On 8/27/20 2:16 AM, Thomas Zimmermann wrote:
> Hi
>
> Am 26.08.20 um 10:58 schrieb kernel test robot:
>> Greeting,
>>
>> FYI, we noticed a 26.2% improvement of vm-scalability.throughput due to
>> commit:
>
> I guess this resolves the once-measured performance penalty of similar
> magnitude. But do we really understand these tests? When I sent out
> patches to resolve the problem, nothing changed. And suddenly the
> performance is back to normal.
>
> Best regards
> Thomas
>
>>
>>
>> commit: 913ec479bb5cc27f99f24d5fd111b3ef29a4deb9 ("drm/mgag200: Replace VRAM
>> helpers with SHMEM helpers")
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>>
>>
>> in testcase: vm-scalability
>> on test machine: 288 threads Intel(R) Xeon Phi(TM) CPU 7295 @ 1.50GHz with
>> 80G memory
>> with following parameters:
>>
>> runtime: 300s
>> size: 8T
>> test: anon-cow-seq-hugetlb
>> cpufreq_governor: performance
>> ucode: 0x11
Hello Thomas,
Did drm changes really impact anon-cow-seq-hugetlb performance?
My change c0d0381ade79 ("hugetlbfs: use i_mmap_rwsem for more pmd sharing
synchronization") caused a -33.4% regression of anon-cow-seq-hugetlb. A
recent change 34ae204f185 (hugetlbfs: remove call to huge_pte_alloc without
i_mmap_rwsem) was tested by Zhengjun Xing and improved performance by 20
something percent. That seems in line with this report/improvement.
Perhaps the tooling is not always accurate in determining the commit which
causes the performance changes?
Perhaps I am misreading information in the reports?
--
Mike Kravetz
