-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 James,
On 6/20/12 12:27 PM, James Lampert wrote: > We just had a report of extremely high CPU usage from the Tomcat > job on one of our customer installations. A WRKACTJOB screen shot > from before we forcibly shut Tomcat down and restarted it shows: > > Subsystem/Job Type CPU % Function Status CATALINA > BCH .0 CMD-QSH TIMW QP0ZSPWT BCI 112.2 > JVM-org.apache TIMW (QP0ZSPWT being the system-generated job > that's doing the actual work for the CATALINA job.) > > Of particular interest is that, at least at the moment the screen > shot was taken, the QP0ZSPWT job was taking up what appears to be > more than an entire processor, even though it's in a "time-wait" > state. > > Based on a Google search on "tomcat 7 high cpu usage," I'm > suspecting a previously unknown tightloop in our application (which > was what I suspected even before I did the Google search). The > pages I looked at also said something about profiling and thread > dumps, to find the offending thread, but since the job has been > terminated and restarted, and is not currently malfunctioning, I > wouldn't be able to do so even if I knew how (which at present I > don't). > > I've passed on the log files generated by our application itself > to someone better equipped to deal with them than I, and I've asked > the Java-400 List at Midrange.com about AS/400-specific steps to > track down the offending thread if the problem is observed again, > but I would also value any insights this list might offer. The advice you got about thread dumps was spot-on: get yourself a thread dump [1] whenever you think your process is using too much CPU time. Better yet, take a few of them and compare. If you do have a tight loop, you'll probably be able to see it because one thread will be stuck in the same method for a while. Taking a thread dump *should* be easy (not sure on AS/400) and it doesn't take a long time to get one. That means you don't disturb current users like taking a heap dump would (heap dumps in my experience tend to pause the entire JVM). I suppose you're about to take-down the JVM so user inconvenience isn't a huge deal. You might also consider that high CPU usage isn't necessarily bad, unless it's impacting the operation of one or more services. Assuming that your suspected-tight-loop finally completes, it might be better to just let it finish rather than taking-down the JVM entirely. - -chris [1] http://wiki.apache.org/tomcat/HowTo#How_do_I_obtain_a_thread_dump_of_my_running_webapp_.3F -----BEGIN PGP SIGNATURE----- Version: GnuPG/MacGPG2 v2.0.17 (Darwin) Comment: GPGTools - http://gpgtools.org Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk/rTZEACgkQ9CaO5/Lv0PDL5wCgu683MJwUBQzgn2HKPcDinUEF PyYAnAvPWYtbSB8PiKF4OfFchPKbMTcL =ETGk -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
