Re: [PATCH] mm/numa_balancing: Teach mpol_to_str about the balancing mode

[Huang, Ying]

Tvrtko Ursulin <tursulin@xxxxxxxxxx> writes:

> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
>
> If a task has had MPOL_F_NUMA_BALANCING set it is useful to show that in

IIUC, MPOL_F_NUMA_BALANCING works for VMA area via mbind() too.

> procfs. Teach the mpol_to_str helper about its existance and while at it
> update the comment to account for "weighted interleave" when suggesting
> a recommended buffer size.

Otherwise LGTM, Thanks!

Reviewed-by: "Huang, Ying" <ying.huang@xxxxxxxxx>

> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxx>
> References: bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes")
> Cc: Huang Ying <ying.huang@xxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> ---
>  mm/mempolicy.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index aec756ae5637..d147287c4505 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -3293,8 +3293,9 @@ int mpol_parse_str(char *str, struct mempolicy **mpol)
>   * @pol:  pointer to mempolicy to be formatted
>   *
>   * Convert @pol into a string.  If @buffer is too short, truncate the string.
> - * Recommend a @maxlen of at least 32 for the longest mode, "interleave", the
> - * longest flag, "relative", and to display at least a few node ids.
> + * Recommend a @maxlen of at least 42 for the longest mode, "weighted
> + * interleave", the longest flag, "balancing", and to display at least a few
> + * node ids.
>   */
>  void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
>  {
> @@ -3331,12 +3332,15 @@ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
>  		p += snprintf(p, buffer + maxlen - p, "=");
>  
>  		/*
> -		 * Currently, the only defined flags are mutually exclusive
> +		 * The below two flags are mutually exclusive:
>  		 */
>  		if (flags & MPOL_F_STATIC_NODES)
>  			p += snprintf(p, buffer + maxlen - p, "static");
>  		else if (flags & MPOL_F_RELATIVE_NODES)
>  			p += snprintf(p, buffer + maxlen - p, "relative");
> +
> +		if (flags & MPOL_F_NUMA_BALANCING)
> +			p += snprintf(p, buffer + maxlen - p, "balancing");
>  	}
>  
>  	if (!nodes_empty(nodes))