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From Robert Coli <rc...@eventbrite.com>
Subject Re: Cassandra heap pre-1.1
Date Wed, 05 Nov 2014 20:10:34 GMT
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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