[PATCH] sched/core: Call wq_worker_tick() for the execution context

[Hui Su]

wq_worker_tick() accounts CPU time and detects CPU-intensive work for
the kworker that is actually running. With proxy execution, rq->donor
is the scheduling context while rq->curr is the execution context.

Calling the hook with rq->donor can skip workqueue accounting when a
kworker is executing on behalf of a donor task. It can also account a
blocked kworker when the donor is a worker but rq->curr is the task
actually executing. The former can delay WORKER_CPU_INTENSIVE handling
and pool concurrency management, which can delay pending kernel work
and userspace operations depending on it.

Use rq->curr for the workqueue tick hook while retaining rq->donor for
scheduler accounting.

Fixes: af0c8b2bf67b ("sched: Split scheduler and execution contexts")
Signed-off-by: Hui Su <sh_def@xxxxxxx>
---
 kernel/sched/core.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f78275192036..a86fd3d88714 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5770,8 +5770,8 @@ void sched_tick(void)
 {
 	int cpu = smp_processor_id();
 	struct rq *rq = cpu_rq(cpu);
-	/* accounting goes to the donor task */
-	struct task_struct *donor;
+	/* scheduler accounting goes to the donor task */
+	struct task_struct *curr, *donor;
 	struct rq_flags rf;
 	unsigned long hw_pressure;
 	u64 resched_latency;
@@ -5782,6 +5782,7 @@ void sched_tick(void)
 	sched_clock_tick();
 
 	rq_lock(rq, &rf);
+	curr = rq->curr;
 	donor = rq->donor;
 
 	psi_account_irqtime(rq, donor, NULL);
@@ -5807,8 +5808,8 @@ void sched_tick(void)
 
 	perf_event_task_tick();
 
-	if (donor->flags & PF_WQ_WORKER)
-		wq_worker_tick(donor);
+	if (curr->flags & PF_WQ_WORKER)
+		wq_worker_tick(curr);
 
 	if (!scx_switched_all()) {
 		rq->idle_balance = idle_cpu(cpu);

base-commit: 89a312991dc6e638a36adc43ccb91dbc25504c04
-- 
2.54.0