From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shirley Ma Subject: Re: Network performance with small packets Date: Thu, 27 Jan 2011 12:15:05 -0800 Message-ID: <1296159305.1640.50.camel@localhost.localdomain> References: <20110126151700.GA14113@redhat.com> <1296153874.1640.27.camel@localhost.localdomain> <20110127190031.GC5228@redhat.com> <1296155340.1640.34.camel@localhost.localdomain> <20110127193131.GD5228@redhat.com> <1296157547.1640.45.camel@localhost.localdomain> <20110127200548.GE5228@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Steve Dobbelstein , kvm@vger.kernel.org, netdev@vger.kernel.org To: "Michael S. Tsirkin" Return-path: Received: from e8.ny.us.ibm.com ([32.97.182.138]:45457 "EHLO e8.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752516Ab1A0UPd (ORCPT ); Thu, 27 Jan 2011 15:15:33 -0500 In-Reply-To: <20110127200548.GE5228@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2011-01-27 at 22:05 +0200, Michael S. Tsirkin wrote: > Interesting. Could this is be a variant of the now famuous bufferbloat > then? > > I guess we could drop some packets if we see we are not keeping up. > For > example if we see that the ring is > X% full, we could quickly > complete > Y% without transmitting packets on. Or maybe we should drop some bytes > not packets. It's worth to try to figure out what's the best approach. I will make a patch. > > > > Requesting guest notification and extra interrupts is what we want > to > > avoid to reduce VM exits for saving CPUs. I don't think it's good. > > Yes but how do you explain regression? > One simple theory is that guest net stack became faster > and so the host can't keep up. Yes, that's what I think here. Some qdisc code has been changed recently. > > > > By polling the vq a bit more aggressively, you meant vhost, right? > > > > Shirley > > Yes. I had a similar patch before, I can modify it and test it out. Shirley