linux-kernel - Re: [patch 0/4] [RFC] Another proportional weight IO controller

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Message-Id: <20081120.182053.220301508585579959.ryov@valinux.co.jp>
Date:	Thu, 20 Nov 2008 18:20:53 +0900 (JST)
From:	Ryo Tsuruta <ryov@...inux.co.jp>
To:	vgoyal@...hat.com
Cc:	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org,
	virtualization@...ts.linux-foundation.org, jens.axboe@...cle.com,
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	riel@...hat.com, jmoyer@...hat.com, peterz@...radead.org,
	fchecconi@...il.com, paolo.valente@...more.it
Subject: Re: [patch 0/4] [RFC] Another proportional weight IO controller

Hi Vivek,

Sorry for late reply.

> > > Do you have any benchmark results?
> > > I'm especially interested in the followings:
> > > - Comparison of disk performance with and without the I/O controller patch.
> > 
> > If I dynamically disable the bio control, then I did not observe any
> > impact on performance. Because in that case practically it boils down
> > to just an additional variable check in __make_request().
> > 
> 
> Oh.., I understood your question wrong. You are looking for what's the 
> performance penalty if I enable the IO controller on a device.

Yes, that is what I want to know.

> I have not done any extensive benchmarking. If I run two dd commands
> without controller, I get 80MB/s from disk (roughly 40 MB for each task).
> With bio group enabled (default token=2000), I was getting total BW of
> roughly 68 MB/s.
>
> I have not done any performance analysis or optimizations at this point of
> time. I plan to do that once we have some sort of common understanding about
> a particular approach. There are so many IO controllers floating, right now
> I am more concerned if we can all come to a common platform.

I understood the reason of posting the patch well.

> Ryo, do you still want to stick to two level scheduling? Given the problem
> of it breaking down underlying scheduler's assumptions, probably it makes
> more sense to the IO control at each individual IO scheduler.

I don't want to stick to it. I'm considering implementing dm-ioband's
algorithm into the block I/O layer experimentally.

Thanks,
Ryo Tsuruta
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