Re: [PATCH v4 02/16] mm: Batch-copy PTE ranges during fork()

[David Hildenbrand <david@redhat.com>]

[...]

>>>
>>
>> gcc version 13.2.1 20231011 (Red Hat 13.2.1-4) (GCC)
>>
>>  From Fedora 38. So "a bit" newer :P
>>
> 
> I'll retry with newer toolchain.
> 
> FWIW, with the code fix and the original compiler:
> 
> Fork, order-0, Apple M2:
> | kernel                |   mean_rel |   std_rel |
> |:----------------------|-----------:|----------:|
> | mm-unstable           |       0.0% |      0.8% |
> | hugetlb-rmap-cleanups |       1.3% |      2.0% |
> | fork-batching         |       4.3% |      1.0% |
> 
> Fork, order-9, Apple M2:
> | kernel                |   mean_rel |   std_rel |
> |:----------------------|-----------:|----------:|
> | mm-unstable           |       0.0% |      0.8% |
> | hugetlb-rmap-cleanups |       0.9% |      0.9% |
> | fork-batching         |     -37.3% |      1.0% |
> 
> Fork, order-0, Ampere Altra:
> | kernel                |   mean_rel |   std_rel |
> |:----------------------|-----------:|----------:|
> | mm-unstable           |       0.0% |      0.7% |
> | hugetlb-rmap-cleanups |       3.2% |      0.7% |
> | fork-batching         |       5.5% |      1.1% |
> 
> Fork, order-9, Ampere Altra:
> | kernel                |   mean_rel |   std_rel |
> |:----------------------|-----------:|----------:|
> | mm-unstable           |       0.0% |      0.1% |
> | hugetlb-rmap-cleanups |       0.5% |      0.1% |
> | fork-batching         |     -10.4% |      0.1% |
> 

I just gave it another quick benchmark run on that Intel system.

hugetlb-rmap-cleanups -> fork-batching

order-0: 0.014114 -> 0.013848

-1.9%

order-9: 0.014262 -> 0.009410

-34%

Note that I disable SMT and turbo, and pin the test to one CPU, to make 
the results as stable as possible. My kernel config has anything related 
to debugging disabled.

-- 
Cheers,

David / dhildenb