From: Minchan Kim <minchan@kernel.org>
To: Ye Xiaolong <xiaolong.ye@intel.com>
Cc: Nadav Amit <nadav.amit@gmail.com>,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>,
Russell King <linux@armlinux.org.uk>,
Tony Luck <tony.luck@intel.com>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
"David S. Miller" <davem@davemloft.net>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Jeff Dike <jdike@addtoit.com>,
linux-arch@vger.kernel.org, lkp@01.org
Subject: Re: [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression
Date: Thu, 10 Aug 2017 13:13:53 +0900 [thread overview]
Message-ID: <20170810041353.GB2042@bbox> (raw)
In-Reply-To: <20170809025902.GA17616@yexl-desktop>
On Wed, Aug 09, 2017 at 10:59:02AM +0800, Ye Xiaolong wrote:
> On 08/08, Minchan Kim wrote:
> >On Mon, Aug 07, 2017 at 10:51:00PM -0700, Nadav Amit wrote:
> >> Nadav Amit <nadav.amit@gmail.com> wrote:
> >>
> >> > Minchan Kim <minchan@kernel.org> 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?
> >
>
> I've queued tests for 5 times and results show this patch (e8f682574e4 "mm:
> decrease tlb flush pending count in tlb_finish_mmu") does help recover the
> performance back.
>
> 378005bdbac0a2ec 76742700225cad9df49f053993 e8f682574e45b6406dadfffeb4
> ---------------- -------------------------- --------------------------
> %stddev change %stddev change %stddev
> \ | \ | \
> 3405093 -19% 2747088 -2% 3348752 will-it-scale.per_process_ops
> 1280 ± 3% -2% 1257 ± 3% -6% 1207 vmstat.system.cs
> 2702 ± 18% 11% 3002 ± 19% 17% 3156 ± 18% numa-vmstat.node0.nr_mapped
> 10765 ± 18% 11% 11964 ± 19% 17% 12588 ± 18% numa-meminfo.node0.Mapped
> 0.00 ± 47% -40% 0.00 ± 45% -84% 0.00 ± 42% mpstat.cpu.soft%
>
> Thanks,
> Xiaolong
Thanks for the testing!
next prev parent reply other threads:[~2017-08-10 4:13 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20170802000818.4760-1-namit@vmware.com>
2017-08-02 0:08 ` [PATCH v6 4/7] mm: refactoring TLB gathering API Nadav Amit
2017-08-02 0:08 ` Nadav Amit
2017-08-11 9:23 ` Peter Zijlstra
2017-08-11 9:23 ` Peter Zijlstra
2017-08-11 17:12 ` Nadav Amit
2017-08-11 17:12 ` Nadav Amit
2017-08-14 0:49 ` Minchan Kim
2017-08-02 0:08 ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem Nadav Amit
2017-08-02 0:08 ` Nadav Amit
2017-08-08 1:19 ` [lkp-robot] [mm] 7674270022: will-it-scale.per_process_ops -19.3% regression kernel test robot
2017-08-08 2:28 ` Minchan Kim
2017-08-08 2:28 ` Minchan Kim
2017-08-08 4:23 ` Nadav Amit
2017-08-08 4:23 ` Nadav Amit
2017-08-08 5:51 ` Nadav Amit
2017-08-08 5:51 ` Nadav Amit
2017-08-08 8:08 ` Minchan Kim
2017-08-08 8:08 ` Minchan Kim
2017-08-08 8:16 ` Nadav Amit
2017-08-09 1:25 ` Ye Xiaolong
2017-08-09 2:59 ` Ye Xiaolong
2017-08-09 2:59 ` Ye Xiaolong
2017-08-10 4:13 ` Minchan Kim [this message]
2017-08-10 4:13 ` Minchan Kim
2017-08-10 4:14 ` Nadav Amit
2017-08-10 4:14 ` Nadav Amit
2017-08-10 4:20 ` Minchan Kim
2017-08-11 13:30 ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem Peter Zijlstra
2017-08-11 13:30 ` Peter Zijlstra
2017-08-13 6:14 ` Nadav Amit
2017-08-13 6:14 ` Nadav Amit
2017-08-13 12:08 ` Peter Zijlstra
2017-08-13 12:08 ` Peter Zijlstra
2017-08-14 1:26 ` Minchan Kim
2017-08-14 1:26 ` Minchan Kim
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