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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_HIGH 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 35000C43142 for ; Tue, 31 Jul 2018 05:19:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DD80E208A3 for ; Tue, 31 Jul 2018 05:19:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="GMW2uuny" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DD80E208A3 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 S1729634AbeGaG6N (ORCPT ); Tue, 31 Jul 2018 02:58:13 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:50900 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726655AbeGaG6M (ORCPT ); Tue, 31 Jul 2018 02:58:12 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w6V5IiAJ062864; Tue, 31 Jul 2018 05:19:43 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-2018-07-02; bh=9cQ0TNneGq4sKOlI4REU00u/TKD7WXNyixK0CuKn3oI=; b=GMW2uunykrsjoCLNGmifkmnUFQP0YElVNjtX1WhMHHQEh6X4SiTZ87mXMehBUM03hCkN +eK6vyzCAyg700oTrPw4rrSYo1k0QXAwQtejQV/uRRl6PEaNEECX/AtJ8O+EUQlyee6E YJPZJ23IByqLet0vVPL6qsnWvbB2/riFZNHc8B9esE55nTmynCGLJXdLPGbDcTeclRgE eXP7600CvM8LXHzgyzx/YsKlgAZ4Ehacdpy5gLsq4qD2RSiRWvT9nEmupZT2UssQyXvh a0jFbK/AjNgi+dPNFbIDnBWahShCHbunlwQd/VJTJIdJGY15Gz7AMteG/DqzCLycNhyx hw== Received: from aserv0021.oracle.com (aserv0021.oracle.com [141.146.126.233]) by aserp2130.oracle.com with ESMTP id 2kge0cycau-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Jul 2018 05:19:43 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserv0021.oracle.com (8.14.4/8.14.4) with ESMTP id w6V5JgQP031642 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 31 Jul 2018 05:19:42 GMT Received: from abhmp0009.oracle.com (abhmp0009.oracle.com [141.146.116.15]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w6V5Jg0m032245; Tue, 31 Jul 2018 05:19:42 GMT Received: from [10.182.69.179] (/10.182.69.179) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 30 Jul 2018 22:19:41 -0700 Subject: Re: [RFC] blk-mq: clean up the hctx restart To: Ming Lei Cc: axboe@kernel.dk, bart.vanassche@wdc.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org References: <1533009735-2221-1-git-send-email-jianchao.w.wang@oracle.com> <20180731045805.GE15701@ming.t460p> From: "jianchao.wang" Message-ID: <8a3383e6-2926-6858-d8f2-671f3cb9e460@oracle.com> Date: Tue, 31 Jul 2018 13:19:42 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180731045805.GE15701@ming.t460p> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8970 signatures=668706 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=8.0.1-1806210000 definitions=main-1807310058 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ming On 07/31/2018 12:58 PM, Ming Lei wrote: > On Tue, Jul 31, 2018 at 12:02:15PM +0800, Jianchao Wang wrote: >> Currently, we will always set SCHED_RESTART whenever there are >> requests in hctx->dispatch, then when request is completed and >> freed the hctx queues will be restarted to avoid IO hang. This >> is unnecessary most of time. Especially when there are lots of >> LUNs attached to one host, the RR restart loop could be very >> expensive. > > The big RR restart loop has been killed in the following commit: > > commit 97889f9ac24f8d2fc8e703ea7f80c162bab10d4d > Author: Ming Lei > Date: Mon Jun 25 19:31:48 2018 +0800 > > blk-mq: remove synchronize_rcu() from blk_mq_del_queue_tag_set() > > Oh, sorry, I didn't look into this patch due to its title when iterated the mail list, therefore I didn't realize the RR restart loop has already been killed. :) The RR restart loop could ensure the fairness of sharing some LLDD resource, not just avoid IO hung. Is it OK to kill it totally ? Thanks Jianchao