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From sridhar basam <...@basam.org>
Subject Re: mutator.execute() timings - big variance noted - pointers needed on understanding/improving it
Date Thu, 10 Mar 2011 16:08:54 GMT
Sounds like GC from your description of fast->slow->fast. Collect GC times
from both the client and server side and plot against your application
timing.

 If you uncomment the verbose GC entries in the cassandra-env.sh file you
should get timing for the server side, pass in the same arguments for your
client. Align time across the 3 files and plot to see if GC is the cause.

 Sridhar



On Thu, Mar 10, 2011 at 9:30 AM, Roshan Dawrani <roshandawrani@gmail.com>wrote:

> Hi,
>
> I am in the middle of some load testing on a 1-node Cassandra setup. We are
> not on very high loads yet. We have recorded the timings taken up by
> mutator.execute() calls and we see this kind of variation during the test
> run:
>
> So, 25% of the times, execute() calls come back in 25 milli-seconds, but
> the longer calls go upto 4 seconds.
>
> Can someone please provide some pointers on what and where to focus on in
> my Hector / Cassandra setup? We are mostly on the default Cassandra
> configuration at this time - only change is the max connection pool size
> (CassandraHostConfigurator.maxActive) is changed to 300 from a default of
> 50.
>
> I would also like to add that the time increase is not linear - it starts
> fast, goes, slow, very slow, and becomes faster again.
>
> ------------------------
>   25%     29
>   50%    105
>   66%    185
>   70%    208
>   75%    240
>   80%    297
>   90%    510
>   95%    854
>   98%   1075
>   99%   1215
>  100%   4442
> ------------------------
>
> --
> Roshan
> Blog: http://roshandawrani.wordpress.com/
> Twitter: @roshandawrani <http://twitter.com/roshandawrani>
> Skype: roshandawrani
>
>

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