Re: [RFC PATCH 10/30] mm: enable page allocation tagging for __get_free_pages and alloc_pages

[Suren Baghdasaryan]

On Wed, Aug 31, 2022 at 3:11 AM Mel Gorman <mgorman@xxxxxxx> wrote:
>
> On Tue, Aug 30, 2022 at 02:48:59PM -0700, Suren Baghdasaryan wrote:
> > Redefine alloc_pages, __get_free_pages to record allocations done by
> > these functions. Instrument deallocation hooks to record object freeing.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx>
> > +#ifdef CONFIG_PAGE_ALLOC_TAGGING
> > +
> >  #include <linux/alloc_tag.h>
> >  #include <linux/page_ext.h>
> >
> > @@ -25,4 +27,37 @@ static inline void pgalloc_tag_dec(struct page *page, unsigned int order)
> >               alloc_tag_sub(get_page_tag_ref(page), PAGE_SIZE << order);
> >  }
> >
> > +/*
> > + * Redefinitions of the common page allocators/destructors
> > + */
> > +#define pgtag_alloc_pages(gfp, order)                                        \
> > +({                                                                   \
> > +     struct page *_page = _alloc_pages((gfp), (order));              \
> > +                                                                     \
> > +     if (_page)                                                      \
> > +             alloc_tag_add(get_page_tag_ref(_page), PAGE_SIZE << (order));\
> > +     _page;                                                          \
> > +})
> > +
>
> Instead of renaming alloc_pages, why is the tagging not done in
> __alloc_pages()? At least __alloc_pages_bulk() is also missed. The branch
> can be guarded with IS_ENABLED.

Hmm. Assuming all the other allocators using __alloc_pages are inlined, that
should work. I'll try that and if that works will incorporate in the
next respin.
Thanks!

I don't think IS_ENABLED is required because the tagging functions are already
defined as empty if the appropriate configs are not enabled. Unless I
misunderstood
your node.

>
> > +#define pgtag_get_free_pages(gfp_mask, order)                                \
> > +({                                                                   \
> > +     struct page *_page;                                             \
> > +     unsigned long _res = _get_free_pages((gfp_mask), (order), &_page);\
> > +                                                                     \
> > +     if (_res)                                                       \
> > +             alloc_tag_add(get_page_tag_ref(_page), PAGE_SIZE << (order));\
> > +     _res;                                                           \
> > +})
> > +
>
> Similar, the tagging could happen in a core function instead of a wrapper.
>
> > +#else /* CONFIG_PAGE_ALLOC_TAGGING */
> > +
> > +#define pgtag_alloc_pages(gfp, order) _alloc_pages(gfp, order)
> > +
> > +#define pgtag_get_free_pages(gfp_mask, order) \
> > +     _get_free_pages((gfp_mask), (order), NULL)
> > +
> > +#define pgalloc_tag_dec(__page, __size)              do {} while (0)
> > +
> > +#endif /* CONFIG_PAGE_ALLOC_TAGGING */
> > +
> >  #endif /* _LINUX_PGALLOC_TAG_H */
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index b73d3248d976..f7e6d9564a49 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> > @@ -2249,7 +2249,7 @@ EXPORT_SYMBOL(vma_alloc_folio);
> >   * flags are used.
> >   * Return: The page on success or NULL if allocation fails.
> >   */
> > -struct page *alloc_pages(gfp_t gfp, unsigned order)
> > +struct page *_alloc_pages(gfp_t gfp, unsigned int order)
> >  {
> >       struct mempolicy *pol = &default_policy;
> >       struct page *page;
> > @@ -2273,7 +2273,7 @@ struct page *alloc_pages(gfp_t gfp, unsigned order)
> >
> >       return page;
> >  }
> > -EXPORT_SYMBOL(alloc_pages);
> > +EXPORT_SYMBOL(_alloc_pages);
> >
> >  struct folio *folio_alloc(gfp_t gfp, unsigned order)
> >  {
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index e5486d47406e..165daba19e2a 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -763,6 +763,7 @@ static inline bool pcp_allowed_order(unsigned int order)
> >
> >  static inline void free_the_page(struct page *page, unsigned int order)
> >  {
> > +
> >       if (pcp_allowed_order(order))           /* Via pcp? */
> >               free_unref_page(page, order);
> >       else
>
> Spurious wide-space change.
>
> --
> Mel Gorman
> SUSE Labs