Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752614AbdHIB00 (ORCPT ); Tue, 8 Aug 2017 21:26:26 -0400 Received: from mga06.intel.com ([134.134.136.31]:59125 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752486AbdHIB0Z (ORCPT ); Tue, 8 Aug 2017 21:26:25 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,346,1498546800"; d="scan'208";a="297598555" Date: Wed, 9 Aug 2017 09:25:19 +0800 From: Ye Xiaolong To: Minchan Kim Cc: Nadav Amit , "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 Subject: Re: [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression Message-ID: <20170809012519.GB29499@yexl-desktop> 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> <20170808080821.GA31730@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170808080821.GA31730@bbox> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3165 Lines: 89 On 08/08, Minchan Kim wrote: >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 >> > 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. >> >> 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? Sure, I'll provide the result later. Thanks, Xiaolong > >From 83012114c9cd9304f0d55d899bb4b9329d0e22ac Mon Sep 17 00:00:00 2001 >From: Minchan Kim >Date: Tue, 8 Aug 2017 17:05:19 +0900 >Subject: [PATCH] mm: decrease tlb flush pending count in tlb_finish_mmu > >The tlb pending count increased by tlb_gather_mmu should be decreased >at tlb_finish_mmu. Otherwise, A lot of TLB happens which makes >performance regression. > >Signed-off-by: Minchan Kim >--- > mm/memory.c | 1 + > 1 file changed, 1 insertion(+) > >diff --git a/mm/memory.c b/mm/memory.c >index 34b1fcb829e4..ad2617552f55 100644 >--- a/mm/memory.c >+++ b/mm/memory.c >@@ -423,6 +423,7 @@ void tlb_finish_mmu(struct mmu_gather *tlb, > bool force = mm_tlb_flush_nested(tlb->mm); > > arch_tlb_finish_mmu(tlb, start, end, force); >+ dec_tlb_flush_pending(tlb->mm); > } > > /* >-- >2.7.4 >