Re: [RFC PATCH 16/20] famfs: Add fault counters

[Matthew Wilcox]

On Fri, Feb 23, 2024 at 03:50:33PM -0800, Dan Williams wrote:
> Certainly something like that would have satisified this sanity test use
> case. I will note that mm_account_fault() would need some help to figure
> out the size of the page table entry that got installed. Maybe
> extensions to vm_fault_reason to add VM_FAULT_P*D? That compliments
> VM_FAULT_FALLBACK to indicate whether, for example, the fallback went
> from PUD to PMD, or all the way back to PTE.

ugh, no, it's more complicated than that.  look at the recent changes to
set_ptes().  we can now install PTEs of many different sizes, depending
on the architecture.  someday i look forward to supporting all the page
sizes on parisc (4k, 16k, 64k, 256k, ... 4G)