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=no 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 332DAC433FF for ; Fri, 9 Aug 2019 18:07:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1672D20B7C for ; Fri, 9 Aug 2019 18:07:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2437363AbfHISHI (ORCPT ); Fri, 9 Aug 2019 14:07:08 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:35854 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726582AbfHISHI (ORCPT ); Fri, 9 Aug 2019 14:07:08 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (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 15A7C15422F8B; Fri, 9 Aug 2019 11:07:08 -0700 (PDT) Date: Fri, 09 Aug 2019 11:07:05 -0700 (PDT) Message-Id: <20190809.110705.591778512450074017.davem@davemloft.net> To: edumazet@google.com Cc: netdev@vger.kernel.org, eric.dumazet@gmail.com, soheil@google.com Subject: Re: [PATCH net-next] tcp: batch calls to sk_flush_backlog() From: David Miller In-Reply-To: <20190809120447.93591-1-edumazet@google.com> References: <20190809120447.93591-1-edumazet@google.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]); Fri, 09 Aug 2019 11:07:08 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Date: Fri, 9 Aug 2019 05:04:47 -0700 > Starting from commit d41a69f1d390 ("tcp: make tcp_sendmsg() aware of socket backlog") > loopback flows got hurt, because for each skb sent, the socket receives an > immediate ACK and sk_flush_backlog() causes extra work. > > Intent was to not let the backlog grow too much, but we went a bit too far. > > We can check the backlog every 16 skbs (about 1MB chunks) > to increase TCP over loopback performance by about 15 % > > Note that the call to sk_flush_backlog() handles a single ACK, > thanks to coalescing done on backlog, but cleans the 16 skbs > found in rtx rb-tree. > > Reported-by: Soheil Hassas Yeganeh > Signed-off-by: Eric Dumazet Applied.