[LSF/MM/BPF TOPIC] Scalable Pagefaults

[LSF/MM/BPF TOPIC] Scalable Pagefaults

[Matthew Wilcox]

We should continue the conversation from last year on the topic of page
fault scalability.  I presume that by the time of the conference Suren's
current patches for per-VMA locks [1] [2] will be at least in Andrew's
tree, even if not quite upstream yet.  We will then be in a good place
to discuss enhancements:

 - File-backed VMAs
 - UFFD
 - Swap
 - Improve performance for low-thread-count apps
 - Full RCU handling of (some) page faults

Suren Baghdasaryan, Liam Howlett, Michel Lespinasse, Laurent Dufour,
Peter Xu would all be good participants.

[1] https://lore.kernel.org/linux-mm/20230216051750.3125598-1-surenb@google.com/
[2] https://lwn.net/Articles/906852/

Re: [LSF/MM/BPF TOPIC] Scalable Pagefaults

[Liam R. Howlett]

* Matthew Wilcox <willy@infradead.org> [230217 15:14]:
> We should continue the conversation from last year on the topic of page
> fault scalability.  I presume that by the time of the conference Suren's
> current patches for per-VMA locks [1] [2] will be at least in Andrew's
> tree, even if not quite upstream yet.  We will then be in a good place
> to discuss enhancements:
> 
>  - File-backed VMAs
>  - UFFD
>  - Swap
>  - Improve performance for low-thread-count apps
>  - Full RCU handling of (some) page faults

A few other enhancements that we should discuss:

 - Adding protection of detached VMAs to mmap_lock page fault handler
 - Using detached VMAs to stop stack expansion and allow mmap_write_lock
   to downgrade regardless of surrounding VMAs.
 - Fast mmap_write_downgrade by using detached VMAs in other code paths.

> 
> Suren Baghdasaryan, Liam Howlett, Michel Lespinasse, Laurent Dufour,
> Peter Xu would all be good participants.
> 
> [1] https://lore.kernel.org/linux-mm/20230216051750.3125598-1-surenb@google.com/
> [2] https://lwn.net/Articles/906852/
> 
>