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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 78015C31E5B for ; Mon, 17 Jun 2019 20:58:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 550942080A for ; Mon, 17 Jun 2019 20:58:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727000AbfFQU6W (ORCPT ); Mon, 17 Jun 2019 16:58:22 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:38196 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726107AbfFQU6W (ORCPT ); Mon, 17 Jun 2019 16:58:22 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::3d5]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id A9B6B15130B18; Mon, 17 Jun 2019 13:58:21 -0700 (PDT) Date: Mon, 17 Jun 2019 13:58:21 -0700 (PDT) Message-Id: <20190617.135821.1970853531857836652.davem@davemloft.net> To: jasowang@redhat.com Cc: mst@redhat.com, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, huhai@kylinos.cn Subject: Re: [PATCH net-next] vhost_net: disable zerocopy by default From: David Miller In-Reply-To: <20190617092054.12299-1-jasowang@redhat.com> References: <20190617092054.12299-1-jasowang@redhat.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Mon, 17 Jun 2019 13:58:21 -0700 (PDT) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Jason Wang Date: Mon, 17 Jun 2019 05:20:54 -0400 > Vhost_net was known to suffer from HOL[1] issues which is not easy to > fix. Several downstream disable the feature by default. What's more, > the datapath was split and datacopy path got the support of batching > and XDP support recently which makes it faster than zerocopy part for > small packets transmission. > > It looks to me that disable zerocopy by default is more > appropriate. It cold be enabled by default again in the future if we > fix the above issues. > > [1] https://patchwork.kernel.org/patch/3787671/ > > Signed-off-by: Jason Wang Applied, thanks Jason.