Commit 9f72daf7 authored by Nicolas Saenz Julienne's avatar Nicolas Saenz Julienne Committed by Tejun Heo
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cgroup/cpuset: Avoid memory migration when nodemasks match 



With the introduction of ee9707e8 ("cgroup/cpuset: Enable memory
migration for cpuset v2") attaching a process to a different cgroup will
trigger a memory migration regardless of whether it's really needed.
Memory migration is an expensive operation, so bypass it if the
nodemasks passed to cpuset_migrate_mm() are equal.

Note that we're not only avoiding the migration work itself, but also a
call to lru_cache_disable(), which triggers and flushes an LRU drain
work on every online CPU.

Signed-off-by: default avatarNicolas Saenz Julienne <nsaenzju@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent ee9707e8

kernel/cgroup/cpuset.c

+5 −0
Original line number Diff line number Diff line
@@ -1634,6 +1634,11 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from, 
{

	struct cpuset_migrate_mm_work *mwork;



	if (nodes_equal(*from, *to)) {

		mmput(mm);

		return;

	}



	mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);

	if (mwork) {

		mwork->mm = mm;