Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751970AbdHHEXk (ORCPT ); Tue, 8 Aug 2017 00:23:40 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:33324 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750736AbdHHEXi (ORCPT ); Tue, 8 Aug 2017 00:23:38 -0400 Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 10.3 \(3273\)) Subject: Re: [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression From: Nadav Amit In-Reply-To: <20170808022830.GA28570@bbox> Date: Mon, 7 Aug 2017 21:23:34 -0700 Cc: kernel test robot , "open list:MEMORY MANAGEMENT" , LKML , Andrew Morton , Ingo Molnar , Russell King , Tony Luck , Martin Schwidefsky , "David S. Miller" , Heiko Carstens , Yoshinori Sato , Jeff Dike , linux-arch@vger.kernel.org, lkp@01.org Message-Id: <93CA4B47-95C2-43A2-8E92-B142CAB1DAF7@gmail.com> References: <20170802000818.4760-7-namit@vmware.com> <20170808011923.GE25554@yexl-desktop> <20170808022830.GA28570@bbox> To: Minchan Kim X-Mailer: Apple Mail (2.3273) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id v784NkfI029655 Content-Length: 1608 Lines: 44 Minchan Kim wrote: > Hi, > > On Tue, Aug 08, 2017 at 09:19:23AM +0800, kernel test robot wrote: >> Greeting, >> >> FYI, we noticed a -19.3% regression of will-it-scale.per_process_ops due to commit: >> >> >> commit: 76742700225cad9df49f05399381ac3f1ec3dc60 ("mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem") >> url: https://github.com/0day-ci/linux/commits/Nadav-Amit/mm-migrate-prevent-racy-access-to-tlb_flush_pending/20170802-205715 >> >> >> in testcase: will-it-scale >> on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory >> with following parameters: >> >> nr_task: 16 >> mode: process >> test: brk1 >> cpufreq_governor: performance >> >> test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two. >> test-url: https://github.com/antonblanchard/will-it-scale > > Thanks for the report. > Could you explain what kinds of workload you are testing? > > Does it calls frequently madvise(MADV_DONTNEED) in parallel on multiple > threads? According to the description it is "testcase:brk increase/decrease of one page”. According to the mode it spawns multiple processes, not threads. Since a single page is unmapped each time, and the iTLB-loads increase dramatically, I would suspect that for some reason a full TLB flush is caused during do_munmap(). If I find some free time, I’ll try to profile the workload - but feel free to beat me to it. Nadav