On Tue, 20 Feb 2024 at 07:16, zhaoyang.huang <zhaoyang.huang@xxxxxxxxxx> wrote:
>
> From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
>
> As RT, DL, IRQ time could be deemed as lost time of CFS's task, some
It's lost only if cfs has been actually preempted
> timing value want to know the distribution of how these spread
> approximately by using utilization account value (nivcsw is not enough
> sometimes). This commit would like to introduce a helper function to
> achieve this goal.
>
> eg.
> Effective part of A = Total_time * cpu_util_cfs / cpu_util
>
> Timing value A
> (should be a process last for several TICKs or statistics of a repeadted
> process)
>
> Timing start
> |
> |
> preempted by RT, DL or IRQ
> |\
> | This period time is nonvoluntary CPU give up, need to know how long
> |/
preempted means that a cfs task stops running on the cpu and lets
another rt/dl task or an irq run on the cpu instead. We can't know
that. We know an average ratio of time spent in rt/dl and irq contexts
but not if the cpu was idle or running cfs task
> sched in again
> |
> |
> |
> Timing end
>
> Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
> ---
> include/linux/sched.h | 1 +
> kernel/sched/core.c | 20 ++++++++++++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 77f01ac385f7..99cf09c47f72 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -2318,6 +2318,7 @@ static inline bool owner_on_cpu(struct task_struct *owner)
>
> /* Returns effective CPU energy utilization, as seen by the scheduler */
> unsigned long sched_cpu_util(int cpu);
> +unsigned long cfs_prop_by_util(struct task_struct *tsk, unsigned long val);
> #endif /* CONFIG_SMP */
>
> #ifdef CONFIG_RSEQ
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 802551e0009b..217e2220fdc1 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -7494,6 +7494,26 @@ unsigned long sched_cpu_util(int cpu)
> {
> return effective_cpu_util(cpu, cpu_util_cfs(cpu), ENERGY_UTIL, NULL);
> }
> +
> +/*
> + * Calculate the approximate proportion of timing value consumed in cfs.
> + * The user must be aware of this is done by avg_util which is tracked by
> + * the geometric series as decaying the load by y^32 = 0.5 (unit is 1ms).
> + * That is, only the period last for at least several TICKs or the statistics
> + * of repeated timing value are suitable for this helper function.
> + */
> +unsigned long cfs_prop_by_util(struct task_struct *tsk, unsigned long val)
> +{
> + unsigned int cpu = task_cpu(tsk);
> + struct rq *rq = cpu_rq(cpu);
> + unsigned long util;
> +
> + if (tsk->sched_class != &fair_sched_class)
> + return val;
> + util = cpu_util_rt(rq) + cpu_util_cfs(cpu) + cpu_util_irq(rq) + cpu_util_dl(rq);
This is not correct as irq is not on the same clock domain: look at
effective_cpu_util()
You don't care about idle time ?
> + return min(val, cpu_util_cfs(cpu) * val / util);
> +}
> +
> #endif /* CONFIG_SMP */
>
> /**
> --
> 2.25.1
>
