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 11:45:47 -0800 Message-ID: <1296157547.1640.45.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> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Steve Dobbelstein , kvm@vger.kernel.org To: "Michael S. Tsirkin" Return-path: Received: from e3.ny.us.ibm.com ([32.97.182.143]:58237 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751648Ab1A0Tqh (ORCPT ); Thu, 27 Jan 2011 14:46:37 -0500 Received: from d01dlp01.pok.ibm.com (d01dlp01.pok.ibm.com [9.56.224.56]) by e3.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p0RJOhCq014856 for ; Thu, 27 Jan 2011 14:27:23 -0500 Received: from d01relay03.pok.ibm.com (d01relay03.pok.ibm.com [9.56.227.235]) by d01dlp01.pok.ibm.com (Postfix) with ESMTP id 63B1072816A for ; Thu, 27 Jan 2011 14:45:50 -0500 (EST) Received: from d01av02.pok.ibm.com (d01av02.pok.ibm.com [9.56.224.216]) by d01relay03.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p0RJjoen266860 for ; Thu, 27 Jan 2011 14:45:50 -0500 Received: from d01av02.pok.ibm.com (loopback [127.0.0.1]) by d01av02.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p0RJjnAL015504 for ; Thu, 27 Jan 2011 17:45:49 -0200 In-Reply-To: <20110127193131.GD5228@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On Thu, 2011-01-27 at 21:31 +0200, Michael S. Tsirkin wrote: > Well slowing down the guest does not sound hard - for example we can > request guest notifications, or send extra interrupts :) > A slightly more sophisticated thing to try is to > poll the vq a bit more aggressively. > For example if we handled some requests and now tx vq is empty, > reschedule and yeild. Worth a try? I used dropping packets in high level to slow down TX. I am still thinking what's the right the approach here. 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. By polling the vq a bit more aggressively, you meant vhost, right? Shirley