Re: [RFC PATCH v3 1/4] mm/damon: Introduce DAMOS_QUOTA_HUGEPAGE auto tuning

[SeongJae Park <sj@kernel.org>]

On Thu, 4 Jun 2026 15:03:34 +0000 <gutierrez.asier@huawei-partners.com> wrote:

> From: Asier Gutierrez <gutierrez.asier@huawei-partners.com>
> 
> Introduce DAMOS_QUOTA_HUGEPAGE auto tuning Add a
> new DAMOS quota goal metric to measure the amount of huge
> page consumption to total anonymous memory consumption
> ratio.

s/anonymous// ?

> 
> Signed-off-by: Asier Gutierrez <gutierrez.asier@huawei-partners.com>
> ---
>  include/linux/damon.h |  1 +
>  mm/damon/core.c       | 14 ++++++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index c7a31572689b..8e15a674e893 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
> @@ -177,6 +177,7 @@ enum damos_quota_goal_metric {
>  	DAMOS_QUOTA_ACTIVE_MEM_BP,
>  	DAMOS_QUOTA_INACTIVE_MEM_BP,
>  	DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP,
> +	DAMOS_QUOTA_HUGEPAGE,

On the previous revision, I suggested renaming this to
DAMOS_QUOTA_HUGEPAGE_MEM_BP for consistency, but it didn't got your reply.
Could I ask your opinion?

Also, I asked you to add the kernel-doc comment before dropping RFC.  I know
you didn't drop RFC tag yet, but could you consider adding it from the next
revision?

>  	NR_DAMOS_QUOTA_GOAL_METRICS,
>  };
>  
> diff --git a/mm/damon/core.c b/mm/damon/core.c
> index 9f38deddcb30..7fc7477a353a 100644
> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -2536,6 +2536,17 @@ static unsigned int damos_get_in_active_mem_bp(bool active_ratio)
>  	return mult_frac(inactive, 10000, total);
>  }
>  
> +static unsigned int damos_hugepage_mem_bp(void)
> +{
> +	unsigned long thp, total;
> +
> +	thp = global_node_page_state(NR_ANON_THPS) +
> +				global_node_page_state(NR_SHMEM_THPS) +
> +				global_node_page_state(NR_FILE_THPS);
> +	total = totalram_pages() - global_zone_page_state(NR_FREE_PAGES);
> +	return mult_frac(thp, 10000, total);
> +}

As Sashiko also [1] commented, let's avoid divide by zero by checking if total
is zero, before calling mult_frac().

I wouldn't mind ignoring Sashiko's 32-bit concern, but do you have any opinion?

> +
>  static void damos_set_quota_goal_current_value(struct damon_ctx *c,
>  		struct damos *s, struct damos_quota_goal *goal)
>  {
> @@ -2567,6 +2578,9 @@ static void damos_set_quota_goal_current_value(struct damon_ctx *c,
>  		goal->current_value = damos_get_node_eligible_mem_bp(c, s,
>  				goal->nid);
>  		break;
> +	case DAMOS_QUOTA_HUGEPAGE:
> +		goal->current_value = damos_hugepage_mem_bp();
> +		break;
>  	default:
>  		break;
>  	}
> -- 
> 2.43.0

Other than the above comments, looks good to me overall.

[1] https://lore.kernel.org/20260604151932.93C431F00893@smtp.kernel.org


Thanks,
SJ