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From Robert Wille <>
Subject Re: High CPU usage on some of nodes
Date Thu, 10 Sep 2015 13:27:41 GMT
It sounds like its probably GC. Grep for GC in system.log to verify. If it is GC, there are
a myriad of issues that could cause it, but at least you’ve narrowed it down.

On Sep 9, 2015, at 11:05 PM, Roman Tkachenko <> wrote:

> Hey guys,
> We've been having issues in the past couple of days with CPU usage / load average suddenly
skyrocketing on some nodes of the cluster, affecting performance significantly so majority
of requests start timing out. It can go on for several hours, with CPU spiking through the
roof then coming back down to norm and so on. Weirdly, it affects only a subset of nodes and
it's always the same ones. The boxes Cassandra is running on are pretty beefy, 24 cores, and
these CPU spikes go up to >1000%.
> What is the best way to debug such kind of issues and find out what Cassandra is doing
during spikes like this? Doesn't seem to be compaction related as sometimes during these spikes
"nodetool compactionstats" says no compactions are running.
> Thanks!

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