Re: [Xen-devel] [PATCH 2/4] x86/mwait_idle: Allow limiting the sub C-state

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.06.14 at 17:04, <ross.lagerwall@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/acpi/cpu_idle.c
> +++ b/xen/arch/x86/acpi/cpu_idle.c
> @@ -106,6 +106,8 @@ static uint64_t (*__read_mostly tick_to_ns)(uint64_t) = 
> acpi_pm_tick_to_ns;
>  void (*__read_mostly pm_idle_save)(void);
>  unsigned int max_cstate __read_mostly = ACPI_PROCESSOR_MAX_POWER - 1;
>  integer_param("max_cstate", max_cstate);
> +unsigned int max_substate __read_mostly = ACPI_PROCESSOR_MAX_POWER - 1;

For max_cstate this same initializer makes sense, but for the maximum
sub-state it doesn't. I supposed this should simply be UINT_MAX.

> +integer_param("max_substate", max_substate);

As said before, I'd much prefer staying with just max_cstate. Simply
make this a custom_param() and have the sub-state be specified
after an optional comma.

Furthermore you then only alter mwait-idle.c to obey this, while you
leave the ACPI-based driver alone.

Jan


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