linux-kernel - Re: dm-crypt parallelization patches

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Date:	Tue, 9 Apr 2013 10:57:53 -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

On Tue, Apr 09, 2013 at 01:51:43PM -0400, Mikulas Patocka wrote:
> The patch dm-crypt-sort-requests.patch sorts write requests submitted by a 
> single thread. The requests are sorted according to the sector number, 
> rb-tree is used for efficient sorting.

Hmmm? Why not just keep the issuing order along with plugging
boundaries?

> So it seems that CFQ has some deficiency that it cannot merge adjacent 
> requests done by different processes.

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.

Thanks.

-- 
tejun
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