linux-kernel - Re: dm-crypt parallelization patches

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Date:	Tue, 9 Apr 2013 11:10:31 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Mikulas Patocka <mpatocka@...hat.com>
Cc:	Jens Axboe <axboe@...nel.dk>, Vivek Goyal <vgoyal@...hat.com>,
	Mike Snitzer <snitzer@...hat.com>,
	Milan Broz <gmazyland@...il.com>, dm-devel@...hat.com,
	Andi Kleen <andi@...stfloor.org>, dm-crypt@...ut.de,
	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Christian Schmidt <schmidt@...add.de>
Subject: Re: dm-crypt parallelization patches

Hey,

On Tue, Apr 09, 2013 at 02:08:06PM -0400, Mikulas Patocka wrote:
> > Hmmm? Why not just keep the issuing order along with plugging
> > boundaries?
> 
> What do you mean?
> 
> I used to have a patch that keeps order of requests as they were 
> introduced, but sorting the requests according to sector number is a bit 
> simpler.

You're still destroying the context information.  Please just keep the
issuing order along with plugging boundaries.

> > As I wrote before, please use bio_associate_current().  Currently,
> > dm-crypt is completely messing up all the context information that cfq
> > depends on to schedule IOs.  Of course, it doesn't perform well.
> 
> bio_associate_current() is only valid on a system with cgroups and there 
> are no cgroups on the kernel where I tested it. It is an empty function:
> 
> static inline int bio_associate_current(struct bio *bio) { return -ENOENT; }

Yeah, because blkcg was the only user.  Please feel free to drop the
ifdefs.  It covers both iocontext and cgroup association.

Thanks.

-- 
tejun
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