linux-kernel - Re: [PATCH v5 6/6] mm: shmem: add mTHP counters for anonymous shmem

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Date: Wed, 12 Jun 2024 22:16:20 +0800
From: Lance Yang <ioworker0@...il.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org, 
	david@...hat.com, wangkefeng.wang@...wei.com, ying.huang@...el.com, 
	21cnbao@...il.com, ryan.roberts@....com, shy828301@...il.com, ziy@...dia.com, 
	da.gomez@...sung.com, p.raghav@...sung.com, linux-mm@...ck.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 6/6] mm: shmem: add mTHP counters for anonymous shmem

On Wed, Jun 12, 2024 at 5:28 PM Baolin Wang
<baolin.wang@...ux.alibaba.com> wrote:
>
>
>
> On 2024/6/12 16:04, Lance Yang wrote:
> > Hi Baolin,
> >
> > On Tue, Jun 11, 2024 at 6:11 PM Baolin Wang
> > <baolin.wang@...ux.alibaba.com> wrote:
> >>
> >> Add mTHP counters for anonymous shmem.
> >>
> >> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> >> ---
> >>   include/linux/huge_mm.h |  3 +++
> >>   mm/huge_memory.c        |  6 ++++++
> >>   mm/shmem.c              | 18 +++++++++++++++---
> >>   3 files changed, 24 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> >> index 909cfc67521d..212cca384d7e 100644
> >> --- a/include/linux/huge_mm.h
> >> +++ b/include/linux/huge_mm.h
> >> @@ -281,6 +281,9 @@ enum mthp_stat_item {
> >>          MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
> >>          MTHP_STAT_SWPOUT,
> >>          MTHP_STAT_SWPOUT_FALLBACK,
> >> +       MTHP_STAT_FILE_ALLOC,
> >> +       MTHP_STAT_FILE_FALLBACK,
> >> +       MTHP_STAT_FILE_FALLBACK_CHARGE,
> >>          __MTHP_STAT_COUNT
> >>   };
> >>
> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >> index 1360a1903b66..3fbcd77f5957 100644
> >> --- a/mm/huge_memory.c
> >> +++ b/mm/huge_memory.c
> >> @@ -555,6 +555,9 @@ 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(swpout, MTHP_STAT_SWPOUT);
> >>   DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK);
> >> +DEFINE_MTHP_STAT_ATTR(file_alloc, MTHP_STAT_FILE_ALLOC);
> >> +DEFINE_MTHP_STAT_ATTR(file_fallback, MTHP_STAT_FILE_FALLBACK);
> >> +DEFINE_MTHP_STAT_ATTR(file_fallback_charge, MTHP_STAT_FILE_FALLBACK_CHARGE);
> >>
> >>   static struct attribute *stats_attrs[] = {
> >>          &anon_fault_alloc_attr.attr,
> >> @@ -562,6 +565,9 @@ static struct attribute *stats_attrs[] = {
> >>          &anon_fault_fallback_charge_attr.attr,
> >>          &swpout_attr.attr,
> >>          &swpout_fallback_attr.attr,
> >> +       &file_alloc_attr.attr,
> >> +       &file_fallback_attr.attr,
> >> +       &file_fallback_charge_attr.attr,
> >>          NULL,
> >>   };
> >>
> >> diff --git a/mm/shmem.c b/mm/shmem.c
> >> index f5469c357be6..99bd3c34f0fb 100644
> >> --- a/mm/shmem.c
> >> +++ b/mm/shmem.c
> >> @@ -1773,6 +1773,9 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
> >>
> >>                          if (pages == HPAGE_PMD_NR)
> >>                                  count_vm_event(THP_FILE_FALLBACK);
> >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >> +                       count_mthp_stat(order, MTHP_STAT_FILE_FALLBACK);
> >> +#endif
> >
> > Using the conditional compilation directives here is a bit weird :)
> > Would there be any issues if we were to drop them?
>
> Will cause building errors if CONFIG_TRANSPARENT_HUGEPAGE is not enabled.

Sorry, I got it wrong :p

>
> >
> > Since THP_FILE_FALLBACK is working as expected, MTHP_STAT_FILE_FALLBACK
> > should work as well without the conditional compilation directives, IIUC.
>
> No, you should take a look at how count_mthp_stat() is defined :)

You're correct. count_mthp_stat() does cause a compilation error without them
when CONFIG_TRANSPARENT_HUGEPAGE is not defined.

Thanks,
Lance