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From Rob Coli <>
Subject Re: cassandra 1.0.8 memory usage
Date Thu, 11 Oct 2012 18:02:16 GMT
On Wed, Oct 10, 2012 at 11:04 PM, Daniel Woo <> wrote:
> I am running a mini cluster with 6 nodes, recently we see very frequent
> ParNewGC on two nodes. It takes 200 - 800 ms on average, sometimes it takes
> 5 seconds. You know, hte ParNewGC is stop-of-wolrd GC and our client throws
> SocketTimeoutException every 3 minutes.

What version of Cassandra? What JVM? Are JNA and Jamm working?

> I checked the load, it seems well balanced, and the two nodes are running on
> the same hardware: 2 * 4 cores xeon with 16G RAM, we give cassandrda 4G
> heap, including 800MB young generation. We did not see any swap usage during
> the GC, any idea about this?

It sounds like the two nodes that are pathological right now have
exhausted the perm gen with actual non-garbage, probably mostly the
Bloom filters and the JMX MBeans.

> Then I took a heap dump, it shows that 5 instances of JmxMBeanServer holds
> 500MB memory and most of the referenced objects are JMX mbean related, it's
> kind of wired to me and looks like a memory leak.

Do you have a "large" number of ColumnFamilies? How large is the data
stored per node?


=Robert Coli
YAHOO - rcoli.palominob
SKYPE - rcoli_palominodb

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