linux-kernel - Re: [RFC PATCH 5/5] mm: shmem: add anonymous share mTHP counters

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Date: Tue, 23 Apr 2024 09:46:17 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Barry Song <21cnbao@...il.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org,
 david@...hat.com, wangkefeng.wang@...wei.com, ryan.roberts@....com,
 ying.huang@...el.com, shy828301@...il.com, ziy@...dia.com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 5/5] mm: shmem: add anonymous share mTHP counters



On 2024/4/23 09:17, Barry Song wrote:
> On Mon, Apr 22, 2024 at 3:03 PM Baolin Wang
> <baolin.wang@...ux.alibaba.com> wrote:
>>
>> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>> ---
>>   include/linux/huge_mm.h | 2 ++
>>   mm/huge_memory.c        | 4 ++++
>>   mm/shmem.c              | 5 ++++-
>>   3 files changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>> index 26b6fa98d8ac..67b9c1acad31 100644
>> --- a/include/linux/huge_mm.h
>> +++ b/include/linux/huge_mm.h
>> @@ -270,6 +270,8 @@ enum mthp_stat_item {
>>          MTHP_STAT_ANON_SWPOUT,
>>          MTHP_STAT_ANON_SWPOUT_FALLBACK,
>>          MTHP_STAT_ANON_SWPIN_REFAULT,
>> +       MTHP_STAT_SHMEM_ANON_ALLOC,
>> +       MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK,
> 
> not quite sure about this. for 2MB pmd-mapped THP shmem, we count them
> as FILE_THP.
> here we are counting as SHMEM_ANON. To me, SHMEM_ANON is more correct but
> it doesn't align with pmd-mapped THP. David, Ryan, what do you think?

Thanks for reviewing.

IMO, I think both approaches are acceptable, which also reflects the 
dual nature of anonymous shared pages: on the one hand they are 
anonymous pages, and on the other hand, they are backed by a pseudo 
file. From the user's perspective, I prefer to use the term "anonymous 
shmem", which can be distinguished from the real file-backed THP.

Anyway, let's see what others think.

>>          __MTHP_STAT_COUNT
>>   };
>>
>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>> index 9e52c0db7580..dc15240c1ab3 100644
>> --- a/mm/huge_memory.c
>> +++ b/mm/huge_memory.c
>> @@ -557,6 +557,8 @@ DEFINE_MTHP_STAT_ATTR(anon_alloc_fallback, MTHP_STAT_ANON_ALLOC_FALLBACK);
>>   DEFINE_MTHP_STAT_ATTR(anon_swpout, MTHP_STAT_ANON_SWPOUT);
>>   DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_SWPOUT_FALLBACK);
>>   DEFINE_MTHP_STAT_ATTR(anon_swpin_refault, MTHP_STAT_ANON_SWPIN_REFAULT);
>> +DEFINE_MTHP_STAT_ATTR(shmem_anon_alloc, MTHP_STAT_SHMEM_ANON_ALLOC);
>> +DEFINE_MTHP_STAT_ATTR(shmem_anon_alloc_fallback, MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK);
>>
>>   static struct attribute *stats_attrs[] = {
>>          &anon_alloc_attr.attr,
>> @@ -564,6 +566,8 @@ static struct attribute *stats_attrs[] = {
>>          &anon_swpout_attr.attr,
>>          &anon_swpout_fallback_attr.attr,
>>          &anon_swpin_refault_attr.attr,
>> +       &shmem_anon_alloc_attr.attr,
>> +       &shmem_anon_alloc_fallback_attr.attr,
>>          NULL,
>>   };
>>
>> diff --git a/mm/shmem.c b/mm/shmem.c
>> index 8b009e7040b2..4a0aa75ab29c 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -1706,11 +1706,14 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
>>                          pages = 1 << order;
>>                          index = round_down(index, pages);
>>                          folio = shmem_alloc_hugefolio(gfp, info, index, order);
>> -                       if (folio)
>> +                       if (folio) {
>> +                               count_mthp_stat(order, MTHP_STAT_SHMEM_ANON_ALLOC);
>>                                  goto allocated;
>> +                       }
>>
>>                          if (pages == HPAGE_PMD_NR)
>>                                  count_vm_event(THP_FILE_FALLBACK);
>> +                       count_mthp_stat(order, MTHP_STAT_SHMEM_ANON_ALLOC_FALLBACK);
>>                          order = next_order(&orders, order);
>>                  }
>>          } else {
>> --
>> 2.39.3
>>
> 
> Thanks
> Barry