linux-kernel - Re: [PATCH v2 7/7] mm: shmem: add mTHP counters for anonymous shmem

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Date: Wed, 15 May 2024 11:14:10 +0800
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Lance Yang <ioworker0@...il.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, linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] mm: shmem: add mTHP counters for anonymous shmem



On 2024/5/14 22:49, Lance Yang wrote:
> Hi Baolin,
> 
> On Mon, May 13, 2024 at 1:08 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 b5339210268d..e162498fef82 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_ANON_SWPOUT,
>>          MTHP_STAT_ANON_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 d3080a8843f2..fcda6ae604f6 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(anon_swpout, MTHP_STAT_ANON_SWPOUT);
>>   DEFINE_MTHP_STAT_ATTR(anon_swpout_fallback, MTHP_STAT_ANON_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,
>>          &anon_swpout_attr.attr,
>>          &anon_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 8b020ff09c72..fd2cb2e73a21 100644
>> --- a/mm/shmem.c
>> +++ b/mm/shmem.c
>> @@ -1786,6 +1786,9 @@ 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
> 
> Seems like we don't need these conditional compilation directives here.
> 
> The THP_FILE_FALLBACK above will result in a compilation error if
> CONFIG_TRANSPARENT_HUGEPAGE is not defined. So we don't
> worry about that :)
> 
> See THP_FILE_FALLBACK in include/linux/vm_event_item.h.
> 
>>                          order = next_order(&suitable_orders, order);
>>                  }
>>          } else {
>> @@ -1805,9 +1808,15 @@ static struct folio *shmem_alloc_and_add_folio(struct vm_fault *vmf,
>>                  if (xa_find(&mapping->i_pages, &index,
>>                                  index + pages - 1, XA_PRESENT)) {
>>                          error = -EEXIST;
>> -               } else if (pages == HPAGE_PMD_NR) {
>> -                       count_vm_event(THP_FILE_FALLBACK);
>> -                       count_vm_event(THP_FILE_FALLBACK_CHARGE);
>> +               } else if (pages > 1) {
>> +                       if (pages == HPAGE_PMD_NR) {
>> +                               count_vm_event(THP_FILE_FALLBACK);
>> +                               count_vm_event(THP_FILE_FALLBACK_CHARGE);
>> +                       }
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +                       count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK);
>> +                       count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_FALLBACK_CHARGE);
>> +#endif
> 
> As above.
> 
>>                  }
>>                  goto unlock;
>>          }
>> @@ -2178,6 +2187,9 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
>>                  if (!IS_ERR(folio)) {
>>                          if (folio_test_pmd_mappable(folio))
>>                                  count_vm_event(THP_FILE_ALLOC);
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> +                       count_mthp_stat(folio_order(folio), MTHP_STAT_FILE_ALLOC);
>> +#endif
> 
> As above.
> 
> Perhaps we need to define MTHP_STAT_FILE_ALLOC and friends
> using a same way as THP_FILE_ALLOC, set as '{ BUILD_BUG(); 0; }'
> If CONFIG_TRANSPARENT_HUGEPAGE is not defined.
> 
> Likely:
> 
> #ifndef CONFIG_TRANSPARENT_HUGEPAGE
> #define MTHP_STAT_FILE_ALLOC ({ BUILD_BUG(); 0; })
> ...
> #endif

This is not enough, and we should also define a dummy function for 
count_mthp_stat() when CONFIG_TRANSPARENT_HUGEPAGE is not enabled. I was 
also hesitant about doing this before, but adding macro controls seems 
relatively simple:)

Thanks for reviewing.