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

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Date:   Fri, 16 Jun 2023 15:30:50 +0100
From:   Valentin Schneider <vschneid@...hat.com>
To:     Daniel Bristot de Oliveira <bristot@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        linux-kernel@...r.kernel.org,
        Luca Abeni <luca.abeni@...tannapisa.it>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        Thomas Gleixner <tglx@...utronix.de>,
        Joel Fernandes <joel@...lfernandes.org>,
        Vineeth Pillai <vineeth@...byteword.org>,
        Shuah Khan <skhan@...uxfoundation.org>,
        Daniel Bristot de Oliveira <bristot@...nel.org>
Subject: Re: [RFC PATCH V3 1/6] sched: Unify runtime accounting across classes

On 08/06/23 17:58, Daniel Bristot de Oliveira wrote:
> From: Peter Zijlstra <peterz@...radead.org>
>
> 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@...radead.org>
> Signed-off-by: Daniel Bristot de Oliveira <bristot@...nel.org>

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@...hat.com>

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

---
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);