From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755846Ab1G2Kzt (ORCPT ); Fri, 29 Jul 2011 06:55:49 -0400 Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:47054 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755180Ab1G2Kzs (ORCPT ); Fri, 29 Jul 2011 06:55:48 -0400 Date: Fri, 29 Jul 2011 06:55:40 -0400 From: Christoph Hellwig To: Liu Yuan Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Rusty Russell , Avi Kivity , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Khoa Huynh , Badari Pulavarty Subject: Re: [RFC PATCH]vhost-blk: In-kernel accelerator for virtio block device Message-ID: <20110729105540.GA16250@infradead.org> References: <1311863346-4338-1-git-send-email-namei.unix@gmail.com> <4E326879.9050009@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4E326879.9050009@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 29, 2011 at 03:59:53PM +0800, Liu Yuan wrote: > I noted bdrv_aio_multiwrite() do the murging job, but I am not sure Just like I/O schedulers it's actually fairly harmful on high IOPS, low latency devices. I've just started doing a lot of qemu bencharks, and disabling that multiwrite mess alone gives fairly nice speedups. The major issue seems to be additional memory allocations and cache lines - a problem that actually is fairly inherent all over the qemu code.