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=unavailable 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 14CC7C282C0 for ; Fri, 25 Jan 2019 09:16:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E2ED0218D0 for ; Fri, 25 Jan 2019 09:16:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729072AbfAYJQv (ORCPT ); Fri, 25 Jan 2019 04:16:51 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41894 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726269AbfAYJQv (ORCPT ); Fri, 25 Jan 2019 04:16:51 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 31A30CF311; Fri, 25 Jan 2019 09:16:51 +0000 (UTC) Received: from [10.72.12.101] (ovpn-12-101.pek2.redhat.com [10.72.12.101]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8FAC36153A; Fri, 25 Jan 2019 09:16:35 +0000 (UTC) Subject: Re: [PATCH net-next V4 5/5] vhost: access vq metadata through kernel virtual address To: "Michael S. Tsirkin" Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org References: <20190123095557.30168-1-jasowang@redhat.com> <20190123095557.30168-6-jasowang@redhat.com> <20190123085821-mutt-send-email-mst@kernel.org> <335ba55b-087f-4b35-6311-540070b9647f@redhat.com> <20190124215912-mutt-send-email-mst@kernel.org> From: Jason Wang Message-ID: <18e64692-2598-6e95-3b93-c34528d04c1b@redhat.com> Date: Fri, 25 Jan 2019 17:16:32 +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: <20190124215912-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 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Fri, 25 Jan 2019 09:16:51 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2019/1/25 上午11:00, Michael S. Tsirkin wrote: > On Thu, Jan 24, 2019 at 12:07:54PM +0800, Jason Wang wrote: >>> Meanwhile, could you pls post data comparing this last patch with the >>> below? This removes the speculation barrier replacing it with a >>> (useless but at least more lightweight) data dependency. >> SMAP off >> >> Your patch: 7.2MPPs >> >> vmap: 7.4Mpps > OK so while we keep looking into vmap, why don't we merge something like > the below? Seems quite straight forward ... > The problem is it gives ~8% regression on PPS when SMAP is on. This is probably because the latency of lfence is hided by previous stac as mentioned in the commit b3bbfb3fb5d25776b8e3f361d2eedaabb0b496cd. Thanks