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 4A582C43387 for ; Mon, 7 Jan 2019 03:53:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1E04D2070B for ; Mon, 7 Jan 2019 03:53:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726453AbfAGDxt (ORCPT ); Sun, 6 Jan 2019 22:53:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:48628 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726145AbfAGDxs (ORCPT ); Sun, 6 Jan 2019 22:53:48 -0500 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B086780F6D; Mon, 7 Jan 2019 03:53:48 +0000 (UTC) Received: from [10.72.12.172] (ovpn-12-172.pek2.redhat.com [10.72.12.172]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 58732600C1; Mon, 7 Jan 2019 03:53:44 +0000 (UTC) Subject: Re: [RFC PATCH V3 0/5] Hi: To: "Michael S. Tsirkin" Cc: kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, davem@davemloft.net References: <20181229124656.3900-1-jasowang@redhat.com> <20190102154038-mutt-send-email-mst@kernel.org> <0efd115a-a7fb-54bf-5376-59d047a15fd3@redhat.com> <20190106221832-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: Date: Mon, 7 Jan 2019 11:53:41 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190106221832-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 07 Jan 2019 03:53:48 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/1/7 上午11:28, Michael S. Tsirkin wrote: > 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? It's the effect of removing speculation barrier. > >> On machine with SMAP (Broadwell): >> >> Before: 5.0Mpps >> >> After: 6.1Mpps >> >> No smap: 7.5Mpps >> >> >> Thanks > > no smap being before or after? > Let me clarify: Before (SMAP on): 5.0Mpps Before (SMAP off): 7.5Mpps After (SMAP on): 6.1Mpps Thanks