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List:       linux-bcache
Subject:    Re: [PATCH] bcache: fix writeback thread to sleep less intrusively
From:       "Darrick J. Wong" <darrick.wong () oracle ! com>
Date:       2014-04-30 17:24:55
Message-ID: 20140430172455.GA3029 () birch ! djwong ! org
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On Wed, Apr 30, 2014 at 01:51:14PM +0200, Daniel Smedegaard Buus wrote:
> Hi :)
> 
> What's the state of this?
> 
> I have this issue on a number of EC2 instances that are using bcache
> to speed up EBS access by caching on the ephemeral SSDs (writethrough
> mode).
> 
> "echo 0 > /sys/block/bcache0/bcache/writeback_running" as suggested by
> others stops the flood of "blocked" messages in dmesg, but it only
> partly fixes the 2.0 minimum load average issue (instead, it's now a
> 1.0 minimum load average).

I haven't spent time on figuring out the other source of load average.  Kent
didn't seem to like the patch to convert the bcache_writeback thread to
interruptible sleep (I recall he said it was 'wrong', but didn't elaborate).

--D
> 
> I just tried the latest kernel I could get my hands on for Ubuntu
> Trusty, the mainline v3.15-rc2 (built April 20th), and it exhibits the
> same behavior.
> 
> Thanks :)
> 
> Daniel
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