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From Raj N <raj.cassan...@gmail.com>
Subject Re: Cassandra heap pre-1.1
Date Thu, 06 Nov 2014 00:42:53 GMT
We are planning to upgrade soon. But in the meantime, I wanted to see if we
can tweak certain things.

-Rajesh

On Wed, Nov 5, 2014 at 3:10 PM, Robert Coli <rcoli@eventbrite.com> wrote:

> On Tue, Nov 4, 2014 at 8:51 PM, Raj N <raj.cassandra@gmail.com> wrote:
>
>> Is there a good formula to calculate heap utilization in Cassandra
>> pre-1.1, specifically 1.0.10. We are seeing gc pressure on our nodes. And I
>> am trying to estimate what could be causing this? Using node tool info my
>> steady state heap is at about 10GB. XMX is 12G.
>>
>
> Basically, no. If you really want to know, take a heap dump and load it
> into Eclipse Memory Analyzer.
>
>
>> I have 4.5 GB of bloom filters which I can derive looking at cfstats
>>
>
> This is a *very* large percentage of your total heap, and is probably the
> lever you have most influence on pulling.
>
>
>> I have negligible row caching.
>>
>
> Row caching is generally not advised in that era, especially with heap
> pressure.
>
>
>> I have key caching enabled on my cfs. I couldn't find an easy way to
>> estimate how much this is using, but I tried to invalidate the key cache
>> and I got 1.3 GB back.
>>
>
> Key caching is generally advisable, but 1.3GB is a lot of key cache..
>
>
>> That still only adds up to 5.8 GB. I know there is index sampling going
>> on as well. I have around 800 million rows. Is there a way to estimate how
>> much space this would add up to?
>>
>
> Plenty. You should reduce your bloom filter size, or upgrade to a version
> of Cassandra that moves stuff off the heap.
>
> =Rob
> http://twitter.com/rcolidba
>
>
>

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