From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: Network performance with small packets Date: Thu, 3 Feb 2011 18:20:42 +0200 Message-ID: <20110203162042.GA10028@redhat.com> References: <20110202173213.GA13907@redhat.com> <1296670311.25430.49.camel@localhost.localdomain> <20110202182720.GB14257@redhat.com> <1296674975.25430.59.camel@localhost.localdomain> <20110202201731.GB15150@redhat.com> <1296680585.25430.98.camel@localhost.localdomain> <20110202212047.GD15150@redhat.com> <1296709556.25430.140.camel@localhost.localdomain> <20110203061326.GC22230@redhat.com> <1296748680.25430.169.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Krishna Kumar2 , David Miller , kvm@vger.kernel.org, mashirle@linux.vnet.ibm.com, netdev@vger.kernel.org, netdev-owner@vger.kernel.org, Sridhar Samudrala , Steve Dobbelstein To: Shirley Ma Return-path: Received: from mx1.redhat.com ([209.132.183.28]:57441 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752448Ab1BCQVG (ORCPT ); Thu, 3 Feb 2011 11:21:06 -0500 Content-Disposition: inline In-Reply-To: <1296748680.25430.169.camel@localhost.localdomain> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, Feb 03, 2011 at 07:58:00AM -0800, Shirley Ma wrote: > On Thu, 2011-02-03 at 08:13 +0200, Michael S. Tsirkin wrote: > > > Initial TCP_STREAM performance results I got for guest to local > > host > > > 4.2Gb/s for 1K message size, (vs. 2.5Gb/s) > > > 6.2Gb/s for 2K message size, and (vs. 3.8Gb/s) > > > 9.8Gb/s for 4K message size. (vs.5.xGb/s) > > > > What is the average packet size, # bytes per ack, and the # of > > interrupts > > per packet? It could be that just slowing down trahsmission > > makes GSO work better. > > There is no TX interrupts with dropping packet. > > GSO/TSO is the key for small message performance, w/o GSO/TSO, the > performance is limited to about 2Gb/s no matter how big the message size > it is. I think any work we try here will increase large packet size > rate. BTW for dropping packet, TCP increased fast retrans, not slow > start. > > I will collect tcpdump, netstart before and after data to compare packet > size/rate w/o w/i the patch. > > Thanks > Shirley Just a thought: does it help to make tx queue len of the virtio device smaller? E.g. match the vq size? -- MST