linux-kernel - Re: [PATCH v4 5/6] alloc_tag: introduce pgtag_ref

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Message-ID: <CAJuCfpH9yc2kYGZqYjYPWbApy05yqiONqziBQ+qF+R3nZRL56w@mail.gmail.com>
Date: Wed, 23 Oct 2024 14:09:12 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: kent.overstreet@...ux.dev, corbet@....net, arnd@...db.de, 
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Subject: Re: [PATCH v4 5/6] alloc_tag: introduce pgtag_ref_handle to abstract
 page tag references

On Wed, Oct 23, 2024 at 2:00 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed, 23 Oct 2024 10:07:58 -0700 Suren Baghdasaryan <surenb@...gle.com> wrote:
>
> > To simplify later changes to page tag references, introduce new
> > pgtag_ref_handle type. This allows easy replacement of page_ext
> > as a storage of page allocation tags.
> >
> > ...
> >
> >  static inline void pgalloc_tag_copy(struct folio *new, struct folio *old)
> >  {
> > +     union pgtag_ref_handle handle;
> > +     union codetag_ref ref;
> >       struct alloc_tag *tag;
> > -     union codetag_ref *ref;
> >
> >       tag = pgalloc_tag_get(&old->page);
> >       if (!tag)
> >               return;
> >
> > -     ref = get_page_tag_ref(&new->page);
> > -     if (!ref)
> > +     if (!get_page_tag_ref(&new->page, &ref, &handle))
> >               return;
> >
> >       /* Clear the old ref to the original allocation tag. */
> >       clear_page_tag_ref(&old->page);
> >       /* Decrement the counters of the tag on get_new_folio. */
> > -     alloc_tag_sub(ref, folio_nr_pages(new));
> > -
> > -     __alloc_tag_ref_set(ref, tag);
> > -
> > -     put_page_tag_ref(ref);
> > +     alloc_tag_sub(&ref, folio_nr_pages(new));
>
> mm-stable has folio_size(new) here, fixed up.

Oh, right. You merged that patch tonight and I formatted my patchset
yesterday :)
Thanks for the fixup.

>
> I think we aleady discussed this, but there's a crazy amount of
> inlining here.  pgalloc_tag_split() is huge, and has four callsites.

I must have missed that discussion but I am happy to unline this
function. I think splitting is heavy enough operation that this
uninlining would not have be noticeable.
Thanks!