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 EC7B6C433EF for ; Wed, 15 Jun 2022 12:36:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344694AbiFOMgt (ORCPT ); Wed, 15 Jun 2022 08:36:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234067AbiFOMgs (ORCPT ); Wed, 15 Jun 2022 08:36:48 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6BB6530553; Wed, 15 Jun 2022 05:36:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=5lqEWJkgj4WjPMuFW/4um7Uq+N/W4NBmyjYBaPvODgA=; b=vWlkI0pgs/XEbRElbcbobR9x5/ xOMvayvrru8rGx8BcLb04qvMiqqgkWMhtELlE4vNY+qjLMUxNgEEtWtO/hhcWMSO1EWZEFWr8Q0cm 3X17/GtHvRwQu5tuf61wACBzsaHS6LYnEgLUfWJnKqmT+ZvKfU5wl9HgNWHHz5exLvNRwqen5Mw0s V2SrBaA7jP3eptFp4KZ0GhER5exyexHNggeQ46b7nfFNmWWf6nYA+/f5Qq2nT44bguo8RTby7aAqT tNrnkBN90FHFkyE92627IAlUPwaStfjnQHApd1ZZY00MMAldfbrikKBIA4BocCzFLvD+VwdtQhIHY WRZM8qkw==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1o1SGG-0013CA-8o; Wed, 15 Jun 2022 12:36:40 +0000 Date: Wed, 15 Jun 2022 13:36:40 +0100 From: Matthew Wilcox To: Yin Fengwei Cc: kernel test robot , LKML , lkp@lists.01.org, lkp@intel.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Subject: Re: [LKP] Re: [mm/readahead] 793917d997: fio.read_iops -18.8% regression Message-ID: References: <20220418144234.GD25584@xsang-OptiPlex-9020> <1e8deaea-5a05-1846-d51c-b834beb9f23e@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1e8deaea-5a05-1846-d51c-b834beb9f23e@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Jun 15, 2022 at 02:38:24PM +0800, Yin Fengwei wrote: > On 4/19/2022 1:08 AM, Matthew Wilcox wrote: > > > > I'm on holiday today, but adding linux-fsdevel and linux-mm so relevant > > people know about this. > > > > Don't focus on the 18% regression, focus on the 240% improvement on the > > other benchmark ;-) > > > > Seriously, someone (probably me) needs to dig into what the benchmark > > is doing and understand whether there's a way to avoid (or decide this > > regression isn't relevant) while keeping the performance gains elsewhere. > With: > commit b9ff43dd27434dbd850b908e2e0e1f6e794efd9b > Author: Matthew Wilcox (Oracle) > Date: Wed Apr 27 17:01:28 2022 -0400 > > mm/readahead: Fix readahead with large folios > > the regression is almost gone: That makes sense. I did think at the time that this was probably the cause of the problem. > commit: > 18788cfa236967741b83db1035ab24539e2a21bb > b9ff43dd27434dbd850b908e2e0e1f6e794efd9b > > 18788cfa23696774 b9ff43dd27434dbd850b908e2e0 > ---------------- --------------------------- > fail:runs %reproduction fail:runs > | | | > 4698:9 -36360% 1426:3 dmesg.timestamp:last > 3027:9 -22105% 1037:3 kmsg.timestamp:last > %stddev %change %stddev > \ | \ > 0.39 ±253% -0.3 0.09 ±104% fio.latency_1000us% > 0.00 ±141% +0.0 0.01 fio.latency_100ms% > 56.60 ± 5% +10.3 66.92 ± 8% fio.latency_10ms% > 15.65 ± 22% -1.3 14.39 ± 17% fio.latency_20ms% > 1.46 ±106% -0.5 0.95 ± 72% fio.latency_2ms% > 25.81 ± 25% -9.2 16.59 ± 18% fio.latency_4ms% > 0.09 ± 44% +0.9 1.04 ± 22% fio.latency_50ms% > 0.00 ±282% +0.0 0.02 ±141% fio.latency_750us% > 13422 ± 6% -1.4% 13233 fio.read_bw_MBps <----- A stddev of 6% and a decline of 1.4%? How many tests did you run to make sure that this is a real decline and not fluctuation of one-quarter-of-one-standard-devisation?