From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pekka Enberg Subject: Re: [PATCH 1/2] kvm tools: Respect ISR status in virtio header Date: Sat, 07 May 2011 17:52:40 +0300 Message-ID: <1304779960.10621.16.camel@jaguar> References: <1304735660-10844-1-git-send-email-asias.hejun@gmail.com> <20110507093027.GD27657@elte.hu> <4DC545BA.3030501@us.ibm.com> <20110507140251.GB2859@elte.hu> <4DC55562.4070304@codemonkey.ws> <20110507144735.GD2859@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: Anthony Liguori , Asias He , "Michael S. Tsirkin" , Rusty Russell , Mark McLoughlin , Cyrill Gorcunov , Sasha Levin , Prasad Joshi , kvm@vger.kernel.org To: Ingo Molnar Return-path: Received: from filtteri6.pp.htv.fi ([213.243.153.189]:45918 "EHLO filtteri6.pp.htv.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755289Ab1EGOwm (ORCPT ); Sat, 7 May 2011 10:52:42 -0400 In-Reply-To: <20110507144735.GD2859@elte.hu> Sender: kvm-owner@vger.kernel.org List-ID: On Sat, 2011-05-07 at 16:47 +0200, Ingo Molnar wrote: > Can you anything in the virtio protocol implementation that would explain > networking lags, which seem to be caused by guest notifications either not be > sent or being missed? > > In particular this sequence: > > > while pending_requests: > > a = get_next_request(); > > process_next_request(a); > > is apparently not what Qemu uses - so maybe there's some latent bug or some > silly oversight somewhere. > > It is suboptimal and i agree with you that the better sequence should be > implemented, but the above *should* work, yet it does not. Yes, so the performance benefits of Asias' patch aren't the interesting part but the fact that it fixes a real bug in our tool. Pekka