Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934230Ab3GWUTl (ORCPT ); Tue, 23 Jul 2013 16:19:41 -0400 Received: from webmail.solarflare.com ([12.187.104.25]:63120 "EHLO webmail.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932447Ab3GWUTi (ORCPT ); Tue, 23 Jul 2013 16:19:38 -0400 Message-ID: <1374610772.2072.22.camel@bwh-desktop.uk.level5networks.com> Subject: Re: [PATCHv2 net 2/2] sfc: Reduce RX scatter buffer size, and reduce alignment if appropriate From: Ben Hutchings To: David Miller CC: Geert Uytterhoeven , Heiko Carstens , , "Linux Kernel Development" , , netdev Date: Tue, 23 Jul 2013 21:19:32 +0100 In-Reply-To: <1368482482.3305.50.camel@bwh-desktop.uk.solarflarecom.com> References: <1368482311.3305.48.camel@bwh-desktop.uk.solarflarecom.com> <1368482482.3305.50.camel@bwh-desktop.uk.solarflarecom.com> Organization: Solarflare Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4 (3.6.4-3.fc18) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.17.20.137] X-TM-AS-Product-Ver: SMEX-10.0.0.1412-7.000.1014-20032.005 X-TM-AS-Result: No--12.142000-0.000000-31 X-TM-AS-User-Approved-Sender: Yes X-TM-AS-User-Blocked-Sender: No Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1145 Lines: 27 On Mon, 2013-05-13 at 23:01 +0100, Ben Hutchings wrote: [...] > This still doesn't fix the s390 build because like most architectures > it has NET_IP_ALIGN == 2. When NET_IP_ALIGN != 0 we cannot achieve > cache line alignment at either the start or end of a scatter buffer, > so there is actually no point in padding the buffers to a multiple of > the cache line size. All we need is 4-byte alignment of the network > header, so do that. [...] I was just thinking about this again. Do we need to care about alignment in a page fragment at all? Won't all the headers be pulled into the header area before being accessed with any instructions that would require alignment? (We aren't using build_skb().) Ben. -- Ben Hutchings, Staff Engineer, Solarflare Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/