Re: [RFC 3/4] sched/idle: Disable idle call on least latency requirements

Pavan Kondeti
2020-05-08T08:36:16Z

On Thu, May 07, 2020 at 07:07:22PM +0530, Parth Shah wrote:
> Restrict the call to deeper idle states when the given CPU has been set for
> the least latency requirements
>
> Signed-off-by: Parth Shah <parth@linux.ibm.com>
> ---
> kernel/sched/idle.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
> index b743bf38f08f..85d72a6e2521 100644
> --- a/kernel/sched/idle.c
> +++ b/kernel/sched/idle.c
> @@ -262,7 +262,8 @@ static void do_idle(void)
> * broadcast device expired for us, we don't want to go deep
> * idle as we know that the IPI is going to arrive right away.
> */
> - if (cpu_idle_force_poll || tick_check_broadcast_expired()) {
> + if (cpu_idle_force_poll || tick_check_broadcast_expired() ||
> + per_cpu(nr_lat_sensitive, cpu)) {
> tick_nohz_idle_restart_tick();
> cpu_idle_poll();
> } else {
> --
> 2.17.2
>

Since nr_lat_sensitive updates can happen remotely (when a latency sensitive
task becomes non-latency sensitive task), we may need to add this condition
in cpu_idle_poll() as well.

Thanks,
Pavan
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