From: Ted Ts'o <tytso@mit.edu>
Subject: Re: [PATCH, RFC] Don't do page stablization if
 !CONFIG_BLKDEV_INTEGRITY
Date: Fri, 9 Mar 2012 11:20:05 -0500
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To: Chris Mason <chris.mason@oracle.com>,
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On Thu, Mar 08, 2012 at 08:02:07PM -0500, Chris Mason wrote:
> > Right before submission to the bio layer?  Or right before the device
> > driver sends the request to the host bus adapter?  I was thinking of
> > the latter....
> 
> blktrace can probably give us numbers for how big that wait is, but
> hopefully it is very small.  If it is too big, you can always bump
> nr_requests.

Not necessarily; things can get stalled for quite a while due to
ionice or io rate throttling.  There's quite a lot that can happen
after submit_bio, at the cfq layer, for example.

						- Ted