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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED autolearn=ham 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 D3C83C1B0F1 for ; Wed, 20 Jun 2018 01:27:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7AE8720693 for ; Wed, 20 Jun 2018 01:27:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="eFlOgAyW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7AE8720693 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754061AbeFTB15 (ORCPT ); Tue, 19 Jun 2018 21:27:57 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:53454 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753242AbeFTB1y (ORCPT ); Tue, 19 Jun 2018 21:27:54 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w5K1OJ2D028572; Wed, 20 Jun 2018 01:27:52 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2017-10-26; bh=rP3T8I/vM1bLwQBZDRD7Fv7r4xkmbv61vpG/KRfDXjM=; b=eFlOgAyWFWdOfbBhWcaWk1SWD47L5EyjiH/8A4EYEbN4FJAszldpgxoj18xYKxY57s8C DkMX53avLQgjE2yfgJyXAeMX/o6HeMNZQQaE2kTIbFaUOlU/Th0pYkuU5iyZVgk6HVcj D9VGhb9aJB9hDjaO4SZT3El42+LGe8Wx02KxtrFpxh6v6r2EnQe3WiqTMsbWwqbSEjj1 JHztSCrWdWcbTkM/RAHAYwgH0Svy0lOiYzV/NOnUsiHwy9aXLuDdBcBYVOkkR6SmJac4 szguon8gL/aS2lRFb79UvhiRliOhj7puFU65/2BonTUfDtN/8WMaz/aAQScBzQWL4UGq 2w== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by aserp2120.oracle.com with ESMTP id 2jmtgwted5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Jun 2018 01:27:52 +0000 Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w5K1RpL4031961 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Jun 2018 01:27:51 GMT Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w5K1RpZT012501; Wed, 20 Jun 2018 01:27:51 GMT Received: from [10.182.69.179] (/10.182.69.179) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 19 Jun 2018 18:27:51 -0700 Subject: Re: [PATCH] blk-mq: use blk_mq_timeout_work to limit the max timeout To: Bart Van Assche , "axboe@kernel.dk" Cc: "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" References: <1529391610-1654-1-git-send-email-jianchao.w.wang@oracle.com> <884a5cbb5622ca5c890585a8d5dff0e3a1d60cfe.camel@wdc.com> From: "jianchao.wang" Message-ID: Date: Wed, 20 Jun 2018 09:28:10 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <884a5cbb5622ca5c890585a8d5dff0e3a1d60cfe.camel@wdc.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8929 signatures=668702 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1805220000 definitions=main-1806200014 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Bart Thanks for your kindly response. On 06/19/2018 11:18 PM, Bart Van Assche wrote: > On Tue, 2018-06-19 at 15:00 +0800, Jianchao Wang wrote: >> blk_rq_timeout is needed to limit the max timeout value, otherwise, >> a idle hctx cannot be deactivated timely in shared-tag case. >> >> Fixes: 12f5b931 (blk-mq: Remove generation seqeunce) >> Signed-off-by: Jianchao Wang >> --- >> block/blk-mq.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/block/blk-mq.c b/block/blk-mq.c >> index 70c65bb..ccebe7b 100644 >> --- a/block/blk-mq.c >> +++ b/block/blk-mq.c >> @@ -868,7 +868,7 @@ static void blk_mq_timeout_work(struct work_struct *work) >> blk_mq_queue_tag_busy_iter(q, blk_mq_check_expired, &next); >> >> if (next != 0) { >> - mod_timer(&q->timeout, next); >> + mod_timer(&q->timeout, blk_rq_timeout(round_jiffies_up(next))); >> } else { >> /* >> * Request timeouts are handled as a forward rolling timer. If > > Hello Jianchao, > > What makes you think that it would be necessary to call blk_rq_timeout() from > blk_mq_timeout_work()? Have you noticed that blk_add_timer() already calls that > function? I think it is not necessary to call blk_rq_timeout() from > blk_mq_timeout_work() because it is guaranteed in that function that the next > timeout is less than BLK_MAX_TIMEOUT jiffies in the future. > blk_add_timer will not re-arm the timer if the timer's expire value is before the new rq's expire value. Let's look at the following scenario. 0 +30s |__________________|___| T0 T1 T2 T1 = T2 - 1 jiffies T0: rq_a is issued and q->timer is armed and will expire at T2 then rq_a is completed. T1: rq_b is issued and q->timer is not re-armed, because its next expire time is T2 < (T1 + 30s) T2: if rq_b have not been completed when timer expires at T2, timer would be re-armed based on the rq_b If we don't have blk_rq_timerout here, the next expire time is about T2 + 30s. This is not good for sharing-tag case. Thanks Jianchao > >