linux-kernel - Re: [PATCH] DM-CRYPT: Scale to multiple CPUs

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Message-ID: <4C040441.9020107@wpkg.org>
Date:	Mon, 31 May 2010 20:47:29 +0200
From:	Tomasz Chmielewski <mangoo@...g.org>
To:	linux-kernel@...r.kernel.org
CC:	mbroz@...hat.com, Andi Kleen <andi@...stfloor.org>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH] DM-CRYPT: Scale to multiple CPUs

Milan Broz wrote:

> On 05/31/2010 06:04 PM, Andi Kleen wrote:
>> DM-CRYPT: Scale to multiple CPUs
>>
>> Currently dm-crypt does all encryption work per dmcrypt mapping in a
>> single workqueue. This does not scale well when multiple CPUs
>> are submitting IO at a high rate. The single CPU running the single
>> thread cannot keep up with the encryption and encrypted IO performance
>> tanks.
>
> This is true only if encryption run on the CPU synchronously.
>
> (Usually it is high speed SSD or dm-crypt above striped RAID where
> underlying device throughput is higher than CPU encryption speed.)

Quite common to hit on a netbook/laptop with encrypted root these days, 
where storage can be relatively fast when compared to the speed of one 
of the cores of the (usually) multicore CPU.


-- 
Tomasz Chmielewski
http://wpkg.org

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