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From Ryan King <r...@twitter.com>
Subject Re: Ran into an issue where Cassandra Crashed when running out of heap space
Date Tue, 20 Jul 2010 20:33:03 GMT
On Tue, Jul 20, 2010 at 1:28 PM, Peter Schuller
<peter.schuller@infidyne.com> wrote:
>> Attaching Jconsole shows that there is a growth of memory and weird
>> spikes. Unfortunately I did not take a screen shot of the growth of
>> the spike over time. I'll do that when it occurs again.
>
> Note that expected behavior for CMS is to have lots of small ups and
> downs as a result of young generation GC:s, and a longer period cycle
> of larger ups and downs that correspond to CMS kicking in with a
> concurrent mark/sweep phase.
>
> To get a reasonable estimate of the actual live set, you would
> normally look at the free memory at the end of one of the larger dips
> after a CMS mark/sweep phase.

You'll also see memory sawtoothing for memtable growth+flush cycles.

-ryan

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