From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: Re: [dm-devel] [PATCH] DM-CRYPT: Scale to multiple CPUs Date: Tue, 01 Jun 2010 08:40:46 +0200 Message-ID: <4C04AB6E.1080305@linux.intel.com> References: <20100531160425.GA20344@basil.fritz.box> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Mikulas Patocka Cc: device-mapper development , herbert@gondor.hengli.com.au, linux-kernel@vger.kernel.org, agk@redhat.com List-Id: dm-devel.ids , 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