From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id C3D086B025F for ; Tue, 8 Aug 2017 04:08:25 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id w187so27757070pgb.10 for ; Tue, 08 Aug 2017 01:08:25 -0700 (PDT) Received: from lgeamrelo11.lge.com (LGEAMRELO11.lge.com. [156.147.23.51]) by mx.google.com with ESMTP id 3si555253plm.81.2017.08.08.01.08.23 for ; Tue, 08 Aug 2017 01:08:24 -0700 (PDT) Date: Tue, 8 Aug 2017 17:08:21 +0900 From: Minchan Kim Subject: Re: [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression Message-ID: <20170808080821.GA31730@bbox> References: <20170802000818.4760-7-namit@vmware.com> <20170808011923.GE25554@yexl-desktop> <20170808022830.GA28570@bbox> <93CA4B47-95C2-43A2-8E92-B142CAB1DAF7@gmail.com> <970B5DC5-BFC2-461E-AC46-F71B3691D301@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <970B5DC5-BFC2-461E-AC46-F71B3691D301@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Nadav Amit 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 On Mon, Aug 07, 2017 at 10:51:00PM -0700, Nadav Amit wrote: > Nadav Amit wrote: > > > 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 > > pagea??. 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, Ia??ll try to profile the workload - but feel free > > to beat me to it. > > The root-cause appears to be that tlb_finish_mmu() does not call > dec_tlb_flush_pending() - as it should. Any chance you can take care of it? Oops, but with second looking, it seems it's not my fault. ;-) https://marc.info/?l=linux-mm&m=150156699114088&w=2 Anyway, thanks for the pointing out. xiaolong.ye, could you retest with this fix?