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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=no 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 4C680C2D0C6 for ; Fri, 27 Dec 2019 13:10:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20FDD20740 for ; Fri, 27 Dec 2019 13:10:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726562AbfL0NKb (ORCPT ); Fri, 27 Dec 2019 08:10:31 -0500 Received: from out30-57.freemail.mail.aliyun.com ([115.124.30.57]:54376 "EHLO out30-57.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726053AbfL0NKb (ORCPT ); Fri, 27 Dec 2019 08:10:31 -0500 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R201e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01f04427;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_---0Tm24V6j_1577452226; Received: from JosephdeMacBook-Pro.local(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0Tm24V6j_1577452226) by smtp.aliyun-inc.com(127.0.0.1); Fri, 27 Dec 2019 21:10:27 +0800 From: Joseph Qi Subject: Re: Discussion: is it time to remove dioread_nolock? To: "Theodore Y. Ts'o" , Ext4 Developers List Cc: Liu Bo , Xiaoguang Wang References: <20191226153118.GA17237@mit.edu> Message-ID: Date: Fri, 27 Dec 2019 21:10:26 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20191226153118.GA17237@mit.edu> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Hi Ted, After applying Ritesh's patches, from my test result, there is no obvious performance difference between default mount options and with dioread_lock (delalloc or nodelalloc). I'm not sure if dioread_nolock was used for other purpose in the scenario reported by Bo Liu. Maybe Xiaoguang could give some inputs. Thanks, Joseph On 19/12/26 23:31, Theodore Y. Ts'o wrote: > With inclusion of Ritesh's inode lock scalability patches[1], the > traditional performance reasons for dioread_nolock --- namely, > removing the need to take an exclusive lock for Direct I/O read > operations --- has been removed. > > [1] https://lore.kernel.org/r/20191212055557.11151-1-riteshh@linux.ibm.com > > So... is it time to remove the code which supports dioread_nolock? > Doing so would simplify the code base, and reduce the test matrix. > This would also make it easier to restructure the write path when > allocating blocks so that the extent tree is updated after writing out > the data blocks, by clearing away the underbrush of dioread nolock > first. > > If we do this, we'd leave the dioread_nolock mount option for > backwards compatibility, but it would be a no-op and not actually do > anything. > > Any objections before I look into ripping out dioread_nolock? > > The one possible concern that I considered was for Alibaba, which was > doing something interesting with dioread_nolock plus nodelalloc. But > looking at Liu Bo's explanation[2], I believe that their workload > would be satisfied simply by using the standard ext4 mount options > (that is, the default mode has the performance benefits when doing > parallel DIO reads, and so the need for nodelalloc to mitigate the > tail latency concerns which Alibaba was seeing in their workload would > not be needed). Could Liu or someone from Alibaba confirm, perhaps > with some benchmarks using their workload? > > [2] https://lore.kernel.org/linux-ext4/20181121013035.ab4xp7evjyschecy@US-160370MP2.local/ > > - Ted >