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From David Hawthorne <dha...@gmx.3crowd.com>
Subject nodetool meminfo
Date Sat, 22 Sep 2012 19:51:38 GMT
I'm looking for information on where my memory is going.  Specifically, I'd like to be able
to tune my memtable and row/key cache sizes, and anything else that can be quantified and
configured.  To that end, what I'd like to see is the current row cache memory used / total
allowed by configuration, current key cache memory used / total allowed by configuration,
current memory used by memtables / total allowed by configuration, and any other data structures
that might help me or more advanced cassandra operations gurus quickly troubleshoot and identify
obvious problems.

This problem came about because my row cache was using too much memory and the first indication
of this was that the cluster stopped doing work and the logs were full of communication errors
to other hosts and CMS entries.  A "nodetool meminfo" command would have made the problem
more obvious just by showing me that the row cache + key cache + memtables was already very
close to my heap limit.  I imagine this will also be useful with the 1.1.x versions where
a global row cache size can be configured because it's still going to be nice to see if a)
it's full, and b) it can be increased based on current heap limit, memtable usage, etc.
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