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Subject[PATCH v2 01/10] sched/psi: fix periodic aggregation shut off
Date
We don't want to wake periodic aggregation work back up if the
task change is the aggregation worker itself going to sleep, or
we'll ping-pong forever.

Previously, we would use psi_task_change() in psi_dequeue() when
task going to sleep, so this check was put in psi_task_change().

But commit 4117cebf1a9f ("psi: Optimize task switch inside shared cgroups")
defer task sleep handling to psi_task_switch(), won't go through
psi_task_change() anymore.

So this patch move this check to psi_task_switch().

Fixes: 4117cebf1a9f ("psi: Optimize task switch inside shared cgroups")
Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
---
kernel/sched/psi.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/kernel/sched/psi.c b/kernel/sched/psi.c
index a337f3e35997..115a7e52fa23 100644
--- a/kernel/sched/psi.c
+++ b/kernel/sched/psi.c
@@ -800,7 +800,6 @@ void psi_task_change(struct task_struct *task, int clear, int set)
{
int cpu = task_cpu(task);
struct psi_group *group;
- bool wake_clock = true;
void *iter = NULL;
u64 now;

@@ -810,19 +809,9 @@ void psi_task_change(struct task_struct *task, int clear, int set)
psi_flags_change(task, clear, set);

now = cpu_clock(cpu);
- /*
- * Periodic aggregation shuts off if there is a period of no
- * task changes, so we wake it back up if necessary. However,
- * don't do this if the task change is the aggregation worker
- * itself going to sleep, or we'll ping-pong forever.
- */
- if (unlikely((clear & TSK_RUNNING) &&
- (task->flags & PF_WQ_WORKER) &&
- wq_worker_last_func(task) == psi_avgs_work))
- wake_clock = false;

while ((group = iterate_groups(task, &iter)))
- psi_group_change(group, cpu, clear, set, now, wake_clock);
+ psi_group_change(group, cpu, clear, set, now, true);
}

void psi_task_switch(struct task_struct *prev, struct task_struct *next,
@@ -858,6 +847,7 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,

if (prev->pid) {
int clear = TSK_ONCPU, set = 0;
+ bool wake_clock = true;

/*
* When we're going to sleep, psi_dequeue() lets us
@@ -871,13 +861,23 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
clear |= TSK_MEMSTALL_RUNNING;
if (prev->in_iowait)
set |= TSK_IOWAIT;
+
+ /*
+ * Periodic aggregation shuts off if there is a period of no
+ * task changes, so we wake it back up if necessary. However,
+ * don't do this if the task change is the aggregation worker
+ * itself going to sleep, or we'll ping-pong forever.
+ */
+ if (unlikely((prev->flags & PF_WQ_WORKER) &&
+ wq_worker_last_func(prev) == psi_avgs_work))
+ wake_clock = false;
}

psi_flags_change(prev, clear, set);

iter = NULL;
while ((group = iterate_groups(prev, &iter)) && group != common)
- psi_group_change(group, cpu, clear, set, now, true);
+ psi_group_change(group, cpu, clear, set, now, wake_clock);

/*
* TSK_ONCPU is handled up to the common ancestor. If we're tasked
@@ -886,7 +886,7 @@ void psi_task_switch(struct task_struct *prev, struct task_struct *next,
if (sleep) {
clear &= ~TSK_ONCPU;
for (; group; group = iterate_groups(prev, &iter))
- psi_group_change(group, cpu, clear, set, now, true);
+ psi_group_change(group, cpu, clear, set, now, wake_clock);
}
}
}
--
2.36.1
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