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From: Daniel Doubleday <daniel.doubleday@gmx.net>
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Subject: Increase flush writer queue
Date: Mon, 14 Mar 2011 19:03:49 +0100
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Hi all,

on 0.6:=20

we are facing increased write latencies every now and then when an =
unfortunate write command thread becomes the flush writer for a mem =
table because of an already running mem table flush.

I was thinking of setting the work queue in CFS.flushWriterPool to=20

new LinkedBlockingQueue<Runnable>(3) // because 3 is my favorite number

instead of

new =
LinkedBlockingQueue<Runnable>(DatabaseDescriptor.getAllDataFileLocations()=
.length)

while leaving the max threads at 1 (we have only one date dir)

I'm not afraid to OOM. We have enough heap to hold the extra 2 mem =
tables.

Anybody did this and got in trouble?

PS: I know that 0.7 makes this configurable (but also increases writer =
concurrency while I would rather only queue).

Thanks,
Daniel=