From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753428AbdIEVsH (ORCPT ); Tue, 5 Sep 2017 17:48:07 -0400 Received: from shards.monkeyblade.net ([184.105.139.130]:39852 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753151AbdIEVsF (ORCPT ); Tue, 5 Sep 2017 17:48:05 -0400 Date: Tue, 05 Sep 2017 14:48:04 -0700 (PDT) Message-Id: <20170905.144804.755338183074090970.davem@davemloft.net> To: jasowang@redhat.com Cc: mst@redhat.com, netdev@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net V2] vhost_net: correctly check tx avail during rx busy polling From: David Miller In-Reply-To: <1504574525-4711-1-git-send-email-jasowang@redhat.com> References: <1504574525-4711-1-git-send-email-jasowang@redhat.com> X-Mailer: Mew version 6.7 on Emacs 25.2 / Mule 6.0 (HANACHIRUSATO) 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]); Tue, 05 Sep 2017 14:48:04 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jason Wang Date: Tue, 5 Sep 2017 09:22:05 +0800 > We check tx avail through vhost_enable_notify() in the past which is > wrong since it only checks whether or not guest has filled more > available buffer since last avail idx synchronization which was just > done by vhost_vq_avail_empty() before. What we really want is checking > pending buffers in the avail ring. Fix this by calling > vhost_vq_avail_empty() instead. > > This issue could be noticed by doing netperf TCP_RR benchmark as > client from guest (but not host). With this fix, TCP_RR from guest to > localhost restores from 1375.91 trans per sec to 55235.28 trans per > sec on my laptop (Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz). > > Fixes: 030881372460 ("vhost_net: basic polling support") > Signed-off-by: Jason Wang Applied and queued up for -stable, thanks.