Hi
Am 27.08.20 um 16:56 schrieb Mike Kravetz:
> 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.Some of DRM's memory management might be affected by hugetable changes. While I cannot really point to a specific location, it's not impossible that there's a connection. > > Perhaps the tooling is not always accurate in determining the commit which > causes the performance changes? > Perhaps I am misreading information in the reports? > From what I remember, some of these tests print to the console, which has always been slow, and has generally been a bad idea for performance tests. I guess these tests are not very accurate. Best regards Thomas -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer
signature.asc
Description: OpenPGP digital signature
