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From Stack <st...@duboce.net>
Subject Re: CMF & NodeIsDeadException
Date Mon, 03 Jan 2011 22:05:03 GMT
On Mon, Jan 3, 2011 at 12:50 PM, Wayne <wav100@gmail.com> wrote:
> We have an 8GB heap. What should newsize be? I just had another node die
> hard after going into a CMF storm. I swear it had solid CMFs 30+ in a row.

Did a full stop-the-world GC run in between?  It should have cleaned
up fragmentation.

> I have no idea what eden space is or how to see what it is. ??

Sorry.  There's a bunch of 'cute' terms used for describing the two
heap areas in the JVM.  Basically, new stuff goes into the 'new' or
'eden' area first.  If it sticks around through N (configurable) GCs,
it gets promoted to old or tenured generation (there are other names
for these notions of young and old).  The garbage collection
algorithms done in the two heaps differ.  See the Ted citation for
more on the gruesome details (though come up to a newer version of
that doc).  The JVM is supposed to work ergonomically but it just
ain't smart enough dealing w/ HBase/Cass loadings it seems (e.g. it
keeps growing the new/eden space pathologically it would seem).

> Not knowing what else to do I will start using some of the Cassandra
> settings I used to improve it by setting the occupancy fraction. Any other
> ideas???

Which config. you talking of? -XX:+CMSInitiatingOccupancyFraction?
Thats a good one to toggle down from defaullts.  Should help put off
promotion failures a while.


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