Re: [PATCH 0/4] move per-vma lock into vm_area_struct

Davidlohr Bueso
2024-11-11T22:37:36Z

On Mon, 11 Nov 2024, Suren Baghdasaryan wrote:

>To minimize memory overhead, vm_lock implementation is changed from
>using rw_semaphore (40 bytes) to an atomic (8 bytes) and several
>vm_area_struct members are moved into the last cacheline, resulting
>in a less fragmented structure:

I am not a fan of building a custom lock, replacing a standard one.
How much do we really care about this? rwsems are quite optimized
and are known to heavily affect mm performance altogether.

...

>Performance measurements using pft test on x86 do not show considerable
>difference, on Pixel 6 running Android it results in 3-5% improvement in
>faults per second.

pft is a very micro benchmark, these results do not justify this change, imo.

Thanks,
Davidlohr