linux-kernel - Re: [RFC PATCH v2 1/2] mm/mempolicy: Expose get_il

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Message-ID: <0067568e-a604-46d3-96fd-41b62968a90e@redhat.com>
Date: Mon, 23 Jun 2025 21:14:34 +0200
From: David Hildenbrand <david@...hat.com>
To: Bijan Tabatabai <bijan311@...il.com>, damon@...ts.linux.dev,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc: sj@...nel.org, akpm@...ux-foundation.org, ziy@...dia.com,
 matthew.brost@...el.com, joshua.hahnjy@...il.com, rakie.kim@...com,
 byungchul@...com, gourry@...rry.net, ying.huang@...ux.alibaba.com,
 apopple@...dia.com, bijantabatab@...ron.com, venkataravis@...ron.com,
 emirakhur@...ron.com, ajayjoshi@...ron.com, vtavarespetr@...ron.com
Subject: Re: [RFC PATCH v2 1/2] mm/mempolicy: Expose get_il_weight() to MM

On 20.06.25 20:04, Bijan Tabatabai wrote:
> From: Bijan Tabatabai <bijantabatab@...ron.com>
> 
> This patch exposes get_il_weight() in mm/internal.h. This patch is to
> allow other parts of the MM subsystem, such as DAMON, to make page
> placement decisions based on the global interleave weights.
> 
> Signed-off-by: Bijan Tabatabai <bijantabatab@...ron.com>
> ---
>   mm/internal.h  | 6 ++++++
>   mm/mempolicy.c | 2 +-
>   2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index 3823fb356d3b..b718ebe7cad5 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1169,6 +1169,7 @@ extern int node_reclaim_mode;
>   
>   extern int node_reclaim(struct pglist_data *, gfp_t, unsigned int);
>   extern int find_next_best_node(int node, nodemask_t *used_node_mask);
> +extern u8 get_il_weight(int node);

No new "extern". It's a blast from the past :)

>   #else
>   #define node_reclaim_mode 0
>   
> @@ -1181,6 +1182,11 @@ static inline int find_next_best_node(int node, nodemask_t *used_node_mask)
>   {
>   	return NUMA_NO_NODE;
>   }
> +
> +static inline u8 get_il_weight(int node)
> +{
> +	return 1;
> +}
>   #endif
>   
>   static inline bool node_reclaim_enabled(void)
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 1ff7b2174eb7..b1713430ee9c 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -165,7 +165,7 @@ static unsigned int *node_bw_table;
>    */
>   static DEFINE_MUTEX(wi_state_lock);
>   
> -static u8 get_il_weight(int node)
> +u8 get_il_weight(int node)

The function name is shockingly confusing when used outside this file. 
Do we have some namespace to at least highlight what this is about?

node_interleave_weight() might be a lot clearer?

So maybe let's just rename it to something less confusing as we use it 
from other files.

>   {
>   	struct weighted_interleave_state *state;
>   	u8 weight = 1;


-- 
Cheers,

David / dhildenb