Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753818Ab3EUObZ (ORCPT ); Tue, 21 May 2013 10:31:25 -0400 Received: from mail-ie0-f173.google.com ([209.85.223.173]:58113 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752878Ab3EUObY (ORCPT ); Tue, 21 May 2013 10:31:24 -0400 MIME-Version: 1.0 In-Reply-To: <519B68A4.3010406@linux.intel.com> References: <20130520101552.14133.45953.stgit@ladj378.jer.intel.com> <519B632F.7040202@mellanox.com> <519B68A4.3010406@linux.intel.com> From: Willem de Bruijn Date: Tue, 21 May 2013 10:30:53 -0400 Message-ID: Subject: Re: [PATCH v3 net-next 0/4] net: low latency Ethernet device polling To: Eliezer Tamir Cc: Alex Rosenbaum , Dave Miller , linux-kernel , netdev@vger.kernel.org, Jesse Brandeburg , Don Skidmore , e1000-devel , Andi Kleen , HPA , Eliezer Tamir Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1056 Lines: 22 >> 2. How is the logic aware of RSS and RFS? >> >> With TCP sockets, the driver knows the specific ring it need to poll so >> this should be mapped and provide the best latency. > > > This code is blissfully oblivious of RFS and RSS, it only assumes that the > packets for a socket are likely to continue to come on the same queue. > The code is designed to be correct even if you get your data on the wrong > queue. (your performance will suffer but no more than that.) > For low latency, you don't want to have to wait for the IPI that RPS sets to redirect packets to another CPU. However, this feature works extremely well with hardware flow steering (nfc/ntuple) and accelerated RFS, where the device will enqueue directly on an rxqueue owned exclusively by the destination cpu (if configured correctly). -- 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/