Commit f68e1480 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Linus Torvalds

mm: reduce atomic use on use_mm fast path

When the mm being switched to matches the active mm, we don't need to
increment and then drop the mm count.  In a simple benchmark this happens
in about 50% of time.  Making that conditional reduces contention on that
cacheline on SMP systems.
Acked-by: default avatarAndrea Arcangeli <>
Signed-off-by: default avatarMichael S. Tsirkin <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 3d2d827f
......@@ -26,12 +26,15 @@ void use_mm(struct mm_struct *mm)
active_mm = tsk->active_mm;
if (active_mm != mm) {
tsk->mm = mm;
tsk->active_mm = mm;
tsk->mm = mm;
switch_mm(active_mm, mm, tsk);
if (active_mm != mm)
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