[PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority

[Vaidyanathan Srinivasan]

* Anton Blanchard <anton at ozlabs.org> [2017-04-04 07:54:12]:

> From: Anton Blanchard <anton at samba.org>
> 
> The core of snooze_loop() continually bounces between low and very
> low thread priority. Changing thread priorities is an expensive
> operation that can negatively impact other threads on a core.
> 
> All CPUs that can run PowerNV support very low priority, so we can
> avoid the change completely.
> 
> Signed-off-by: Anton Blanchard <anton at samba.org>

Reviewed-by: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>

> ---
>  drivers/cpuidle/cpuidle-powernv.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/cpuidle/cpuidle-powernv.c b/drivers/cpuidle/cpuidle-powernv.c
> index cda8f62d555b..9d9f164894eb 100644
> --- a/drivers/cpuidle/cpuidle-powernv.c
> +++ b/drivers/cpuidle/cpuidle-powernv.c
> @@ -57,7 +57,6 @@ static int snooze_loop(struct cpuidle_device *dev,
>  	snooze_exit_time = get_tb() + snooze_timeout;
>  	ppc64_runlatch_off();
>  	while (!need_resched()) {
> -		HMT_low();
>  		HMT_very_low();
>  		if (snooze_timeout_en && get_tb() > snooze_exit_time)
>  			break;


HMT_low() is legacy and can be removed for powernv platforms.

--Vaidy