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Subject[tip: sched/psi] sched/psi: Save percpu memory when !psi_cgroups_enabled
The following commit has been merged into the sched/psi branch of tip:

Commit-ID: e2ad8ab04c5cdfc8dc2f382c45d248ab01dee991
Gitweb: https://git.kernel.org/tip/e2ad8ab04c5cdfc8dc2f382c45d248ab01dee991
Author: Chengming Zhou <zhouchengming@bytedance.com>
AuthorDate: Fri, 26 Aug 2022 00:41:04 +08:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 09 Sep 2022 11:08:31 +02:00

sched/psi: Save percpu memory when !psi_cgroups_enabled

We won't use cgroup psi_group when !psi_cgroups_enabled, so don't
bother to alloc percpu memory and init for it.

Also don't need to migrate task PSI stats between cgroups in
cgroup_move_task().

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/20220825164111.29534-4-zhouchengming@bytedance.com
---
kernel/sched/psi.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index 39463dc..77d53c0 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -201,6 +201,7 @@ void __init psi_init(void)
{
if (!psi_enable) {
static_branch_enable(&psi_disabled);
+ static_branch_disable(&psi_cgroups_enabled);
return;
}

@@ -950,7 +951,7 @@ void psi_memstall_leave(unsigned long *flags)
#ifdef CONFIG_CGROUPS
int psi_cgroup_alloc(struct cgroup *cgroup)
{
- if (static_branch_likely(&psi_disabled))
+ if (!static_branch_likely(&psi_cgroups_enabled))
return 0;

cgroup->psi = kzalloc(sizeof(struct psi_group), GFP_KERNEL);
@@ -968,7 +969,7 @@ int psi_cgroup_alloc(struct cgroup *cgroup)

void psi_cgroup_free(struct cgroup *cgroup)
{
- if (static_branch_likely(&psi_disabled))
+ if (!static_branch_likely(&psi_cgroups_enabled))
return;

cancel_delayed_work_sync(&cgroup->psi->avgs_work);
@@ -996,7 +997,7 @@ void cgroup_move_task(struct task_struct *task, struct css_set *to)
struct rq_flags rf;
struct rq *rq;

- if (static_branch_likely(&psi_disabled)) {
+ if (!static_branch_likely(&psi_cgroups_enabled)) {
/*
* Lame to do this here, but the scheduler cannot be locked
* from the outside, so we move cgroups from inside sched/.
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