cpuidle:powernv: Make the snooze timeout dynamic.

[Michael Ellerman]

On Thu, 2018-05-31 at 12:15:09 UTC, "Gautham R. Shenoy" wrote:
> From: "Gautham R. Shenoy" <ego at linux.vnet.ibm.com>
> 
> The commit 78eaa10f027c ("cpuidle: powernv/pseries: Auto-promotion of
> snooze to deeper idle state") introduced a timeout for the snooze idle
> state so that it could be eventually be promoted to a deeper idle
> state. The snooze timeout value is static and set to the target
> residency of the next idle state, which would train the cpuidle
> governor to pick the next idle state eventually.
> 
> The unfortunate side-effect of this is that if the next idle state(s)
> is disabled, the CPU will forever remain in snooze, despite the fact
> that the system is completely idle, and other deeper idle states are
> available.
> 
> This patch fixes the issue by dynamically setting the snooze timeout
> to the target residency of the next enabled state on the device.
> 
> Before Patch
> Reviewed-by: Balbir Singh <bsingharora at gmail.com>
> 
> ==================
> POWER8 : Only nap disabled.
>  $cpupower monitor sleep 30
> sleep took 30.01297 seconds and exited with status 0
>               |Idle_Stats
> PKG |CORE|CPU | snoo | Nap  | Fast
>    0|   8|   0| 96.41|  0.00|  0.00
>    0|   8|   1| 96.43|  0.00|  0.00
>    0|   8|   2| 96.47|  0.00|  0.00
>    0|   8|   3| 96.35|  0.00|  0.00
>    0|   8|   4| 96.37|  0.00|  0.00
>    0|   8|   5| 96.37|  0.00|  0.00
>    0|   8|   6| 96.47|  0.00|  0.00
>    0|   8|   7| 96.47|  0.00|  0.00
> 
> POWER9: Shallow states (stop0lite, stop1lite, stop2lite, stop0, stop1,
> stop2) disabled:
> $cpupower monitor sleep 30
> sleep took 30.05033 seconds and exited with status 0
>               |Idle_Stats
> PKG |CORE|CPU | snoo | stop | stop | stop | stop | stop | stop | stop | stop
>    0|  16|   0| 89.79|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00
>    0|  16|   1| 90.12|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00
>    0|  16|   2| 90.21|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00
>    0|  16|   3| 90.29|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00
> 
> After Patch
> ======================
> POWER8 : Only nap disabled.
> $ cpupower monitor sleep 30
> sleep took 30.01200 seconds and exited with status 0
>               |Idle_Stats
> PKG |CORE|CPU | snoo | Nap  | Fast
>    0|   8|   0| 16.58|  0.00| 77.21
>    0|   8|   1| 18.42|  0.00| 75.38
>    0|   8|   2|  4.70|  0.00| 94.09
>    0|   8|   3| 17.06|  0.00| 81.73
>    0|   8|   4|  3.06|  0.00| 95.73
>    0|   8|   5|  7.00|  0.00| 96.80
>    0|   8|   6|  1.00|  0.00| 98.79
>    0|   8|   7|  5.62|  0.00| 94.17
> 
> POWER9: Shallow states (stop0lite, stop1lite, stop2lite, stop0, stop1,
> stop2) disabled:
> 
> $cpupower monitor sleep 30
> sleep took 30.02110 seconds and exited with status 0
>               |Idle_Stats
> PKG |CORE|CPU | snoo | stop | stop | stop | stop | stop | stop | stop | stop
>    0|   0|   0|  0.69|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  9.39| 89.70
>    0|   0|   1|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.05| 93.21
>    0|   0|   2|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00| 89.93
>    0|   0|   3|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00|  0.00| 93.26
> 
> Signed-off-by: Gautham R. Shenoy <ego at linux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/0a4ec6aa035a52c422eceb2ed51ed8

cheers