Re: [RFC PATCH V3 1/6] sched: Unify runtime accounting across classes

[Valentin Schneider]

On 08/06/23 17:58, Daniel Bristot de Oliveira wrote:
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>
> All classes use sched_entity::exec_start to track runtime and have
> copies of the exact same code around to compute runtime.
>
> Collapse all that.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>

This one's been around for a while, John also carries it for PE [1] because it
makes things simpler. We should just get it in :-)

The three-layered if (unlikely(delta_exec <= 0)) is unfortunate, but I think we
can live with it. Tiny factorization appended below, but regardless:

Reviewed-by: Valentin Schneider <vschneid@xxxxxxxxxx>

[1]: http://lore.kernel.org/r/20230601055846.2349566-2-jstultz@xxxxxxxxxx

---
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e7fcf558dc4bc..e52e609724482 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -914,6 +914,14 @@ static s64 update_curr_se(struct rq *rq, struct sched_entity *curr)
 	return delta_exec;
 }
 
+static inline void
+account_curr_runtime(struct task_struct *curr, s64 runtime, u64 vruntime)
+{
+	trace_sched_stat_runtime(curr, runtime, vruntime);
+	account_group_exec_runtime(curr, runtime);
+	cgroup_account_cputime(curr, runtime);
+}
+
 /*
  * Used by other classes to account runtime.
  */
@@ -926,10 +934,7 @@ s64 update_curr_common(struct rq *rq)
 	if (unlikely(delta_exec <= 0))
 		return delta_exec;
 
-	trace_sched_stat_runtime(curr, delta_exec, 0);
-
-	account_group_exec_runtime(curr, delta_exec);
-	cgroup_account_cputime(curr, delta_exec);
+	account_curr_runtime(curr, delta_exec, 0);
 
 	return delta_exec;
 }
@@ -955,9 +960,7 @@ static void update_curr(struct cfs_rq *cfs_rq)
 	if (entity_is_task(curr)) {
 		struct task_struct *curtask = task_of(curr);
 
-		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
-		cgroup_account_cputime(curtask, delta_exec);
-		account_group_exec_runtime(curtask, delta_exec);
+		account_curr_runtime(curtask, delta_exec, curr->vruntime);
 	}
 
 	account_cfs_rq_runtime(cfs_rq, delta_exec);