From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f197.google.com (mail-qt0-f197.google.com [209.85.216.197]) by kanga.kvack.org (Postfix) with ESMTP id 757EC6B02F3 for ; Tue, 8 Aug 2017 01:51:05 -0400 (EDT) Received: by mail-qt0-f197.google.com with SMTP id d15so11221196qta.11 for ; Mon, 07 Aug 2017 22:51:05 -0700 (PDT) Received: from mail-qt0-x243.google.com (mail-qt0-x243.google.com. [2607:f8b0:400d:c0d::243]) by mx.google.com with ESMTPS id p31si551340qtp.188.2017.08.07.22.51.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 07 Aug 2017 22:51:04 -0700 (PDT) Received: by mail-qt0-x243.google.com with SMTP id i19so2439701qte.1 for ; Mon, 07 Aug 2017 22:51:04 -0700 (PDT) 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: <93CA4B47-95C2-43A2-8E92-B142CAB1DAF7@gmail.com> Date: Mon, 7 Aug 2017 22:51:00 -0700 Content-Transfer-Encoding: quoted-printable Message-Id: <970B5DC5-BFC2-461E-AC46-F71B3691D301@gmail.com> References: <20170802000818.4760-7-namit@vmware.com> <20170808011923.GE25554@yexl-desktop> <20170808022830.GA28570@bbox> <93CA4B47-95C2-43A2-8E92-B142CAB1DAF7@gmail.com> Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim 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 Nadav Amit wrote: > Minchan Kim wrote: >=20 >> Hi, >>=20 >> On Tue, Aug 08, 2017 at 09:19:23AM +0800, kernel test robot wrote: >>> Greeting, >>>=20 >>> FYI, we noticed a -19.3% regression of will-it-scale.per_process_ops = due to commit: >>>=20 >>>=20 >>> commit: 76742700225cad9df49f05399381ac3f1ec3dc60 ("mm: fix = MADV_[FREE|DONTNEED] TLB flush miss problem") >>> url: = https://github.com/0day-ci/linux/commits/Nadav-Amit/mm-migrate-prevent-rac= y-access-to-tlb_flush_pending/20170802-205715 >>>=20 >>>=20 >>> 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: >>>=20 >>> nr_task: 16 >>> mode: process >>> test: brk1 >>> cpufreq_governor: performance >>>=20 >>> 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 >>=20 >> Thanks for the report. >> Could you explain what kinds of workload you are testing? >>=20 >> Does it calls frequently madvise(MADV_DONTNEED) in parallel on = multiple >> threads? >=20 > According to the description it is "testcase:brk increase/decrease of = one > page=E2=80=9D. According to the mode it spawns multiple processes, not = threads. >=20 > 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(). >=20 > If I find some free time, I=E2=80=99ll 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? Having said that it appears that cpumask_any_but() is really inefficient since it does not have an optimization for the case in which small_const_nbits(nbits)=3D=3Dtrue. When I find some free time, I=E2=80=99= ll try to deal with it. Thanks, Nadav= -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org