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 F3FF3C197A0 for ; Thu, 16 Nov 2023 07:02:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229815AbjKPHDB convert rfc822-to-8bit (ORCPT ); Thu, 16 Nov 2023 02:03:01 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48370 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229638AbjKPHDB (ORCPT ); Thu, 16 Nov 2023 02:03:01 -0500 Received: from baidu.com (mx20.baidu.com [111.202.115.85]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 761DE192; Wed, 15 Nov 2023 23:02:55 -0800 (PST) From: "Li,Rongqing" To: "dust.li@linux.alibaba.com" , "netdev@vger.kernel.org" , "linux-s390@vger.kernel.org" Subject: RE: [PATCH][net-next] net/smc: avoid atomic_set and smp_wmb in the tx path when possible Thread-Topic: [PATCH][net-next] net/smc: avoid atomic_set and smp_wmb in the tx path when possible Thread-Index: AQHaGFSsV3lsEoc0T0O8PDgZDtb7pLB8hMpw Date: Thu, 16 Nov 2023 07:02:50 +0000 Message-ID: <64c98eb20e1244b981d0db9a912ce589@baidu.com> References: <20231116022041.51959-1-lirongqing@baidu.com> <20231116061811.GC121324@linux.alibaba.com> In-Reply-To: <20231116061811.GC121324@linux.alibaba.com> Accept-Language: zh-CN, en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.22.206.6] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 X-FEAS-Client-IP: 10.127.64.36 X-FE-Last-Public-Client-IP: 100.100.100.38 X-FE-Policy-ID: 15:10:21:SYSTEM Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org > -----Original Message----- > From: Dust Li > Sent: Thursday, November 16, 2023 2:18 PM > To: Li,Rongqing ; wenjia@linux.ibm.co; > netdev@vger.kernel.org; linux-s390@vger.kernel.org > Subject: Re: [PATCH][net-next] net/smc: avoid atomic_set and smp_wmb in the > tx path when possible > > On Thu, Nov 16, 2023 at 10:20:41AM +0800, Li RongQing wrote: > >there is rare possibility that conn->tx_pushing is not 1, since > >tx_pushing is just checked with 1, so move the setting tx_pushing to 1 > >after atomic_dec_and_test() return false, to avoid atomic_set and > >smp_wmb in tx path > > > >Signed-off-by: Li RongQing > Reviewed-by: Dust Li > > >--- > > net/smc/smc_tx.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > >diff --git a/net/smc/smc_tx.c b/net/smc/smc_tx.c index 3b0ff3b..72dbdee > >100644 > >--- a/net/smc/smc_tx.c > >+++ b/net/smc/smc_tx.c > >@@ -667,8 +667,6 @@ int smc_tx_sndbuf_nonempty(struct smc_connection > *conn) > > return 0; > > > > again: > >- atomic_set(&conn->tx_pushing, 1); > >- smp_wmb(); /* Make sure tx_pushing is 1 before real send */ > > rc = __smc_tx_sndbuf_nonempty(conn); > > > > /* We need to check whether someone else have added some data into > @@ > >-677,8 +675,11 @@ int smc_tx_sndbuf_nonempty(struct smc_connection > *conn) > > * If so, we need to push again to prevent those data hang in the send > > * queue. > > */ > >- if (unlikely(!atomic_dec_and_test(&conn->tx_pushing))) > >+ if (unlikely(!atomic_dec_and_test(&conn->tx_pushing))) { > >+ atomic_set(&conn->tx_pushing, 1); > >+ smp_wmb(); /* Make sure tx_pushing is 1 before real send */ > nit: it would be better if we change the comments to "send again". > Ok, I will fix it, thanks -Li > Thanks > > goto again; > >+ } > > > > return rc; > > } > >-- > >2.9.4