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Message-ID: <CAK1f24kj_0DsVYgZj3nH699jt2MN4AQ55w7gGoFaWM_zgceYSQ@mail.gmail.com>
Date: Sun, 24 Nov 2024 14:55:29 +0800
From: Lance Yang <ioworker0@...il.com>
To: Wenchao Hao <haowenchao22@...il.com>
Cc: Barry Song <21cnbao@...il.com>, Jonathan Corbet <corbet@....net>,
Andrew Morton <akpm@...ux-foundation.org>, David Hildenbrand <david@...hat.com>,
Ryan Roberts <ryan.roberts@....com>, Baolin Wang <baolin.wang@...ux.alibaba.com>,
Usama Arif <usamaarif642@...il.com>, Matthew Wilcox <willy@...radead.org>,
Peter Xu <peterx@...hat.com>, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: Re: [PATCH v2] mm: add per-order mTHP swap-in fallback/fallback_charge
counters
On Sat, Nov 23, 2024 at 9:17 PM Wenchao Hao <haowenchao22@...il.com> wrote:
>
> On 2024/11/23 19:52, Lance Yang wrote:
> > On Sat, Nov 23, 2024 at 6:27 PM Barry Song <21cnbao@...il.com> wrote:
> >>
> >> On Sat, Nov 23, 2024 at 10:36 AM Lance Yang <ioworker0@...il.com> wrote:
> >>>
> >>> Hi Wenchao,
> >>>
> >>> On Sat, Nov 23, 2024 at 12:14 AM Wenchao Hao <haowenchao22@...il.com> wrote:
> >>>>
> >>>> Currently, large folio swap-in is supported, but we lack a method to
> >>>> analyze their success ratio. Similar to anon_fault_fallback, we introduce
> >>>> per-order mTHP swpin_fallback and swpin_fallback_charge counters for
> >>>> calculating their success ratio. The new counters are located at:
> >>>>
> >>>> /sys/kernel/mm/transparent_hugepage/hugepages-<size>/stats/
> >>>> swpin_fallback
> >>>> swpin_fallback_charge
> >>>>
> >>>> Signed-off-by: Wenchao Hao <haowenchao22@...il.com>
> >>>> ---
> >>>> V2:
> >>>> Introduce swapin_fallback_charge, which increments if it fails to
> >>>> charge a huge page to memory despite successful allocation.
> >>>>
> >>>> Documentation/admin-guide/mm/transhuge.rst | 10 ++++++++++
> >>>> include/linux/huge_mm.h | 2 ++
> >>>> mm/huge_memory.c | 6 ++++++
> >>>> mm/memory.c | 2 ++
> >>>> 4 files changed, 20 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst
> >>>> index 5034915f4e8e..9c07612281b5 100644
> >>>> --- a/Documentation/admin-guide/mm/transhuge.rst
> >>>> +++ b/Documentation/admin-guide/mm/transhuge.rst
> >>>> @@ -561,6 +561,16 @@ swpin
> >>>> is incremented every time a huge page is swapped in from a non-zswap
> >>>> swap device in one piece.
> >>>>
> >>>
> >>> Would the following be better?
> >>>
> >>> +swpin_fallback
> >>> + is incremented if a huge page swapin fails to allocate or charge
> >>> + it and instead falls back to using small pages.
> >>>
> >>> +swpin_fallback_charge
> >>> + is incremented if a huge page swapin fails to charge it and instead
> >>> + falls back to using small pages even though the allocation was
> >>> + successful.
> >>
> >> much better, but it is better to align with "huge pages with
> >> lower orders or small pages", not necessarily small pages:
> >>
> >> anon_fault_fallback
> >> is incremented if a page fault fails to allocate or charge
> >> a huge page and instead falls back to using huge pages with
> >> lower orders or small pages.
> >>
> >> anon_fault_fallback_charge
> >> is incremented if a page fault fails to charge a huge page and
> >> instead falls back to using huge pages with lower orders or
> >> small pages even though the allocation was successful.
> >
> > Right, I clearly overlooked that ;)
> >
>
> Hi Lance and Barry,
>
> Do you think the following expression is clear? Compared to my original
> version, I’ve removed the word “huge” from the first line, and it now
> looks almost identical to anon_fault_fallback/anon_fault_fallback_charge.
Well, that's fine with me. And let's see Barry's opinion as well ;)
Thanks,
Lance
>
> swpin_fallback
> is incremented if a page swapin fails to allocate or charge
> a huge page and instead falls back to using huge pages with
> lower orders or small pages.
>
> swpin_fallback_charge
> is incremented if a page swapin fails to charge a huge page and
> instead falls back to using huge pages with lower orders or
> small pages even though the allocation was successful.
>
> Thanks,
> Wencaho
>
> > Thanks,
> > Lance
> >
> >>
> >>>
> >>> Thanks,
> >>> Lance
> >>>
> >>>> +swpin_fallback
> >>>> + is incremented if a huge page swapin fails to allocate or charge
> >>>> + a huge page and instead falls back to using huge pages with
> >>>> + lower orders or small pages.
> >>>> +
> >>>> +swpin_fallback_charge
> >>>> + is incremented if a page swapin fails to charge a huge page and
> >>>> + instead falls back to using huge pages with lower orders or
> >>>> + small pages even though the allocation was successful.
> >>>> +
> >>>> swpout
> >>>> is incremented every time a huge page is swapped out to a non-zswap
> >>>> swap device in one piece without splitting.
> >>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> >>>> index b94c2e8ee918..93e509b6c00e 100644
> >>>> --- a/include/linux/huge_mm.h
> >>>> +++ b/include/linux/huge_mm.h
> >>>> @@ -121,6 +121,8 @@ enum mthp_stat_item {
> >>>> MTHP_STAT_ANON_FAULT_FALLBACK_CHARGE,
> >>>> MTHP_STAT_ZSWPOUT,
> >>>> MTHP_STAT_SWPIN,
> >>>> + MTHP_STAT_SWPIN_FALLBACK,
> >>>> + MTHP_STAT_SWPIN_FALLBACK_CHARGE,
> >>>> MTHP_STAT_SWPOUT,
> >>>> MTHP_STAT_SWPOUT_FALLBACK,
> >>>> MTHP_STAT_SHMEM_ALLOC,
> >>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> >>>> index ee335d96fc39..46749dded1c9 100644
> >>>> --- a/mm/huge_memory.c
> >>>> +++ b/mm/huge_memory.c
> >>>> @@ -617,6 +617,8 @@ 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(zswpout, MTHP_STAT_ZSWPOUT);
> >>>> DEFINE_MTHP_STAT_ATTR(swpin, MTHP_STAT_SWPIN);
> >>>> +DEFINE_MTHP_STAT_ATTR(swpin_fallback, MTHP_STAT_SWPIN_FALLBACK);
> >>>> +DEFINE_MTHP_STAT_ATTR(swpin_fallback_charge, MTHP_STAT_SWPIN_FALLBACK_CHARGE);
> >>>> DEFINE_MTHP_STAT_ATTR(swpout, MTHP_STAT_SWPOUT);
> >>>> DEFINE_MTHP_STAT_ATTR(swpout_fallback, MTHP_STAT_SWPOUT_FALLBACK);
> >>>> #ifdef CONFIG_SHMEM
> >>>> @@ -637,6 +639,8 @@ static struct attribute *anon_stats_attrs[] = {
> >>>> #ifndef CONFIG_SHMEM
> >>>> &zswpout_attr.attr,
> >>>> &swpin_attr.attr,
> >>>> + &swpin_fallback_attr.attr,
> >>>> + &swpin_fallback_charge_attr.attr,
> >>>> &swpout_attr.attr,
> >>>> &swpout_fallback_attr.attr,
> >>>> #endif
> >>>> @@ -669,6 +673,8 @@ static struct attribute *any_stats_attrs[] = {
> >>>> #ifdef CONFIG_SHMEM
> >>>> &zswpout_attr.attr,
> >>>> &swpin_attr.attr,
> >>>> + &swpin_fallback_attr.attr,
> >>>> + &swpin_fallback_charge_attr.attr,
> >>>> &swpout_attr.attr,
> >>>> &swpout_fallback_attr.attr,
> >>>> #endif
> >>>> diff --git a/mm/memory.c b/mm/memory.c
> >>>> index 209885a4134f..774dfd309cfe 100644
> >>>> --- a/mm/memory.c
> >>>> +++ b/mm/memory.c
> >>>> @@ -4189,8 +4189,10 @@ static struct folio *alloc_swap_folio(struct vm_fault *vmf)
> >>>> if (!mem_cgroup_swapin_charge_folio(folio, vma->vm_mm,
> >>>> gfp, entry))
> >>>> return folio;
> >>>> + count_mthp_stat(order, MTHP_STAT_SWPIN_FALLBACK_CHARGE);
> >>>> folio_put(folio);
> >>>> }
> >>>> + count_mthp_stat(order, MTHP_STAT_SWPIN_FALLBACK);
> >>>> order = next_order(&orders, order);
> >>>> }
> >>>>
> >>>> --
> >>>> 2.45.0
> >>>>
> >>
> >> Thanks
> >> Barry
>
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