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Re: jboss cpu spike - GC?
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created by <a href="https://community.jboss.org/people/nikhilmone">Nikhil Mone</a> in <i>Performance Tuning</i> - <a href="https://community.jboss.org/message/778836#778836">View the full discussion</a>
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<div class="jive-rendered-content"><blockquote class="jive-quote"><p>jboden wrote:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Hi,</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I have a jboss 5.1 app with sun jdk 1.7.something. At night, it runs a large job and gobbles memory. The process gets to 2.5GB and never goes down, but I hear that's normal with heap space? But after a few days of this, I begin to see the cpu spike to 100% of one cpu for a few seconds, then go down. This happens every 5 seconds or so, probably GC?</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Using mostly a default run.bat, I have the jvm args set to:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>-Xrs -Xms256M -Xmx2048M -XX:MaxPermSize=256m -XX:+CMSClassUnloadingEnabled -XX:+UseConcMarkSweepGC </p><p> -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000</p><p> -Dorg.jboss.resolver.warning=true</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Should we be doing something more specific? And if the GC keeps running that often even after the thread to do the nightly job has ended, do I have a memory leak somewhere? We do sometimes run out of memory, but maybe it needs Xmx of 4gb just to finish the job. </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I'm going to up the memory anyway, but what clues do we look for to determine if there is a leak and/or better GC settings?</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>Thank you very much!</p><p>Jim</p></blockquote><p>You can try adding below JAVA options in your "run.bat" to analyse what's wrong with GC :</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p><code> -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStamps </code><code>-Xloggc:<location of log directory>\gc.log</code></p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>"gc.log" will contain the information about the collections, if you see a lot of gc activity (mostly FULL GC) when the issue occurs, then you would need to tune your memory/gc settings.</p></div>
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