From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wright Subject: Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33 Date: Wed, 23 Dec 2009 10:31:29 -0800 Message-ID: <20091223183129.GB415@sequoia.sous-sol.org> References: <4B1D4F29.8020309@gmail.com> <4B30F214.80206@codemonkey.ws> <20091223065129.GA19600@elte.hu> <200912231407.20130.bzolnier@gmail.com> <4B322FE1.2070104@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Bartlomiej Zolnierkiewicz , Ingo Molnar , Andi Kleen , Gregory Haskins , Avi Kivity , kvm@vger.kernel.org, Andrew Morton , torvalds@linux-foundation.org, "linux-kernel@vger.kernel.org" , netdev@vger.kernel.org, "alacrityvm-devel@lists.sourceforge.net" To: Anthony Liguori Return-path: Received: from sous-sol.org ([216.99.217.87]:59581 "EHLO sequoia.sous-sol.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751880AbZLWSev (ORCPT ); Wed, 23 Dec 2009 13:34:51 -0500 Content-Disposition: inline In-Reply-To: <4B322FE1.2070104@codemonkey.ws> Sender: netdev-owner@vger.kernel.org List-ID: * Anthony Liguori (anthony@codemonkey.ws) wrote: > The "poor" packet latency of virtio-net is a result of the fact that we > do software timer based TX mitigation. We do this such that we can > decrease the number of exits per-packet and increase throughput. We set > a timer for 250ms and per-packet latency will be at least that much. Actually that's 150us ;-) It's the AlacrityVM numbers that show 250us (note micro, not milli) for latency. That makes sense, shave off 150us for the timer and you're left w/ 100us, which is not substantially slower than what we see (for that bare metal latency we see ~60us) when we switched tx mitigation schemes from timer based to thread scheduling. Quite similar to the 56.8us that vbus/venet shows. thanks, -chris