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From Mikio Braun <mi...@cs.tu-berlin.de>
Subject Re: Follow-up post on cassandra configuration with some experiments on GC tuning
Date Thu, 02 Sep 2010 16:38:33 GMT
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Hi Carsten,

> In this regard, what I personally miss in Mikios - however nice - analysis, is what are
the effects on the application stop times due to any garbage collection runs for the cases
tested. In most cases, I prefer having low pauses due to any garbage collection runs and don't
care too much about the shape of the memory usage, and I guess, that's the reason why the
low pause collector is used by default for running cassandra.

I see your point. I haven't explicitly tested those pauses. You can get
them from the gc logs (with some amount of perl parsing).

Subjectively speaking, I saw a higher probability of timeouts if GC took
too long. One other thing to look out for would be CMS failures (when
you start a CMS cycle but the young generation GCs run out of memory to
promote objects) which then results in a full GC cycle.

Probably I can rerun the tests and save the gc logs as well and put them
somewhere.

- -M


- -- 
Dr. Mikio Braun                        email: mikio@cs.tu-berlin.de
TU Berlin                              web: ml.cs.tu-berlin.de/~mikio
Franklinstr. 28/29                     tel: +49 30 314 78627
10587 Berlin, Germany



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