From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: suggested vhost link speed settings Date: Sun, 28 Nov 2010 16:03:52 +0300 Message-ID: <4CF25338.6030206@msgid.tls.msk.ru> References: <1290911168.20434.1407472791@webmail.messagingengine.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: KVM mailing list To: linux_kvm@proinbox.com Return-path: Received: from isrv.corpit.ru ([86.62.121.231]:58531 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752437Ab0K1NDy (ORCPT ); Sun, 28 Nov 2010 08:03:54 -0500 In-Reply-To: <1290911168.20434.1407472791@webmail.messagingengine.com> Sender: kvm-owner@vger.kernel.org List-ID: 28.11.2010 05:26, linux_kvm@proinbox.com wrote: > Hi list, > > Being that the virtio interfaces are stated as acheiving 5-8 Gb > throughput now with vhost, as opposed to 1Gb without, how should their > link speed be defined when the choices are 2500M or 10000M? The reported link speed for _any_ virtual NIC has no meaning at all, except of the numbers somewhere in ifconfig or equivalent. The actual speed is always limited by the host CPU and the effectiveness of the implementation currently in use. So, it is merely a cosmetic thing, nothing more. The only possible usage for this number (reported link speed) is to let some visualisation tools to draw their graphs, to show "link utilisation" percentage for example. But for that, there's no actual utilisation either - it depends on the current host CPU speed, - f.e. you put additional load to the CPU and the max speed will be lower, but your visualisator will report low utilization. In short: don't try to visualize "link utilization", it has no meaning. As of actual speeds, I can reach ~2Gbps on my somewhat-old-now 2.4GHz Phenom 9750 (first gen) even without vhost-net. /mjt