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From Yang <>
Subject performance diagnosis questions
Date Fri, 09 Sep 2011 21:21:36 GMT
I'm trying to understand where my queries are spending their time,

trying yourkit , vmstat, iostat -x,  plus trial and error by
enabling/disabling some features

my application basically creates a lot of entries for "user history",
where each history is a row, and
is maintained to be less than 20 items long,  the application
continuously creates new history and queries the history
set with some key.

as the application goes on, it became slower.

somehow if I shutdown Cassandra and restart, it seems to go faster. I
can't understand why this could be the case, with my
limited understanding of Cassandra. any possible reasons?

also I'm seeing a bunch of vmstat swap in and swap outs, about 10% of
the time.  just want to make sure: if a Mmapped RandomAccessFile loads
a block into memory, that would also show up in "swap in" count,
right? ---- so far I've not enabled the
JVM heap lock yet. will try that

Thanks  a lot

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