From: Nadav Amit <nadav.amit@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: Ye Xiaolong <xiaolong.ye@intel.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: Wed, 9 Aug 2017 21:14:50 -0700 [thread overview]
Message-ID: <80589593-6F0E-4421-9279-681D5B388100@gmail.com> (raw)
In-Reply-To: <20170810041353.GB2042@bbox>
Minchan Kim <minchan@kernel.org> wrote:
> 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!
Sorry again for screwing your patch, Minchan.
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next prev parent reply other threads:[~2017-08-10 4:14 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-02 0:08 [PATCH v6 0/7] fixes of TLB batching races Nadav Amit
2017-08-02 0:08 ` [PATCH v6 1/7] mm: migrate: prevent racy access to tlb_flush_pending Nadav Amit
2017-08-02 0:08 ` [PATCH v6 2/7] mm: migrate: fix barriers around tlb_flush_pending Nadav Amit
2017-08-02 0:08 ` [PATCH v6 3/7] Revert "mm: numa: defer TLB flush for THP migration as long as possible" Nadav Amit
2017-08-11 10:50 ` Peter Zijlstra
2017-08-02 0:08 ` [PATCH v6 4/7] mm: refactoring TLB gathering API Nadav Amit
2017-08-11 9:23 ` Peter Zijlstra
2017-08-11 17:12 ` Nadav Amit
2017-08-14 0:49 ` Minchan Kim
2017-08-02 0:08 ` [PATCH v6 5/7] mm: make tlb_flush_pending global Nadav Amit
2017-08-02 14:28 ` kbuild test robot
2017-08-02 23:23 ` Minchan Kim
2017-08-02 23:27 ` Andrew Morton
2017-08-02 23:34 ` Minchan Kim
2017-08-03 16:40 ` kbuild test robot
2017-08-02 0:08 ` [PATCH v6 6/7] mm: fix MADV_[FREE|DONTNEED] TLB flush miss problem 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 4:23 ` Nadav Amit
2017-08-08 5:51 ` Nadav Amit
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
2017-08-10 4:13 ` Minchan Kim
2017-08-10 4:14 ` Nadav Amit [this message]
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
2017-08-13 6:14 ` Nadav Amit
2017-08-13 12:08 ` Peter Zijlstra
2017-08-14 1:26 ` Minchan Kim
2017-08-02 0:08 ` [PATCH v6 7/7] mm: fix KSM data corruption Nadav Amit
2017-08-02 23:26 ` [PATCH v6 0/7] fixes of TLB batching races Minchan Kim
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