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<a href="http://community.jboss.org/index.jspa" style="text-decoration: none; color: #E1E1E1">JBoss Community</a></h1>
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Re: Full Garbage Collection every few seconds – GC frees very little memory (JBoss 4.2.3 with JDK 1.5.0 64-bit)
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created by <a href="http://community.jboss.org/people/kopin">Constantine Pinakoulakis</a> in <i>Performance Tuning</i> - <a href="http://community.jboss.org/message/573709#573709">View the full discussion</a>
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<div class="jive-rendered-content"><p>Update:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>It seems that the problem persists even after setting NewRatio=3 with the throughupt GC.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>We therefore tried a different approach altogether by using the CMS collector (in order to minimize stop times) with the following settings on one of the servers :</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>JAVA_OPTS="-server -Xrs -Xms2048m -Xmx2048m -XX:MaxPermSize=512m -XX:NewSize=300m -XX:ThreadStackSize=160  -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:CMSInitiatingOccupancyFraction=60 -XX:+UseCMSCompactAtFullCollection -Djava.awt.headless=true -Djava.library.path=$JBOSS_NATIVE_DIR -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000"</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I had to set NewSize explicitly, since NewRatio is ignored by the CMS collector (I read a post that said it is some sort of JVM bug).</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>We noticed that during the time the server with the Throughput GC was having a "bad" run, the one with the CMS collector was healthy, although they were both under significant load.  The server with the CMS collector recovered fully and the GC was freeing a lot of memory, while the one with the throughput GC did not and had to be restarted.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>CMSInitiatingOccupancyFraction was set to 60, which is somewhat conservative; will probably need to experiment on that.</p></div>
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