Re: [PATCH v1 05/11] mm: convert VM_PFNMAP tracking to pfnmap_track() + pfnmap_untrack()

Lorenzo Stoakes
2025-04-28T19:37:43Z

On Mon, Apr 28, 2025 at 07:23:18PM +0200, David Hildenbrand wrote:
> On 28.04.25 18:24, Peter Xu wrote:
> > On Mon, Apr 28, 2025 at 06:16:21PM +0200, David Hildenbrand wrote:
> > > > Probably due to what config you have. E.g., when I'm looking mine it's
> > > > much bigger and already consuming 256B, but it's because I enabled more
> > > > things (userfaultfd, lockdep, etc.).
> > >
> > > Note that I enabled everything that you would expect on a production system
> > > (incld. userfaultfd, mempolicy, per-vma locks), so I didn't enable lockep.
> >
> > I still doubt whether you at least enabled userfaultfd, e.g., your previous
> > paste has:
> >
> > struct vm_userfaultfd_ctx vm_userfaultfd_ctx; /* 176 0 */
> >
> > Not something that matters.. but just in case you didn't use the expected
> > config file you wanted to use..
>
> You're absolutely right. I only briefly rechecked for this purpose here on
> my notebook, and only looked for the existence of members, not expecting
> that we have confusing stuff like vm_userfaultfd_ctx.
>
> I checked again and the size stays at 192 with allyesconfig and then
> disabling debug options.

I think a reasonable case is everything on, except CONFIG_DEBUG_LOCK_ALLOC and I
don't care about nommu.

So:

CONFIG_PER_VMA_LOCK
CONFIG_SWAP
CONFIG_MMU (exclude the nommu vm_region field)
CONFIG_NUMA
CONFIG_NUMA_BALANCING
CONFIG_PER_VMA_LOCK
CONFIG_ANON_VMA_NAME
__HAVE_PFNMAP_TRACKING

So to be clear - allyesconfig w/o debug gives us this yes? And we don't add a
cache line? In which case all good :)

>
> --
> Cheers,
>
> David / dhildenb
>