From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [RFC]: Support for zero-copy TCP transmit of user space data Date: Fri, 19 Dec 2008 20:38:04 +0300 Message-ID: <494BDBFC.7060707@vlnb.net> References: <494009D7.4020602@vlnb.net> <494012C4.7090304@vlnb.net> <20081210214500.GA24212@ioremap.net> <4941590F.3070705@vlnb.net> <1229022734.3266.67.camel@localhost.localdomain> <4942BAB8.4050007@vlnb.net> <1229110673.3262.94.camel@localhost.localdomain> <49469ADB.6010709@vlnb.net> <20081215231801.GA27168@infradead.org> <4947FA1C.2090509@vlnb.net> <494A97DD.7080503@vlnb.net> <87zlisz9pg.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: linux-mm@kvack.org, Christoph Hellwig , James Bottomley , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, scst-devel@lists.sourceforge.net, Bart Van Assche , netdev@vger.kernel.org To: Andi Kleen Return-path: In-Reply-To: <87zlisz9pg.fsf@basil.nowhere.org> Sender: owner-linux-mm@kvack.org List-Id: netdev.vger.kernel.org Andi Kleen, on 12/19/2008 02:27 PM wrote: > Vladislav Bolkhovitin writes: >> - Although usage of struct page to keep network related pointer might >> look as a layering violation, it isn't. I wrote in >> http://lkml.org/lkml/2008/12/15/190 why. > > Sorry but extending struct page for this is really a bad idea because > of the extreme memory overhead even when it's not used (which is a > problem on distribution kernels) Find some other way to store this > information. Even for patches with more general value it was not > acceptable. Sure, this is why I propose to disable that option by default in distribution kernels, so it would produce no harm. ISCSI-SCST can work in this configuration quite well too. People who need both iSCSI target *and* fast working user space device handlers would simply enable that option and rebuild the kernel. Rejecting this patch provides much worse alternative: those people would also have to *patch* the kernel at first, only then enable that option, then rebuild the kernel. (I'm repeating it to make sure you didn't miss this my point; it was in the part of my original message, which you cut out.) Thanks, Vlad -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org