Re: [RFC PATCH 24/37] mm: implement speculative handling in __do_fault()

[Peter Zijlstra]

On Wed, Apr 07, 2021 at 10:27:12PM +0100, Matthew Wilcox wrote:
> Doing I/O without any lock held already works; it just uses the file
> refcount.  It would be better to use a vma refcount, as I already said.

The original workload that I developed SPF for (waaaay back when) was
prefaulting a single huge vma. Using a vma refcount was a total loss
because it resulted in the same cacheline contention that down_read()
was having.

As such, I'm always incredibly sad to see mention of vma refcounts.
They're fundamentally not solving the problem :/