+ mm-vmstat-use-xchg-in-cpu_vm_stats_fold.patch added to mm-unstable branch

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The patch titled
     Subject: mm/vmstat: use xchg in cpu_vm_stats_fold
has been added to the -mm mm-unstable branch.  Its filename is
     mm-vmstat-use-xchg-in-cpu_vm_stats_fold.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-vmstat-use-xchg-in-cpu_vm_stats_fold.patch

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: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Subject: mm/vmstat: use xchg in cpu_vm_stats_fold
Date: Fri, 03 Mar 2023 16:58:50 -0300

In preparation to switch vmstat shepherd to flush per-CPU counters
remotely, use xchg instead of a pair of read/write instructions.

Link: https://lkml.kernel.org/r/20230303195908.977788434@xxxxxxxxxx
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Cc: Aaron Tomlin <atomlin@xxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: "Russell King (Oracle)" <linux@xxxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---


--- a/mm/vmstat.c~mm-vmstat-use-xchg-in-cpu_vm_stats_fold
+++ a/mm/vmstat.c
@@ -883,7 +883,7 @@ static int refresh_cpu_vm_stats(void)
 }
 
 /*
- * Fold the data for an offline cpu into the global array.
+ * Fold the data for a cpu into the global array.
  * There cannot be any access by the offline cpu and therefore
  * synchronization is simplified.
  */
@@ -904,8 +904,7 @@ void cpu_vm_stats_fold(int cpu)
 			if (pzstats->vm_stat_diff[i]) {
 				int v;
 
-				v = pzstats->vm_stat_diff[i];
-				pzstats->vm_stat_diff[i] = 0;
+				v = xchg(&pzstats->vm_stat_diff[i], 0);
 				atomic_long_add(v, &zone->vm_stat[i]);
 				global_zone_diff[i] += v;
 			}
@@ -915,8 +914,7 @@ void cpu_vm_stats_fold(int cpu)
 			if (pzstats->vm_numa_event[i]) {
 				unsigned long v;
 
-				v = pzstats->vm_numa_event[i];
-				pzstats->vm_numa_event[i] = 0;
+				v = xchg(&pzstats->vm_numa_event[i], 0);
 				zone_numa_event_add(v, zone, i);
 			}
 		}
@@ -932,8 +930,7 @@ void cpu_vm_stats_fold(int cpu)
 			if (p->vm_node_stat_diff[i]) {
 				int v;
 
-				v = p->vm_node_stat_diff[i];
-				p->vm_node_stat_diff[i] = 0;
+				v = xchg(&p->vm_node_stat_diff[i], 0);
 				atomic_long_add(v, &pgdat->vm_stat[i]);
 				global_node_diff[i] += v;
 			}
_

Patches currently in -mm which might be from mtosatti@xxxxxxxxxx are

mm-vmstat-remove-remote-node-draining.patch
this_cpu_cmpxchg-arm64-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch
this_cpu_cmpxchg-loongarch-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch
this_cpu_cmpxchg-s390-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch
this_cpu_cmpxchg-x86-switch-this_cpu_cmpxchg-to-locked-add-_local-function.patch
add-this_cpu_cmpxchg_local-and-asm-generic-definitions.patch
convert-this_cpu_cmpxchg-users-to-this_cpu_cmpxchg_local.patch
mm-vmstat-switch-counter-modification-to-cmpxchg.patch
mm-vmstat-use-xchg-in-cpu_vm_stats_fold.patch
mm-vmstat-switch-vmstat-shepherd-to-flush-per-cpu-counters-remotely.patch
mm-vmstat-refresh-stats-remotely-instead-of-via-work-item.patch




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