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 AE38FECAAD8 for ; Tue, 20 Sep 2022 06:23:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229790AbiITGXQ (ORCPT ); Tue, 20 Sep 2022 02:23:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56340 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229580AbiITGXP (ORCPT ); Tue, 20 Sep 2022 02:23:15 -0400 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0A7D55D11C; Mon, 19 Sep 2022 23:23:13 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=guwen@linux.alibaba.com;NM=1;PH=DS;RN=10;SR=0;TI=SMTPD_---0VQHnVja_1663654990; Received: from 30.221.128.170(mailfrom:guwen@linux.alibaba.com fp:SMTPD_---0VQHnVja_1663654990) by smtp.aliyun-inc.com; Tue, 20 Sep 2022 14:23:11 +0800 Message-ID: <1ad45b33-d88a-54b7-fbfa-831f58fca9d2@linux.alibaba.com> Date: Tue, 20 Sep 2022 14:23:09 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH net-next 1/2] net/smc: Introduce a specific sysctl for TEST_LINK time To: dust.li@linux.alibaba.com, kgraul@linux.ibm.com, wenjia@linux.ibm.com, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: linux-s390@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <1663641907-15852-1-git-send-email-guwen@linux.alibaba.com> <1663642434-30035-1-git-send-email-guwen@linux.alibaba.com> <20220920045520.GC108825@linux.alibaba.com> From: Wen Gu In-Reply-To: <20220920045520.GC108825@linux.alibaba.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-s390@vger.kernel.org On 2022/9/20 12:55, dust.li wrote: > On Tue, Sep 20, 2022 at 10:53:54AM +0800, Wen Gu wrote: >> SMC-R tests the viability of link by sending out TEST_LINK LLC >> messages over RoCE fabric when connections on link have been >> idle for a time longer than keepalive interval (testlink time). >> >> But using tcp_keepalive_time as testlink time maybe not quite >> suitable because it is default no less than two hours[1], which >> is too long for single link to find peer dead. The active host >> will still use peer-dead link (QP) sending messages, and can't >> find out until get IB_WC_RETRY_EXC_ERR error CQEs, which takes >> more time than TEST_LINK timeout (SMC_LLC_WAIT_TIME) normally. >> >> So this patch introduces a independent sysctl for SMC-R to set >> link keepalive time, in order to detect link down in time. The >> default value is 30 seconds. >> >> [1] https://www.rfc-editor.org/rfc/rfc1122#page-101 >> >> Signed-off-by: Wen Gu >> --- >> /* called after lgr was removed from lgr_list */ >> diff --git a/net/smc/smc_llc.h b/net/smc/smc_llc.h >> index 4404e52..1de9a29 100644 >> --- a/net/smc/smc_llc.h >> +++ b/net/smc/smc_llc.h >> @@ -19,6 +19,7 @@ >> >> #define SMC_LLC_WAIT_FIRST_TIME (5 * HZ) >> #define SMC_LLC_WAIT_TIME (2 * HZ) >> +#define SMC_LLC_TESTLINK_DEFAULT_TIME 30 > > I'm wondering why we don't follow the upper to macros using (30 * HZ) ? > Thanks for the reivew. Because the value of sysctl_smcr_testlink_time is in seconds, and the value of llc_testlink_time is jiffies. I have thought about 1) using proc_dointvec_jiffies as sysctl's proc_handler just like TCP does. But proc_dointvec_jiffies has no minimum limit, value 0 makes no sense for SMC testlink. 2) using proc_dointvec_ms_jiffies_minmax as proc_handler. But millisecond interval seems expensive for SMC test link. So, I choose to use proc_dointvec_minmax, make sysctl_smcr_testlink_time in seconds, and convert to jiffies when assigning to llc_testlink_time. Thanks, Wen Gu.