Re: [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority
* Nicholas Piggin [2017-04-04 09:52:07]: > On Tue, 4 Apr 2017 07:54:12 +1000 > Anton Blanchard wrote: > > > From: Anton Blanchard > > > > 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. > > This looks good. I have HMT_lowest() which does alt feature patching > we can use for pseries and default idle code. Alternatively, if we are going to set priority only once in various other places, HMT_low(); HMT_very_low(); should not add to extra cycles. Let me code that up. --Vaidy
Re: [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority
* Anton Blanchard [2017-04-04 07:54:12]:
> From: Anton Blanchard
>
> 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
Reviewed-by: Vaidyanathan Srinivasan
> ---
> 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
Re: [PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority
On Tue, 4 Apr 2017 07:54:12 +1000 Anton Blanchard wrote: > From: Anton Blanchard > > 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. This looks good. I have HMT_lowest() which does alt feature patching we can use for pseries and default idle code.
[PATCH 1/3] cpuidle: powernv: Don't bounce between low and very low thread priority
From: Anton Blanchard
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
---
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;
--
2.11.0
