Re: [RFC PATCH 02/12] khugepaged: Generalize alloc_charge_folio()

[Dev Jain <dev.jain@xxxxxxx>]

On 17/12/24 8:21 am, Baolin Wang wrote:
> On 2024/12/17 00:50, Dev Jain wrote:
> > Pass order to alloc_charge_folio() and update mTHP statistics.
> >
> > Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
> > ---
> >   include/linux/huge_mm.h |  2 ++
> >   mm/huge_memory.c        |  4 ++++
> >   mm/khugepaged.c         | 13 +++++++++----
> >   3 files changed, 15 insertions(+), 4 deletions(-)
> >
> > diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> > index 93e509b6c00e..8b6d0fed99b3 100644
> > --- a/include/linux/huge_mm.h
> > +++ b/include/linux/huge_mm.h
> > @@ -119,6 +119,8 @@ enum mthp_stat_item {
> >       MTHP_STAT_ANON_FAULT_ALLOC,
> >       MTHP_STAT_ANON_FAULT_FALLBACK,
> >       MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
> > +    MTHP_STAT_ANON_COLLAPSE_ALLOC,
> > +    MTHP_STAT_ANON_COLLAPSE_ALLOC_FAILED,
> >       MTHP_STAT_ZSWPOUT,
> >       MTHP_STAT_SWPIN,
> >       MTHP_STAT_SWPIN_FALLBACK,
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 2da5520bfe24..2e582fad4c77 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -615,6 +615,8 @@ static struct kobj_attribute _name##_attr = 
> > __ATTR_RO(_name)
> >   DEFINE_MTHP_STAT_ATTR(anon_fault_alloc, MTHP_STAT_ANON_FAULT_ALLOC);
> >   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback, 
> > MTHP_STAT_ANON_FAULT_FALLBACK);
> >   DEFINE_MTHP_STAT_ATTR(anon_fault_fallback_charge, 
> > MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE);
> > +DEFINE_MTHP_STAT_ATTR(anon_collapse_alloc, 
> > MTHP_STAT_ANON_COLLAPSE_ALLOC);
> > +DEFINE_MTHP_STAT_ATTR(anon_collapse_alloc_failed, 
> > MTHP_STAT_ANON_COLLAPSE_ALLOC_FAILED);
> >   DEFINE_MTHP_STAT_ATTR(zswpout, MTHP_STAT_ZSWPOUT);
> >   DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
> >   DEFINE_MTHP_STAT_ATTR(swpin_fallback, MTHP_STAT_SWPIN_FALLBACK);
> > @@ -636,6 +638,8 @@ static struct attribute *anon_stats_attrs[] = {
> >       &anon_fault_alloc_attr.attr,
> >       &anon_fault_fallback_attr.attr,
> >       &anon_fault_fallback_charge_attr.attr,
> > +    &anon_collapse_alloc_attr.attr,
> > +    &anon_collapse_alloc_failed_attr.attr,
> >   #ifndef CONFIG_SHMEM
> >       &zswpout_attr.attr,
> >       &swpin_attr.attr,
> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> > index 95643e6e5f31..02cd424b8e48 100644
> > --- a/mm/khugepaged.c
> > +++ b/mm/khugepaged.c
> > @@ -1073,21 +1073,26 @@ static int __collapse_huge_page_swapin(struct 
> > mm_struct *mm,
> >   }
> >     static int alloc_charge_folio(struct folio **foliop, struct 
> > mm_struct *mm,
> > -                  struct collapse_control *cc)
> > +                  int order, struct collapse_control *cc)
> >   {
> >       gfp_t gfp = (cc->is_khugepaged ? 
> > alloc_hugepage_khugepaged_gfpmask() :
> >                GFP_TRANSHUGE);
> >       int node = hpage_collapse_find_target_node(cc);
> >       struct folio *folio;
> >   -    folio = __folio_alloc(gfp, HPAGE_PMD_ORDER, node, 
> > &cc->alloc_nmask);
> > +    folio = __folio_alloc(gfp, order, node, &cc->alloc_nmask);
> >       if (!folio) {
> >           *foliop = NULL;
> >           count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
> > +        if (order != HPAGE_PMD_ORDER)
> > +            count_mthp_stat(order, 
> > MTHP_STAT_ANON_COLLAPSE_ALLOC_FAILED);
> >           return SCAN_ALLOC_HUGE_PAGE_FAIL;
> >       }
> >         count_vm_event(THP_COLLAPSE_ALLOC);
> > +    if (order != HPAGE_PMD_ORDER)
> > +        count_mthp_stat(order, MTHP_STAT_ANON_COLLAPSE_ALLOC);
>
> File collapse will also call alloc_charge_folio() to allocate THP, so 
> using term '_ANON_' is not suitable for both anon and file collapse.

But currently file collapse will only allocate a PMD-folio, and I have 
extended to mTHP only for anon, so it makes sense? Although
I get your point in general...