[PATCH] cpuidle: mvebu: update cpuidle thresholds for Armada XP SOCs
Daniel Lezcano
daniel.lezcano at linaro.org
Wed Feb 25 02:01:54 PST 2015
On 02/13/2015 03:55 PM, s. rannou wrote:
> Originally, the thresholds used in the cpuidle driver for Armada SOCs
> were temporarily chosen, leaving room for improvements.
>
> This commit updates the thresholds for the Armada XP SOCs with values
> that positively impact performances:
>
> without patch with patch vendor kernel
> - iperf localhost (gbit/sec) ~3.7 ~6.4 ~5.4
> - ioping tmpfs (iops) ~163k ~206k ~179k
> - ioping tmpfs (mib/s) ~636 ~805 ~699
>
> The idle power consumption is negatively impacted (proportionally less
> than the performance gain), and we are still performing better than
> the vendor kernel here:
>
> without patch with patch vendor kernel
> - power consumption idle (W) ~2.4 ~3.2 ~4.4
> - power consumption busy (W) ~8.6 ~8.3 ~8.6
>
> There is still room for improvement regarding the value of these
> thresholds, they were chosen to mimic the vendor kernel.
>
> This patch only impacts Armada XP SOCs and was tested on Online Labs
> C1 boards. A similar approach can be taken to improve the performances
> of the Armada 370 and Armada 38x SOCs.
>
> Thanks a lot to Thomas Petazzoni, Gregory Clement and Willy Tarreau
> for the discussions and tips around this topic.
Hi Sebastien,
trying to tune the target residency and the exit latency is a good idea
but you can have multiple results. If you increase the exit latency and
the target residency, then the governor will choose a shallow state,
thus improving the performance and degrading the power consumption. If
you reduce the values, then the performance will degrade but the power
saving will increase in an acceptable interval (until going to this
state does not consume more energy).
If you have the possibility, I would suggest to apply the right
methodology to find the right values by using the description in the
wiki page [1]. If you can access to the energy values to enter / exit
the state and the power consumed in each idle state, then you can
mathematically compute the right values.
-- Daniel
[1]
https://wiki.linaro.org/WorkingGroups/PowerManagement/Doc/ComputingTargetResidency
>
> Signed-off-by: Sebastien Rannou <mxs at sbrk.org>
> ---
> drivers/cpuidle/cpuidle-mvebu-v7.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-mvebu-v7.c b/drivers/cpuidle/cpuidle-mvebu-v7.c
> index 38e6861..3716a1f 100644
> --- a/drivers/cpuidle/cpuidle-mvebu-v7.c
> +++ b/drivers/cpuidle/cpuidle-mvebu-v7.c
> @@ -50,17 +50,17 @@ static struct cpuidle_driver armadaxp_idle_driver = {
> .states[0] = ARM_CPUIDLE_WFI_STATE,
> .states[1] = {
> .enter = mvebu_v7_enter_idle,
> - .exit_latency = 10,
> + .exit_latency = 100,
> .power_usage = 50,
> - .target_residency = 100,
> + .target_residency = 1000,
> .name = "MV CPU IDLE",
> .desc = "CPU power down",
> },
> .states[2] = {
> .enter = mvebu_v7_enter_idle,
> - .exit_latency = 100,
> + .exit_latency = 1000,
> .power_usage = 5,
> - .target_residency = 1000,
> + .target_residency = 10000,
> .flags = MVEBU_V7_FLAG_DEEP_IDLE,
> .name = "MV CPU DEEP IDLE",
> .desc = "CPU and L2 Fabric power down",
>
--
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