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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 3568DC43387 for ; Mon, 7 Jan 2019 03:29:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0D86921738 for ; Mon, 7 Jan 2019 03:29:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726500AbfAGD27 (ORCPT ); Sun, 6 Jan 2019 22:28:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:39426 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726241AbfAGD26 (ORCPT ); Sun, 6 Jan 2019 22:28:58 -0500 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7081887628; Mon, 7 Jan 2019 03:28:58 +0000 (UTC) Received: from redhat.com (ovpn-120-33.rdu2.redhat.com [10.10.120.33]) by smtp.corp.redhat.com (Postfix) with ESMTP id 738321057049; Mon, 7 Jan 2019 03:28:57 +0000 (UTC) Date: Sun, 6 Jan 2019 22:28:56 -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 0/5] Hi: Message-ID: <20190106221832-mutt-send-email-mst@kernel.org> References: <20181229124656.3900-1-jasowang@redhat.com> <20190102154038-mutt-send-email-mst@kernel.org> <0efd115a-a7fb-54bf-5376-59d047a15fd3@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <0efd115a-a7fb-54bf-5376-59d047a15fd3@redhat.com> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Mon, 07 Jan 2019 03:28:58 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 07, 2019 at 10:19:03AM +0800, Jason Wang wrote: > > On 2019/1/3 上午4:47, Michael S. Tsirkin wrote: > > On Sat, Dec 29, 2018 at 08:46:51PM +0800, Jason Wang wrote: > > > This series tries to access virtqueue metadata through kernel virtual > > > address instead of copy_user() friends since they had too much > > > overheads like checks, spec barriers or even hardware feature > > > toggling. > > Will review, thanks! > > One questions that comes to mind is whether it's all about bypassing > > stac/clac. Could you please include a performance comparison with > > nosmap? > > > > On machine without SMAP (Sandy Bridge): > > Before: 4.8Mpps > > After: 5.2Mpps OK so would you say it's really unsafe versus safe accesses? Or would you say it's just a better written code? > On machine with SMAP (Broadwell): > > Before: 5.0Mpps > > After: 6.1Mpps > > No smap: 7.5Mpps > > > Thanks no smap being before or after? -- MST