From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: Disabling XPS for 4.4.0-1+ixgbe+OpenStack VM over a VLAN means 65% increase in netperf TCP_STREAM Date: Thu, 4 Feb 2016 12:28:09 -0800 Message-ID: <56B3B459.5040204@hpe.com> References: <56B3A2D4.1010309@hpe.com> <56B3AD3F.9070404@hpe.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Linux Kernel Network Developers To: Tom Herbert Return-path: Received: from g9t5009.houston.hp.com ([15.240.92.67]:43929 "EHLO g9t5009.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932861AbcBDU2L (ORCPT ); Thu, 4 Feb 2016 15:28:11 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On 02/04/2016 12:13 PM, Tom Herbert wrote: > On Thu, Feb 4, 2016 at 11:57 AM, Rick Jones wrote: >> On 02/04/2016 11:38 AM, Tom Herbert wrote: >>> XPS has OOO avoidance for TCP, that should not be a problem. >> >> >> What/how much should I read into: >> >> With XPS TCPOFOQueue: 78206 >> Without XPS TCPOFOQueue: 967 >> >> out of the netstat statistics on the receiving VM? >> > Okay, that makes sense. The OOO avoidance only applies to TCP sockets > in the stack, that doesn't cross into VM. Presumably, packets coming > from the VM don't have a socket so sk_tx_queue_get always returns -1 > and so netdev_pick_tx will steer packet to the queue based on > currently running CPU without any memory. Any thoughts as to why explicitly binding the IRQs made things better, or for that matter why the scheduler would be moving the VM (or its vhost-net kernel thread I suppose?) around so much? happy benchmarking, rick jones