From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A990CC43387 for ; Fri, 4 Jan 2019 21:29:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7647621872 for ; Fri, 4 Jan 2019 21:29:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726266AbfADV3g (ORCPT ); Fri, 4 Jan 2019 16:29:36 -0500 Received: from mx1.redhat.com ([209.132.183.28]:7100 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726021AbfADV3g (ORCPT ); Fri, 4 Jan 2019 16:29:36 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A8D8BCD4CA; Fri, 4 Jan 2019 21:29:35 +0000 (UTC) Received: from redhat.com (ovpn-124-210.rdu2.redhat.com [10.10.124.210]) by smtp.corp.redhat.com (Postfix) with SMTP id BB7A660BE7; Fri, 4 Jan 2019 21:29:34 +0000 (UTC) Date: Fri, 4 Jan 2019 16:29:34 -0500 From: "Michael S. Tsirkin" To: Jason Wang Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net Subject: Re: [RFC PATCH V3 1/5] vhost: generalize adding used elem Message-ID: <20190104162857-mutt-send-email-mst@kernel.org> References: <20181229124656.3900-1-jasowang@redhat.com> <20181229124656.3900-2-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181229124656.3900-2-jasowang@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Fri, 04 Jan 2019 21:29:35 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Dec 29, 2018 at 08:46:52PM +0800, Jason Wang wrote: > Use one generic vhost_copy_to_user() instead of two dedicated > accessor. This will simplify the conversion to fine grain > accessors. About 2% improvement of PPS were seen during vitio-user > txonly test. > > Signed-off-by: Jason Wang I don't hve a problem with this patch but do you have any idea how come removing what's supposed to be an optimization speeds things up? > --- > drivers/vhost/vhost.c | 11 +---------- > 1 file changed, 1 insertion(+), 10 deletions(-) > > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c > index 55e5aa662ad5..f179b5ee14c4 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -2174,16 +2174,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq, > > start = vq->last_used_idx & (vq->num - 1); > used = vq->used->ring + start; > - if (count == 1) { > - if (vhost_put_user(vq, heads[0].id, &used->id)) { > - vq_err(vq, "Failed to write used id"); > - return -EFAULT; > - } > - if (vhost_put_user(vq, heads[0].len, &used->len)) { > - vq_err(vq, "Failed to write used len"); > - return -EFAULT; > - } > - } else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) { > + if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) { > vq_err(vq, "Failed to write used"); > return -EFAULT; > } > -- > 2.17.1