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FAILED: patch "[PATCH] mm: only re-generate demotion targets when a numa node" failed to apply to 5.16-stable tree

PATCH [email protected] 1 participant 1 message Apr 2, 2022

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The patch below does not apply to the 5.16-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 734c15700cdf9062ae98d8b131c6fe873dfad26d Mon Sep 17 00:00:00 2001
From: Oscar Salvador <[email protected]>
Date: Tue, 22 Mar 2022 14:47:37 -0700
Subject: [PATCH] mm: only re-generate demotion targets when a numa node
changes its N_CPU state

Abhishek reported that after patch [1], hotplug operations are taking roughly double the expected time. [2]

The reason behind is that the CPU callbacks that migrate_on_reclaim_init() sets always call set_migration_target_nodes() whenever a CPU is brought up/down.

But we only care about numa nodes going from having cpus to become cpuless, and vice versa, as that influences the demotion_target order.

We do already have two CPU callbacks (vmstat_cpu_online() and vmstat_cpu_dead()) that check exactly that, so get rid of the CPU callbacks in migrate_on_reclaim_init() and only call set_migration_target_nodes() from vmstat_cpu_{dead,online}() whenever a numa node change its N_CPU state.

[1] https://lore.kernel.org/linux-mm/[email protected]/
[2] https://lore.kernel.org/linux-mm/[email protected]/

[[email protected]: add feedback from Huang Ying]
Link https://lkml.kernel.org/r/[email protected] open here
Link https://lkml.kernel.org/r/[email protected] open here
Fixes 884a6e5d1f93b ("mm/migrate: update node demotion order on hotplug events")
Signed-off-by Oscar Salvador <[email protected]>
Reviewed-by Baolin Wang <[email protected]>
Tested-by Baolin Wang <[email protected]>
Reported-by Abhishek Goel <[email protected]>
Cc Dave Hansen <[email protected]>
Cc "Huang, Ying" <[email protected]>
Cc Abhishek Goel <[email protected]>
Cc <[email protected]>
Signed-off-by Andrew Morton <[email protected]>
Signed-off-by Linus Torvalds <[email protected]>
include/linux/migrate.h +8 -0
index db96e10eb8da..90e75d5a54d6 100644
@@ -48,7 +48,15 @@ int folio_migrate_mapping(struct address_space *mapping,
 		struct folio *newfolio, struct folio *folio, int extra_count);
 
 extern bool numa_demotion_enabled;
+extern void migrate_on_reclaim_init(void);
+#ifdef CONFIG_HOTPLUG_CPU
+extern void set_migration_target_nodes(void);
 #else
+static inline void set_migration_target_nodes(void) {}
+#endif
+#else
+
+static inline void set_migration_target_nodes(void) {}
 
 static inline void putback_movable_pages(struct list_head *l) {}
 static inline int migrate_pages(struct list_head *l, new_page_t new,
mm/migrate.c +10 -37

68 lines not on this page · raw message

mm/vmstat.c +12 -1
index d5cc8d739fac..b75b1a64b54c 100644
@@ -28,6 +28,7 @@
 #include <linux/mm_inline.h>
 #include <linux/page_ext.h>
 #include <linux/page_owner.h>
+#include <linux/migrate.h>
 
 #include "internal.h"
 

@@ -2049,7 +2050,12 @@ static void __init init_cpu_node_state(void)
 static int vmstat_cpu_online(unsigned int cpu)
 {
 	refresh_zone_stat_thresholds();
-	node_set_state(cpu_to_node(cpu), N_CPU);
+
+	if (!node_state(cpu_to_node(cpu), N_CPU)) {
+		node_set_state(cpu_to_node(cpu), N_CPU);
+		set_migration_target_nodes();
+	}
+
 	return 0;
 }
 

@@ -2072,6 +2078,8 @@ static int vmstat_cpu_dead(unsigned int cpu)
 		return 0;
 
 	node_clear_state(node, N_CPU);
+	set_migration_target_nodes();
+
 	return 0;
 }
 

@@ -2103,6 +2111,9 @@ void __init init_mm_internals(void)
 
 	start_shepherd_timer();
 #endif
+#if defined(CONFIG_MIGRATION) && defined(CONFIG_HOTPLUG_CPU)
+	migrate_on_reclaim_init();
+#endif
 #ifdef CONFIG_PROC_FS
 	proc_create_seq("buddyinfo", 0444, NULL, &fragmentation_op);
 	proc_create_seq("pagetypeinfo", 0400, NULL, &pagetypeinfo_op);