Re: [PATCH v3 2/2] mm/damon: introduce DAMOS filter type hugepage

[Usama Arif <usamaarif642@gmail.com>]

On 20/01/2025 18:57, David Hildenbrand wrote:
> On 20.01.25 19:19, Usama Arif wrote:
>> This is to gather statistics to check if memory regions of specific
>> access tempratures are backed by hugepages. This includes both THPs
>> and hugetlbfs.
>> This filter can help to observe and prove the effectivenes of
>> different schemes for shrinking/collapsing hugepages.
>>
>> Signed-off-by: Usama Arif <usamaarif642@gmail.com>
>> ---
>> v2 -> v3:
>> - expose hugepage via sysfs even if the kernel is
>>    built without hugepage support. DAMON will just
>>    just return 0. (SJ Park)
>>
>> v1 -> v2:
>> - Wrap DAMOS_FILTER_TYPE_HUGEPAGE case with
>>    CONFIG_PGTABLE_HAS_HUGE_LEAVES (SJ Park)
>> ---
>>   include/linux/damon.h    | 2 ++
>>   mm/damon/paddr.c         | 5 +++++
>>   mm/damon/sysfs-schemes.c | 1 +
>>   3 files changed, 8 insertions(+)
>>
>> diff --git a/include/linux/damon.h b/include/linux/damon.h
>> index af525252b853..1d94d7d88b36 100644
>> --- a/include/linux/damon.h
>> +++ b/include/linux/damon.h
>> @@ -326,6 +326,7 @@ struct damos_stat {
>>    * @DAMOS_FILTER_TYPE_ANON:    Anonymous pages.
>>    * @DAMOS_FILTER_TYPE_MEMCG:    Specific memcg's pages.
>>    * @DAMOS_FILTER_TYPE_YOUNG:    Recently accessed pages.
>> + * @DAMOS_FILTER_TYPE_HUGEPAGE:    Page is part of a hugepage.
>>    * @DAMOS_FILTER_TYPE_ADDR:    Address range.
>>    * @DAMOS_FILTER_TYPE_TARGET:    Data Access Monitoring target.
>>    * @NR_DAMOS_FILTER_TYPES:    Number of filter types.
>> @@ -345,6 +346,7 @@ enum damos_filter_type {
>>       DAMOS_FILTER_TYPE_ANON,
>>       DAMOS_FILTER_TYPE_MEMCG,
>>       DAMOS_FILTER_TYPE_YOUNG,
>> +    DAMOS_FILTER_TYPE_HUGEPAGE,
>>       DAMOS_FILTER_TYPE_ADDR,
>>       DAMOS_FILTER_TYPE_TARGET,
>>       NR_DAMOS_FILTER_TYPES,
>> diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
>> index c0ccf4fade24..224308140441 100644
>> --- a/mm/damon/paddr.c
>> +++ b/mm/damon/paddr.c
>> @@ -222,6 +222,11 @@ static bool damos_pa_filter_match(struct damos_filter *filter,
>>           if (matched)
>>               damon_folio_mkold(folio);
>>           break;
>> +#if defined(CONFIG_PGTABLE_HAS_HUGE_LEAVES)
>> +    case DAMOS_FILTER_TYPE_HUGEPAGE:
>> +        matched = folio_size(folio) == HPAGE_PMD_SIZE;
> 
> 
> Can we directly embed in the name and the comments/docs that we are only talking about PMD size (both, THP and hugetlb)?
> 
> DAMOS_FILTER_TYPE_PMD_HUGEPAGE or sth. like that.
> 
> 

I always think of gigantic page as PUD size, hugepage as PMD size (and not anything smaller), mTHP as smaller than PMD :)
But I don't think thats the official term or standardized across the kernel.  

I can send a v4, or maybe Andrew could apply the diff below?

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 1d94d7d88b36..261c0741dd0f 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -326,7 +326,7 @@ struct damos_stat {
  * @DAMOS_FILTER_TYPE_ANON:    Anonymous pages.
  * @DAMOS_FILTER_TYPE_MEMCG:   Specific memcg's pages.
  * @DAMOS_FILTER_TYPE_YOUNG:   Recently accessed pages.
- * @DAMOS_FILTER_TYPE_HUGEPAGE:        Page is part of a hugepage.
+ * @DAMOS_FILTER_TYPE_PMD_HUGEPAGE:    Page is part of a hugepage (THP/hugetlb).
  * @DAMOS_FILTER_TYPE_ADDR:    Address range.
  * @DAMOS_FILTER_TYPE_TARGET:  Data Access Monitoring target.
  * @NR_DAMOS_FILTER_TYPES:     Number of filter types.
@@ -346,7 +346,7 @@ enum damos_filter_type {
        DAMOS_FILTER_TYPE_ANON,
        DAMOS_FILTER_TYPE_MEMCG,
        DAMOS_FILTER_TYPE_YOUNG,
-       DAMOS_FILTER_TYPE_HUGEPAGE,
+       DAMOS_FILTER_TYPE_PMD_HUGEPAGE,
        DAMOS_FILTER_TYPE_ADDR,
        DAMOS_FILTER_TYPE_TARGET,
        NR_DAMOS_FILTER_TYPES,
diff --git a/mm/damon/paddr.c b/mm/damon/paddr.c
index 224308140441..e374ea952308 100644
--- a/mm/damon/paddr.c
+++ b/mm/damon/paddr.c
@@ -223,7 +223,7 @@ static bool damos_pa_filter_match(struct damos_filter *filter,
                        damon_folio_mkold(folio);
                break;
 #if defined(CONFIG_PGTABLE_HAS_HUGE_LEAVES)
-       case DAMOS_FILTER_TYPE_HUGEPAGE:
+       case DAMOS_FILTER_TYPE_PMD_HUGEPAGE:
                matched = folio_size(folio) == HPAGE_PMD_SIZE;
                break;
 #endif