From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934580Ab0J1VEu (ORCPT ); Thu, 28 Oct 2010 17:04:50 -0400 Received: from e35.co.us.ibm.com ([32.97.110.153]:54422 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752477Ab0J1VEo (ORCPT ); Thu, 28 Oct 2010 17:04:44 -0400 Subject: Re: [RFC PATCH 1/1] vhost: TX used buffer guest signal accumulation From: Sridhar Samudrala To: Shirley Ma Cc: "Michael S. Tsirkin" , David Miller , netdev@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <1288296835.11251.24.camel@localhost.localdomain> References: <1288216693.17571.38.camel@localhost.localdomain> <1288240804.14342.1.camel@localhost.localdomain> <20101028052021.GD5599@redhat.com> <1288294355.11251.20.camel@localhost.localdomain> <1288296835.11251.24.camel@localhost.localdomain> Content-Type: text/plain Date: Thu, 28 Oct 2010 14:04:38 -0700 Message-Id: <1288299878.30131.2.camel@sridhar.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.26.3 (2.26.3-1.fc11) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2010-10-28 at 13:13 -0700, Shirley Ma wrote: > On Thu, 2010-10-28 at 12:32 -0700, Shirley Ma wrote: > > Also I found a big TX regression for old guest and new guest. For old > > guest, I am able to get almost 11Gb/s for 2K message size, but for the > > new guest kernel, I can only get 3.5 Gb/s with the patch and same > > host. > > I will dig it why. > > The regression is from guest kernel, not from this patch. Tested 2.6.31 > kernel, it's performance is less than 2Gb/s for 2K message size already. > I will resubmit the patch for review. > > I will start to test from 2.6.30 kernel to figure it when TX regression > induced in virtio_net. Any suggestion which guest kernel I should test > to figure out this regression? It would be some change in virtio-net driver that may have improved the latency of small messages which in turn would have reduced the bandwidth as TCP could not accumulate and send large packets. Thanks Sridhar