linux-kernel - Re: [PATCH] mm/numa_balancing: Teach mpol_to

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Date: Wed, 26 Jun 2024 16:48:27 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: Tvrtko Ursulin <tursulin@...lia.com>
Cc: linux-mm@...ck.org,  linux-kernel@...r.kernel.org,
  kernel-dev@...lia.com,  Tvrtko Ursulin <tvrtko.ursulin@...lia.com>,  Mel
 Gorman <mgorman@...e.de>,  Peter Zijlstra <peterz@...radead.org>,  Ingo
 Molnar <mingo@...hat.com>,  Rik van Riel <riel@...riel.com>,  Johannes
 Weiner <hannes@...xchg.org>,  "Matthew Wilcox (Oracle)"
 <willy@...radead.org>,  Dave Hansen <dave.hansen@...el.com>,  Andi Kleen
 <ak@...ux.intel.com>,  Michal Hocko <mhocko@...e.com>,  David Rientjes
 <rientjes@...gle.com>
Subject: Re: [PATCH] mm/numa_balancing: Teach mpol_to_str about the
 balancing mode

Tvrtko Ursulin <tursulin@...lia.com> writes:

> From: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
>
> 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@...el.com>

> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>
> References: bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes")
> Cc: Huang Ying <ying.huang@...el.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Rik van Riel <riel@...riel.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Andi Kleen <ak@...ux.intel.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: David Rientjes <rientjes@...gle.com>
> ---
>  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))