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From Colin Vipurs <zodiac...@gmail.com>
Subject Too many ParNew's
Date Sat, 05 Jun 2010 17:23:16 GMT
I'm seeing lots of ParNew messages which is affected performance,
along the lines of:

 INFO 17:54:18,567 GC for ParNew: 1522 ms, 69437384 reclaimed leaving 979692384
used; max is 4424663040
 INFO 17:54:22,567 GC for ParNew: 1989 ms, 69323576 reclaimed leaving 981439840
used; max is 4424663040
 INFO 17:54:26,187 GC for ParNew: 1337 ms, 69447160 reclaimed leaving 983903040
used; max is 4424663040
 INFO 17:54:29,489 GC for ParNew: 861 ms, 69507336 reclaimed leaving 986200344 u
sed; max is 4424663040
 INFO 17:54:32,238 GC for ParNew: 954 ms, 69245912 reclaimed leaving 987667920 u
sed; max is 4424663040
 INFO 17:54:36,053 GC for ParNew: 1242 ms, 69501648 reclaimed leaving 989972496
used; max is 4424663040

and this is affecting performance.

This is on an 8Gb 4xCore machine with a 4Gb heap and mmapped i/o.
KeyCaches are set to defaults and RowCaches are turned off.

If I flush, then restart cassandra these go away and performance goes
back to a decent level for a certain time until these crop up again.
Obviously this is something to do with memory pressure but I'm not
sure what.  When I restart the node I presume that more requests are
hitting the disk, but from a client perspective this ends up giving
much better performance than when under the GC storm.  Are there some
settings I can tweak to ensure this doesn't happen and perhaps direct
more queries to disk?

-- 
Maybe she awoke to see the roommate's boyfriend swinging from the
chandelier wearing a boar's head.

Something which you, I, and everyone else would call "Tuesday", of course.

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