http://www.datastax.com/support-forums/topic/seeing-memory-swap-issue-on-cassandra-nodes Software, Support, and Training for Apache Cassandra en-US Thu, 20 Jun 2013 00:24:26 +0000 http://bbpress.org/?v=1.0.3 q http://www.datastax.com/support-forums/search.php http://www.datastax.com/support-forums/topic/seeing-memory-swap-issue-on-cassandra-nodes#post-8161 Thu, 27 Dec 2012 17:10:38 +0000 Sven 8161@http://www.datastax.com/support-forums/ <p>Has reducing the max heap size resolved the swapping issue?</p> <p>Keep in mind that C* uses off heap memory as well to store cache data. You may want to look into tuning that, see here <a href="http://www.datastax.com/docs/1.1/operations/tuning" rel="nofollow">http://www.datastax.com/docs/1.1/operations/tuning</a> for more detail.</p> <p>With respect to the high memory usage reported for the Cassandra process, check here: <a href="http://wiki.apache.org/cassandra/FAQ#mmap" rel="nofollow">http://wiki.apache.org/cassandra/FAQ#mmap</a>.</p> <p>With respect to the high cached value. That is a Linux'ism, it is the OS level cache for file reads (see here for more information: <a href="http://egloo.wordpress.com/2008/10/29/linux-cached-memory/)" rel="nofollow">http://egloo.wordpress.com/2008/10/29/linux-cached-memory/)</a>. It should not interfere with normal operations as it will only use unused memory. To find out what processes are actually using swap (in case that is still an issue after tuning the JVM and C*), check here <a href="http://stackoverflow.com/questions/479953/how-to-find-out-which-processes-are-swapping-in-linux" rel="nofollow">http://stackoverflow.com/questions/479953/how-to-find-out-which-processes-are-swapping-in-linux</a>. I would expect that to be C*, but with some tuning you should be able to reduce swap use.</p> <p>Thanks,<br /> Sven </p> http://www.datastax.com/support-forums/topic/seeing-memory-swap-issue-on-cassandra-nodes#post-8139 Wed, 26 Dec 2012 20:11:24 +0000 srk_user 8139@http://www.datastax.com/support-forums/ <p>Any update on this? </p> http://www.datastax.com/support-forums/topic/seeing-memory-swap-issue-on-cassandra-nodes#post-8047 Fri, 21 Dec 2012 03:01:19 +0000 srk_user 8047@http://www.datastax.com/support-forums/ <p>I changed the MAX_HEAP_SIZE to "4G" and restarted the nodes. On Opscenter, when I check the OS:memory for each node, I see 4GB of used memory but cached memory is over 7GB and seems to growing.. My question is how do I control the cached memory? </p> http://www.datastax.com/support-forums/topic/seeing-memory-swap-issue-on-cassandra-nodes#post-8030 Thu, 20 Dec 2012 14:45:00 +0000 srk_user 8030@http://www.datastax.com/support-forums/ <p>We are seeing memory swap issues on cassandra nodes. We are running DataStax Enterprise 2.1.1. Each node with 6CPU 16GB memory. </p> <p>The heap is setup as follows</p> <p>MAX_HEAP_SIZE="8G"<br /> HEAP_NEWSIZE="800M"</p> <p>Here's what we are seeing on the server.. Any idea why we are seeing the swap issue and how can we resolve it</p> <p>top - 09:43:06 up 36 days, 19:25, 1 user, load average: 0.00, 0.03, 0.02<br /> Tasks: 169 total, 1 running, 168 sleeping, 0 stopped, 0 zombie<br /> Cpu(s): 0.2%us, 0.1%sy, 0.0%ni, 96.6%id, 3.0%wa, 0.0%hi, 0.0%si, 0.0%st<br /> Mem: 16435996k total, 15833124k used, 602872k free, 465808k buffers<br /> Swap: 2068400k total, 2068356k used, 44k free, 5466128k cached</p> <p> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND<br /> 4479 casadmin 23 0 268g 12g 3.9g S 0.7 78.8 5595:34 /usr/java/jre1.6.0_29/bin/java -ea -javaagent:/opt/nosql/dse-2.1.1/resources/cassandra/lib/jamm-0.2.5.jar -<br /> 21326 sr88197 15 0 12756 1180 844 R 0.7 0.0 0:00.01 top<br /> 31548 casadmin 18 0 507m 114m 9580 S 0.7 0.7 184:30.81 /usr/java/jre1.6.0_29/bin/java -Xmx40M -Xms40M -Djavax.net.ssl.trustStore=ssl/agentKeyStore -Djavax.net.ssl </p>