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Message-ID: <4C04AB6E.1080305@linux.intel.com>
Date: Tue, 01 Jun 2010 08:40:46 +0200
From: Andi Kleen <ak@...ux.intel.com>
To: Mikulas Patocka <mpatocka@...hat.com>
CC: device-mapper development <dm-devel@...hat.com>,
herbert@...dor.hengli.com.au, linux-kernel@...r.kernel.org,
agk@...hat.com
Subject: Re: [dm-devel] [PATCH] DM-CRYPT: Scale to multiple CPUs
, Mikulas Patocka wrote:
> Questions:
>
> If you are optimizing it,
>
> 1) why don't you optimize it in such a way that if one CPU submits
> requests, the crypto work is spread among all the CPUs? Currently it
> spreads the work only if different CPUs submit it.
This case is only useful with very slow CPUs and is handled by pcrypt
in theory
(but I haven't tested it)
>
> 2) why not optimize software async crypto daemon (crypt/cryptd.c) instead
> of dm-crypt, so that all kernel subsystems can actually take advantage of
> those multi-CPU optimizations, not just dm-crypt?
Normally most subsystems are multi-CPU already, unless they limit
themselves artitifically like dm-crypt.
For dm-crypt would be wasteful to funnel everything through two single CPU threads just
to spread it out again. That is why I also used per CPU IO threads too.
-Andi
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