Re: [mm/gup] 47e29d32af: phoronix-test-suite.npb.FT.A.total_mop_s -45.0% regression

[John Hubbard <jhubbard@nvidia.com>]

On 11/16/20 6:48 PM, kernel test robot wrote:
> 
> Greeting,
> 
> FYI, we noticed a -45.0% regression of phoronix-test-suite.npb.FT.A.total_mop_s due to commit:
> 

That's a huge slowdown...

> 
> commit: 47e29d32afba11b13efb51f03154a8cf22fb4360 ("mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

...but that commit happened in April, 2020. Surely if this were a serious issue we
would have some other indication...is this worth following up on?? I'm inclined to
ignore it, honestly.

thanks,
-- 
John Hubbard
NVIDIA
> 
> 
> in testcase: phoronix-test-suite
> on test machine: 96 threads Intel(R) Xeon(R) Gold 6252 CPU @ 2.10GHz with 192G memory
> with following parameters:
> 
> 	test: npb-1.3.1
> 	option_a: FT.A
> 	cpufreq_governor: performance
> 	ucode: 0x5002f01
> 
> test-description: The Phoronix Test Suite is the most comprehensive testing and benchmarking platform available that provides an extensible framework for which new tests can be easily added.
> test-url: http://www.phoronix-test-suite.com/
> 
> 
> 
> If you fix the issue, kindly add following tag
> Reported-by: kernel test robot <oliver.sang@intel.com>
> 
> 
> Details are as below:
> -------------------------------------------------------------------------------------------------->
> 
> 
> To reproduce:
> 
>          git clone https://github.com/intel/lkp-tests.git
>          cd lkp-tests
>          bin/lkp install job.yaml  # job file is attached in this email
>          bin/lkp run     job.yaml
> 
> =========================================================================================
> compiler/cpufreq_governor/kconfig/option_a/rootfs/tbox_group/test/testcase/ucode:
>    gcc-9/performance/x86_64-rhel-8.3/FT.A/debian-x86_64-phoronix/lkp-csl-2sp8/npb-1.3.1/phoronix-test-suite/0x5002f01
> 
> commit:
>    3faa52c03f ("mm/gup: track FOLL_PIN pages")
>    47e29d32af ("mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages")
> 
> 3faa52c03f440d1b 47e29d32afba11b13efb51f0315
> ---------------- ---------------------------
>         fail:runs  %reproduction    fail:runs
>             |             |             |
>            1:4          -25%            :4     kmsg.Spurious_LAPIC_timer_interrupt_on_cpu
>           %stddev     %change         %stddev
>               \          |                \
>        4585 ±  2%     -45.0%       2522        phoronix-test-suite.npb.FT.A.total_mop_s
>        1223 ±  4%     +40.2%       1714        phoronix-test-suite.time.percent_of_cpu_this_job_got
> 
> 
>                                                                                  
>                       phoronix-test-suite.npb.FT.A.total_mop_s
>                                                                                  
>    6500 +--------------------------------------------------------------------+
>         |  .+.                      .+.      .+.                             |
>    6000 |.+   +.+.+.++.+.+.+.+.+.+.+   +.+.++   +.+.+.+.+.+.+.+.+.++.+       |
>    5500 |-+                                                           :      |
>         |                                                             :      |
>    5000 |-+                                                            :     |
>    4500 |-+                                                            +.+.+.|
>         |                                                                    |
>    4000 |-+                                                                  |
>    3500 |-+                                                                  |
>         |                                                                    |
>    3000 |-+                                                                  |
>    2500 |-+                                       O   O O                    |
>         | O O O O O OO O   O O O O O   O   O  O     O                        |
>    2000 +--------------------------------------------------------------------+
>                                                                                  
>                                                                                  
> [*] bisect-good sample
> [O] bisect-bad  sample
> 
> 
> 
> Disclaimer:
> Results have been estimated based on internal Intel analysis and are provided
> for informational purposes only. Any difference in system hardware or software
> design or configuration may affect actual performance.
> 
> 
> Thanks,
> Oliver Sang
>