From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: ip_summed setting for TCP pure-ACK packets Date: Mon, 08 Nov 2010 16:35:13 +0000 Message-ID: <1289234113.2222.20.camel@achroite.uk.solarflarecom.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: sf-linux-drivers , netdev To: David Miller Return-path: Received: from mail.solarflare.com ([216.237.3.220]:52718 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751904Ab0KHQfR (ORCPT ); Mon, 8 Nov 2010 11:35:17 -0500 Sender: netdev-owner@vger.kernel.org List-ID: As we discussed at LPC: Current controllers handled by the sfc driver have a per-queue (rather than per-packet) option for checksum generation. Currently pure-ACK packets sent by TCP have ip_summed == CHECKSUM_NONE and we must send them on hardware queues with checksum generation disabled. To support this, we allocate 2 hardware queues per core TX queue. To reduce the risk of reordering (and possibly the number of hardware TX queues required), it would be helpful for TCP to set ip_summed == CHECKSUM_PARTIAL on pure-ACK packets when the output device is known to support checksum generation. Ben. -- Ben Hutchings, Senior Software Engineer, Solarflare Communications Not speaking for my employer; that's the marketing department's job. They asked us to note that Solarflare product names are trademarked.