From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753869Ab1K2O6c (ORCPT ); Tue, 29 Nov 2011 09:58:32 -0500 Received: from mx1.redhat.com ([209.132.183.28]:24447 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752261Ab1K2O6a (ORCPT ); Tue, 29 Nov 2011 09:58:30 -0500 Message-ID: <4ED4F30F.8000603@redhat.com> Date: Tue, 29 Nov 2011 16:58:23 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:8.0) Gecko/20111115 Thunderbird/8.0 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: Sasha Levin , linux-kernel@vger.kernel.org, Rusty Russell , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, markmc@redhat.com Subject: Re: [PATCH] virtio-ring: Use threshold for switching to indirect descriptors References: <1322559196-11139-1-git-send-email-levinsasha928@gmail.com> <20111129125622.GB19157@redhat.com> <1322573688.4395.11.camel@lappy> <20111129135406.GB30966@redhat.com> <1322576464.7003.6.camel@lappy> <20111129145451.GD30966@redhat.com> In-Reply-To: <20111129145451.GD30966@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/29/2011 04:54 PM, Michael S. Tsirkin wrote: > > > > Which is actually strange, weren't indirect buffers introduced to make > > the performance *better*? From what I see it's pretty much the > > same/worse for virtio-blk. > > I know they were introduced to allow adding very large bufs. > See 9fa29b9df32ba4db055f3977933cd0c1b8fe67cd > Mark, you wrote the patch, could you tell us which workloads > benefit the most from indirect bufs? > Indirects are really for block devices with many spindles, since there the limiting factor is the number of requests in flight. Network interfaces are limited by bandwidth, it's better to increase the ring size and use direct buffers there (so the ring size more or less corresponds to the buffer size). -- error compiling committee.c: too many arguments to function