From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751899Ab3HTCgX (ORCPT ); Mon, 19 Aug 2013 22:36:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59238 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751401Ab3HTCgW (ORCPT ); Mon, 19 Aug 2013 22:36:22 -0400 Message-ID: <5212D61B.1010303@redhat.com> Date: Tue, 20 Aug 2013 10:36:11 +0800 From: Jason Wang User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130803 Thunderbird/17.0.8 MIME-Version: 1.0 To: "Michael S. Tsirkin" CC: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/6] vhost: switch to use vhost_add_used_n() References: <1376630190-5912-1-git-send-email-jasowang@redhat.com> <1376630190-5912-4-git-send-email-jasowang@redhat.com> <20130816095655.GB21821@redhat.com> In-Reply-To: <20130816095655.GB21821@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 08/16/2013 05:56 PM, Michael S. Tsirkin wrote: > On Fri, Aug 16, 2013 at 01:16:27PM +0800, Jason Wang wrote: >> > Let vhost_add_used() to use vhost_add_used_n() to reduce the code duplication. >> > >> > Signed-off-by: Jason Wang > Does compiler inline it then? > Reason I ask, last time I checked put_user inside vhost_add_used > was much cheaper than copy_to_user inside vhost_add_used_n, > so I wouldn't be surprised if this hurt performance. > Did you check? > I run virtio_test but didn't see the difference. Did you mean the might_fault() in __copy_to_user()? So how about switch to use __put_user() if count is one in __vhost_add_used_n()?