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

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Date: Tue, 25 Jun 2024 14:26:05 +0100
From: Tvrtko Ursulin <tursulin@...lia.com>
To: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org,
	kernel-dev@...lia.com,
	Tvrtko Ursulin <tvrtko.ursulin@...lia.com>,
	Huang Ying <ying.huang@...el.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: [PATCH] mm/numa_balancing: Teach mpol_to_str about the balancing mode

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

If a task has had MPOL_F_NUMA_BALANCING set it is useful to show that in
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.

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))
-- 
2.44.0