Re: [PATCH v2 2/2] mm/damon: introduce DAMOS filter type hugepage

[SeongJae Park <sj@kernel.org>]

On Mon, 20 Jan 2025 10:16:50 +0000 Usama Arif <usamaarif642@gmail.com> 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>
> ---
> v1 -> v2:
> - Wrap DAMOS_FILTER_TYPE_HUGEPAGE case with
>   CONFIG_PGTABLE_HAS_HUGE_LEAVES (SJ Park)
> ---
>  include/linux/damon.h    | 4 ++++
>  mm/damon/paddr.c         | 5 +++++
>  mm/damon/sysfs-schemes.c | 3 +++
>  3 files changed, 12 insertions(+)
> 
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index af525252b853..b0dbf380ab76 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 +346,9 @@ enum damos_filter_type {
>  	DAMOS_FILTER_TYPE_ANON,
>  	DAMOS_FILTER_TYPE_MEMCG,
>  	DAMOS_FILTER_TYPE_YOUNG,
> +#if defined(CONFIG_PGTABLE_HAS_HUGE_LEAVES)
> +	DAMOS_FILTER_TYPE_HUGEPAGE,
> +#endif

I'd prefer not enclosing this part with CONFIG_PGTABLE_HAS_HUGE_LEAVES, so that
users can simply use it.  If the config is not set, damos_pa_filter_match()
will just say nothing is hugepage, and hence will work sanely, in my opinion.

>  	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;
> +		break;
> +#endif

This part looks good to me.

>  	default:
>  		break;
>  	}
> diff --git a/mm/damon/sysfs-schemes.c b/mm/damon/sysfs-schemes.c
> index 98f93ae9f59e..3eb3ec464591 100644
> --- a/mm/damon/sysfs-schemes.c
> +++ b/mm/damon/sysfs-schemes.c
> @@ -329,6 +329,9 @@ static const char * const damon_sysfs_scheme_filter_type_strs[] = {
>  	"anon",
>  	"memcg",
>  	"young",
> +#if defined(CONFIG_PGTABLE_HAS_HUGE_LEAVES)
> +	"hugepage",
> +#endif

Again, I'd prefer not enclosing this part.

>  	"addr",
>  	"target",
>  };
> -- 
> 2.43.5


Thanks,
SJ