV coreservice.taskoutput.container 6146.116: [Full GC [PSYoungGen: 768K->0K(90944K)] [PSOldGen: 286976K->213826K(259328K)] 287744K->213826K(350272K) [PSPermGen: 19432K->19432K(23040K)], 30.1171480 secs] ##[
070305 163701 0140 EV coreservice.taskoutput.container [PSYoungGen: 1256K->0K(90176K)] [PSOldGen: 239309K->197132K(221632K)] 240565K->197132K(311808K) [PSPermGen: 19260K->19039K(23808K)], 20.3872070 secs] ##[
tak!
/aksel

Answer 1

does anyone know how we best monitor swapping on awindows?I not sure if this is the best.
You can use ctrl-shift-escape. Click on the processes tab and then goto the menu: View->Select Columns... and add "Page Fault Delta" column. I would also suggest you add the VM Memory size column too.