Subject: Re: [PATCHv4 12/14] writeback: optimize periodic bdi thread wakeups
From: Artem Bityutskiy <dedekind1@gmail.com>
Reply-To: dedekind1@gmail.com
To: Christoph Hellwig <hch@infradead.org>
Cc: Jens Axboe <axboe@kernel.dk>, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <20100723162800.GB29633@infradead.org>
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Date: Sat, 24 Jul 2010 09:00:08 +0300
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On Fri, 2010-07-23 at 12:28 -0400, Christoph Hellwig wrote:
> I haven't reviewed this in detail, but what ensures the timer is
> synchronously removed when the forker goes away?

Good point, thanks.

>   I don't see a
> del_timer_sync call anywhere.  For now it might be easier to just
> skip this patch and leave it for later.

Well, my tests showed that with this patch the flushers wake up
considerably less. So I'll try to come up with a better patch.

I will set-up better testing. Will hack things so that the background
dirty writeout timeout is something like 1-3 jiffies and the bdi thread
inactive timeout is something like 3-5 jiffies. Then will write a script
which forks many tasks each of each creates a loop-back device, mounts
it, does some I/O, unmounts, removes the loop-back device, and so on. If
run for long time, it should give good stress to the code paths I'm
working on. I have a 2-way 4-core (total 8) amd64 testbox to test.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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