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From aaron morton <aa...@thelastpickle.com>
Subject Re: mutator.execute() timings - big variance noted - pointers needed on understanding/improving it
Date Thu, 10 Mar 2011 21:19:08 GMT
http://wiki.apache.org/cassandra/FAQ#slows_down_after_lotso_inserts

Aaron

On 11 Mar 2011, at 05:08, sridhar basam wrote:

> 
> 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
> Skype: roshandawrani
> 
> 


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