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=-10.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 6D52BC433E3 for ; Mon, 27 Jul 2020 10:52:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 50D222070B for ; Mon, 27 Jul 2020 10:52:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728169AbgG0Kwo (ORCPT ); Mon, 27 Jul 2020 06:52:44 -0400 Received: from mx2.suse.de ([195.135.220.15]:45466 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726298AbgG0Kwo (ORCPT ); Mon, 27 Jul 2020 06:52:44 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EEA79B632; Mon, 27 Jul 2020 10:52:52 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 8DCE01E12C5; Mon, 27 Jul 2020 12:52:42 +0200 (CEST) Date: Mon, 27 Jul 2020 12:52:42 +0200 From: Jan Kara To: Amir Goldstein Cc: Rong Chen , Jan Kara , LKML , lkp@lists.01.org Subject: Re: [fsnotify] c738fbabb0: will-it-scale.per_process_ops -9.5% regression Message-ID: <20200727105242.GK23179@quack2.suse.cz> References: <20200721001505.GD19262@shao2-debian> <9a2a4086-fbad-b4f8-9c00-2b7606441022@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun 26-07-20 14:52:47, Amir Goldstein wrote: > On Fri, Jul 24, 2020 at 6:47 AM Amir Goldstein wrote: > > > > On Fri, Jul 24, 2020 at 5:45 AM Rong Chen wrote: > > > > > > > > > > > > On 7/21/20 11:59 PM, Amir Goldstein wrote: > > > > On Tue, Jul 21, 2020 at 3:15 AM kernel test robot wrote: > > > >> Greeting, > > > >> > > > >> FYI, we noticed a -9.5% regression of will-it-scale.per_process_ops due to commit: > > > >> > > > >> > > > >> commit: c738fbabb0ff62d0f9a9572e56e65d05a1b34c6a ("fsnotify: fold fsnotify() call into fsnotify_parent()") > > > > Strange, that's a pretty dumb patch moving some inlined code from one > > > > function to > > > > another (assuming there are no fsnotify marks in this test). > > > > > > > > Unless I am missing something the only thing that changes slightly is > > > > an extra d_inode(file->f_path.dentry) deference. > > > > I can get rid of it. > > > > > > > > Is it possible to ask for a re-test with fix patch (attached)? > > > > > > Hi Amir, > > > > > > We failed to apply this patch, could you tell us the base commit or the > > > base branch? > > > > > > > Hi Rong, > > > > The patch is applied on top of the reported offending commit: > > c738fbabb0ff62d0f9a9572e56e65d05a1b34c6a ("fsnotify: fold fsnotify() > > call into fsnotify_parent()") > > > > I pushed it to my github: > > https://github.com/amir73il/linux/commits/for_lkp > > > > FWIW, I tried reproducing the reported regression on a local machine. > > I ran the test twice on each of the branch commits: > > 26dc3d2bff62 fsnotify: pass inode to fsnotify_parent() > c738fbabb0ff fsnotify: fold fsnotify() call into fsnotify_parent() > 71d734103edf fsnotify: Rearrange fast path to minimise overhead when > there is no watcher > 47aaabdedf36 fanotify: Avoid softlockups when reading many events > > Not only did I not observe a regression with the reported commit, > but there was a slight improvement. And then there yet was another > improvement with the fix commit on top of it. I suspect this may be closely related to code generation, code cacheline alignment etc. and thus depends heavily on a particular compiler version and CPU. I've checked the commit myself and I agree it looks innocent so for these reasons, I'm not particularly worried about this regression. Honza -- Jan Kara SUSE Labs, CR