linux-kernel - Re: [PATCH 2/2] cfq-iosched: Take care of corner cases of group losing share due to deletion

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Date:	Wed, 9 Dec 2009 15:39:41 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Jens Axboe <jens.axboe@...cle.com>, linux-kernel@...r.kernel.org,
	guijianfeng@...fujitsu.com
Subject: Re: [PATCH 2/2] cfq-iosched: Take care of corner cases of group
	losing share due to deletion

On Wed, Dec 09, 2009 at 02:06:10PM -0500, Jeff Moyer wrote:
> Vivek Goyal <vgoyal@...hat.com> writes:
> 
> > Reported-by: Gui Jianfeng <guijianfeng@...fujitsu.com> 
> > Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
> 
> > +	/*
> > +	 * If think times is less than a jiffy than ttime_mean=0 and above
> > +	 * will not be true. It might happen that slice has not expired yet
> > +	 * but will expire soon (4-5 ns) during select_queue(). To cover the
> 
> 4-5ns?  I'm not sure why you chose these numbers.  Is that what you saw
> in testing?

Yes, that was the number I observed in blktrace while I was debugging
the issue.

>  Anyway, I'm ok with the change, I dislike the reference to
> time when a single jiffy could be up to 10ms.
> 
> Reviewed-by: Jeff Moyer <jmoyer@...hat.com>
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