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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5919DC4321E for ; Mon, 7 Feb 2022 10:16:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1358379AbiBGKNQ (ORCPT ); Mon, 7 Feb 2022 05:13:16 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44338 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237653AbiBGKDR (ORCPT ); Mon, 7 Feb 2022 05:03:17 -0500 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A17B9C043181; Mon, 7 Feb 2022 02:03:15 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R261e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=tonylu@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0V3p8PEf_1644228192; Received: from localhost(mailfrom:tonylu@linux.alibaba.com fp:SMTPD_---0V3p8PEf_1644228192) by smtp.aliyun-inc.com(127.0.0.1); Mon, 07 Feb 2022 18:03:12 +0800 Date: Mon, 7 Feb 2022 18:03:11 +0800 From: Tony Lu To: Stefan Raspl Cc: kgraul@linux.ibm.com, kuba@kernel.org, davem@davemloft.net, netdev@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH net-next 1/3] net/smc: Send directly when TCP_CORK is cleared Message-ID: Reply-To: Tony Lu References: <20220130180256.28303-1-tonylu@linux.alibaba.com> <20220130180256.28303-2-tonylu@linux.alibaba.com> <74aaa8ce-81a4-b048-cee2-b137279d13d5@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <74aaa8ce-81a4-b048-cee2-b137279d13d5@linux.ibm.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jan 31, 2022 at 08:13:53PM +0100, Stefan Raspl wrote: > On 1/30/22 19:02, Tony Lu wrote: > > According to the man page of TCP_CORK [1], if set, don't send out > > partial frames. All queued partial frames are sent when option is > > cleared again. > > > > When applications call setsockopt to disable TCP_CORK, this call is > > protected by lock_sock(), and tries to mod_delayed_work() to 0, in order > > to send pending data right now. However, the delayed work smc_tx_work is > > also protected by lock_sock(). There introduces lock contention for > > sending data. > > > > To fix it, send pending data directly which acts like TCP, without > > lock_sock() protected in the context of setsockopt (already lock_sock()ed), > > and cancel unnecessary dealyed work, which is protected by lock. > > > > [1] https://linux.die.net/man/7/tcp > > > > Signed-off-by: Tony Lu > > --- > > net/smc/af_smc.c | 4 ++-- > > net/smc/smc_tx.c | 25 +++++++++++++++---------- > > net/smc/smc_tx.h | 1 + > > 3 files changed, 18 insertions(+), 12 deletions(-) > > > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > > index ffab9cee747d..ef021ec6b361 100644 > > --- a/net/smc/af_smc.c > > +++ b/net/smc/af_smc.c > > @@ -2600,8 +2600,8 @@ static int smc_setsockopt(struct socket *sock, int level, int optname, > > sk->sk_state != SMC_CLOSED) { > > if (!val) { > > SMC_STAT_INC(smc, cork_cnt); > > - mod_delayed_work(smc->conn.lgr->tx_wq, > > - &smc->conn.tx_work, 0); > > + smc_tx_pending(&smc->conn); > > + cancel_delayed_work(&smc->conn.tx_work); > > } > > } > > break; > > diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c > > index be241d53020f..7b0b6e24582f 100644 > > --- a/net/smc/smc_tx.c > > +++ b/net/smc/smc_tx.c > > @@ -597,27 +597,32 @@ int smc_tx_sndbuf_nonempty(struct smc_connection *conn) > > return rc; > > } > > -/* Wakeup sndbuf consumers from process context > > - * since there is more data to transmit > > - */ > > -void smc_tx_work(struct work_struct *work) > > +void smc_tx_pending(struct smc_connection *conn) > > Could you add a comment that we're expecting lock_sock() to be held when > calling this function? I will add it in the next separated patch. Thank you, Tony Lu