From: Nadav Amit <nadav.amit@gmail.com>
To: Minchan Kim <minchan@kernel.org>
Cc: kernel test robot <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: Mon, 7 Aug 2017 22:51:00 -0700 [thread overview]
Message-ID: <970B5DC5-BFC2-461E-AC46-F71B3691D301@gmail.com> (raw)
Message-ID: <20170808055100.DFi6894BEOVVVITDy2z9sPT-WjzIniNBNmKSL5sE7os@z> (raw)
In-Reply-To: <93CA4B47-95C2-43A2-8E92-B142CAB1DAF7@gmail.com>
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?
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)==true. When I find some free time, I’ll try to deal
with it.
Thanks,
Nadav
next prev parent reply other threads:[~2017-08-08 5:51 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 [this message]
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
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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