From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ben Hutchings Subject: Re: [RFC PATCH 0/3] Simplified 16 bit Toeplitz hash algorithm Date: Mon, 03 Jan 2011 19:30:39 +0000 Message-ID: <1294083039.3167.184.camel@localhost> References: <20101218004210.28602.18499.stgit@gitlad.jf.intel.com> <20110103.110244.183045594.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: therbert@google.com, alexander.h.duyck@intel.com, netdev@vger.kernel.org To: David Miller Return-path: Received: from exchange.solarflare.com ([216.237.3.220]:12967 "EHLO exchange.solarflare.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751783Ab1ACTaq (ORCPT ); Mon, 3 Jan 2011 14:30:46 -0500 In-Reply-To: <20110103.110244.183045594.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, 2011-01-03 at 11:02 -0800, David Miller wrote: > From: Tom Herbert > Date: Mon, 3 Jan 2011 10:47:20 -0800 > > > I'm not sure why this would be needed. What is the a advantage in > > making the TX and RX queues match? > > That's how their hardware based RFS essentially works. > > Instead of watching for "I/O system calls" like we do in software, the > chip watches for which TX queue a flow ends up on and matches things > up on the receive side with the same numbered RX queue to match. ixgbe also implements IRQ affinity setting (or rather hinting) and TX queue selection by CPU, the inverse of IRQ affinity setting. Together with the hardware/firmware Flow Director feature, this should indeed result in hardware RFS. (However, irqbalanced does not yet follow the affinity hints AFAIK, so this requires some manual intervention. Maybe the OOT driver is different?) The proposed change to make TX queue selection hash-based seems to be a step backwards. 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.