Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting

[David Hildenbrand]

On 06.10.21 10:27, Michal Hocko wrote:
> On Tue 05-10-21 23:57:36, John Hubbard wrote:
> [...]
> > 1) Yes, just leave the strings in the kernel, that's simple and
> > it works, and the alternatives don't really help your case nearly
> > enough.
>
> I do not have a strong opinion. Strings are easier to use but they
> are more involved and the necessity of kref approach just underlines
> that. There are going to be new allocations and that always can lead
> to surprising side effects.  These are small (80B at maximum) so the
> overall footpring shouldn't all that large by default but it can grow
> quite large with a very high max_map_count. There are workloads which
> really require the default to be set high (e.g. heavy mremap users). So
> if anything all those should be __GFP_ACCOUNT and memcg accounted.
>
> I do agree that numbers are just much more simpler from accounting,
> performance and implementation POV.

+1

I can understand that having a string can be quite beneficial e.g., when 
dumping mmaps. If only user space knows the id <-> string mapping, that 
can be quite tricky.

However, I also do wonder if there would be a way to standardize/reserve 
ids, such that a given id always corresponds to a specific user. If we 
use an uint64_t for an id, there would be plenty room to reserve ids ...

I'd really prefer if we can avoid using strings and instead using ids.

--
Thanks,

David / dhildenb