On Tue, Jul 23, 2013 at 10:23:57AM +0530, Deepthi Dharwar wrote:
> smt-snooze-delay is a tun-able provided currently on powerpc to delay the
> entry of an idle cpu to NAP state. By default, the value is 100us,
> which is entry criteria for NAP state i.e only if the idle period is
> above 100us it would enter NAP. Value of -1 disables entry into NAP.
> This value can be set either through sysfs, ppc64_cpu util or by
> passing it via kernel command line. Currently this feature is broken
> when the value is passed via the kernel command line.
Has it always been broken? Or just since some commit?
> This patch aims to fix this, by taking the appropriate action
> based on the value after the pseries driver is registered.
> This check is carried on in the back-end driver rather than
> setup_smt_snooze_delay(), as one is not sure if the cpuidle driver
> is even registered when setup routine is executed.
> Also, this fixes re-enabling of NAP states by setting appropriate
> value without having to reboot using smt-snooze-delay parameter.
>
> Also, to note is, smt-snooze-delay is per-cpu variable.
> This can be used to enable/disable NAP on per-cpu
> basis using sysfs but when this variable is passed
> via kernel command line or using the smt-snooze-delay
> it applies to all the cpus. Per-cpu tuning can
> only be done via sysfs.
>
> Signed-off-by: Deepthi Dharwar <deep...@linux.vnet.ibm.com>
> ---
> arch/powerpc/platforms/pseries/processor_idle.c | 34
> ++++++++++++++++++-----
> 1 file changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/processor_idle.c
> b/arch/powerpc/platforms/pseries/processor_idle.c
> index 4644efa0..8133f50 100644
> --- a/arch/powerpc/platforms/pseries/processor_idle.c
> +++ b/arch/powerpc/platforms/pseries/processor_idle.c
> @@ -170,18 +170,36 @@ static struct cpuidle_state
> shared_states[MAX_IDLE_STATE_COUNT] = {
> void update_smt_snooze_delay(int cpu, int residency)
> {
> struct cpuidle_driver *drv = cpuidle_get_driver();
> - struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
> + struct cpuidle_device *dev;
>
> if (cpuidle_state_table != dedicated_states)
> return;
>
> - if (residency < 0) {
> - /* Disable the Nap state on that cpu */
> - if (dev)
> - dev->states_usage[1].disable = 1;
> - } else
> - if (drv)
> + if (!drv)
> + return;
> +
> + if (cpu == -1) {
> + if (residency < 0) {
> + /* Disable NAP on all cpus */
> + drv->states[1].disabled = true;
> + } else {
> drv->states[1].target_residency = residency;
> + drv->states[1].disabled = false;
> + }
> + return;
> + }
> +
> + dev = per_cpu(cpuidle_devices, cpu);
> + if (!dev)
> + return;
> +
> + if (residency < 0)
> + dev->states_usage[1].disable = 1;
> + else {
> + drv->states[1].target_residency = residency;
> + drv->states[1].disabled = false;
> + dev->states_usage[1].disable = 0;
Why are we indexing into all these array with '1' ?
cheers
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