The patch titled Subject: mm/numa_balancing: teach mpol_to_str about the balancing mode has been added to the -mm mm-unstable branch. Its filename is mm-numa_balancing-teach-mpol_to_str-about-the-balancing-mode.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Tvrtko Ursulin tvrtko.ursulin@igalia.com Subject: mm/numa_balancing: teach mpol_to_str about the balancing mode Date: Mon, 8 Jul 2024 08:56:32 +0100

Since balancing mode was added in bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes"), it was possible to set this mode but it wouldn't be shown in /proc/<pid>/numa_maps since there was no support for it in the mpol_to_str() helper.

Furthermore, because the balancing mode sets the MPOL_F_MORON flag, it would be displayed as 'default' due a workaround introduced a few years earlier in 8790c71a18e5 ("mm/mempolicy.c: fix mempolicy printing in numa_maps").

To tidy this up we implement two changes:

Replace the MPOL_F_MORON check by pointer comparison against the preferred_node_policy array. By doing this we generalise the current special casing and replace the incorrect 'default' with the correct 'bind' for the mode.

Secondly, we add a string representation and corresponding handling for the MPOL_F_NUMA_BALANCING flag.

With the two changes together we start showing the balancing flag when it is set and therefore complete the fix.

Representation format chosen is to separate multiple flags with vertical bars, following what existed long time ago in kernel 2.6.25. But as between then and now there wasn't a way to display multiple flags, this patch does not change the format in practice.

Some /proc/<pid>/numa_maps output examples:

555559580000 bind=balancing:0-1,3 file=... 555585800000 bind=balancing|static:0,2 file=... 555635240000 prefer=relative:0 file=

Link: https://lkml.kernel.org/r/20240708075632.95857-1-tursulin@igalia.com Signed-off-by: Tvrtko Ursulin tvrtko.ursulin@igalia.com Fixes: bda420b98505 ("numa balancing: migrate on fault among multiple bound nodes") References: 8790c71a18e5 ("mm/mempolicy.c: fix mempolicy printing in numa_maps") Reviewed-by: "Huang, Ying" ying.huang@intel.com Cc: Mel Gorman mgorman@suse.de Cc: Peter Zijlstra peterz@infradead.org Cc: Ingo Molnar mingo@redhat.com Cc: Rik van Riel riel@surriel.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: "Matthew Wilcox (Oracle)" willy@infradead.org Cc: Dave Hansen dave.hansen@intel.com Cc: Andi Kleen ak@linux.intel.com Cc: Michal Hocko mhocko@suse.com Cc: David Rientjes rientjes@google.com Cc: stable@vger.kernel.org [5.12+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/mempolicy.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)

--- a/mm/mempolicy.c~mm-numa_balancing-teach-mpol_to_str-about-the-balancing-mode +++ a/mm/mempolicy.c @@ -3297,8 +3297,9 @@ out: * @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 51 for the longest mode, "weighted + * interleave", plus the longest flag flags, "relative|balancing", and to + * display at least a few node ids. */ void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol) { @@ -3307,7 +3308,10 @@ void mpol_to_str(char *buffer, int maxle unsigned short mode = MPOL_DEFAULT; unsigned short flags = 0;

- if (pol && pol != &default_policy && !(pol->flags & MPOL_F_MORON)) { + if (pol && + pol != &default_policy && + !(pol >= &preferred_node_policy[0] && + pol <= &preferred_node_policy[ARRAY_SIZE(preferred_node_policy) - 1])) { mode = pol->mode; flags = pol->flags; } @@ -3335,12 +3339,18 @@ void mpol_to_str(char *buffer, int maxle p += snprintf(p, buffer + maxlen - p, "=");

/* - * Currently, the only defined flags are mutually exclusive + * Static and relative 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) { + if (!is_power_of_2(flags & MPOL_MODE_FLAGS)) + p += snprintf(p, buffer + maxlen - p, "|"); + p += snprintf(p, buffer + maxlen - p, "balancing"); + } }

if (!nodes_empty(nodes)) _

Patches currently in -mm which might be from tvrtko.ursulin@igalia.com are

mm-numa_balancing-teach-mpol_to_str-about-the-balancing-mode.patch