From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [RFC v2: Patch 1/3] net: hand off skb list to other cpu to submit to upper layer Date: Fri, 13 Mar 2009 11:51:37 -0700 (PDT) Message-ID: <20090313.115137.254924980.davem@davemloft.net> References: <1236866906.3221.11.camel@achroite> <1236926602.2567.528.camel@ymzhang> <65634d660903131006n44f068dw18b2fe9dce25399e@mail.gmail.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: yanmin_zhang@linux.intel.com, bhutchings@solarflare.com, andi@firstfloor.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, herbert@gondor.apana.org.au, jesse.brandeburg@intel.com, shemminger@vyatta.com To: therbert@google.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:48250 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751636AbZCMSvv (ORCPT ); Fri, 13 Mar 2009 14:51:51 -0400 In-Reply-To: <65634d660903131006n44f068dw18b2fe9dce25399e@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Tom Herbert Date: Fri, 13 Mar 2009 10:06:56 -0700 > You'll definitely want to look at the hardware provided hash. We've > been using a 10G NIC which provides a Toeplitz hash (the one defined > by Microsoft) and a software RSS-like capability to move packets from > an interrupting CPU to another for processing. The hash could be used > to index to a set of CPUs, but we also use the hash as a connection > identifier to key into a lookup table to steer packets to the CPU > where the application is running based on the running CPU of the last > recvmsg. Using the device provided hash in this manner is a HUGE win, > as opposed to taking cache misses to get 4-tuple from packet itself to > compute a hash. I posted some patches a while back on our work if > you're interested. I never understood this. If you don't let the APIC move the interrupt around, the individual MSI-X interrupts will steer packets to individual specific CPUS and as a result the scheduler will migrate tasks over to those cpus since the wakeup events keep occuring there.