Re: [Xen-devel] [PATCH v4 2/5] build: Hook the schedulers into Kconfig

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.01.16 at 22:22, <jonathan.creekmore@xxxxxxxxx> wrote:
> --- a/xen/common/Kconfig
> +++ b/xen/common/Kconfig
> @@ -51,4 +51,71 @@ config KEXEC
>  
>         If unsure, say Y.
>  
> +# Enable schedulers
> +menu "Schedulers"
> +     visible if EXPERT = "y"

Does "visible if EXPERT" not suffice here?

> +config SCHED_CREDIT
> +     bool "Credit scheduler support"
> +     default y

I continue to think that not making the primary scheduler configurable
would be the better solution to the problems resulting from possibly
all of them getting turned off.

> +config SCHED_CREDIT2
> +     bool "Credit2 scheduler support (EXPERIMENTAL)"
> +     default y
> +     ---help---
> +       The credit2 scheduler is a general purpose scheduler that is
> +       optimized for lower latency and higher VM density.
> +
> +       If unsure, say Y.
> +
> +config SCHED_RTDS
> +     bool "RTDS scheduler support (EXPERIMENTAL)"
> +     default y
> +     ---help---
> +       The RTDS scheduler is a soft and firm real-time scheduler for
> +       multicore, targeted for embedded, automotive, graphics and gaming
> +       in the cloud, and general low-latency workloads.
> +
> +       If unsure, say N.
> +
> +config SCHED_ARINC653
> +     bool "ARINC653 scheduler support (EXPERIMENTAL)"
> +     default y
> +     ---help---
> +       The ARINC653 scheduler is a hard real-time scheduler for single
> +       cores, targeted for avionics, drones, and medical devices.
> +
> +       If unsure, say N.
> +
> +choice
> +     prompt "Default Scheduler?"
> +     default SCHED_CREDIT_DEFAULT if SCHED_CREDIT
> +     default SCHED_CREDIT2_DEFAULT if SCHED_CREDIT2
> +     default SCHED_RTDS_DEFAULT if SCHED_RTDS
> +     default SCHED_ARINC653_DEFAULT if SCHED_ARINC653
> +
> +     config SCHED_CREDIT_DEFAULT
> +             bool "Credit Scheduler" if SCHED_CREDIT
> +     config SCHED_CREDIT2_DEFAULT
> +             bool "Credit2 Scheduler" if SCHED_CREDIT2
> +     config SCHED_RTDS_DEFAULT
> +             bool "RT Scheduler" if SCHED_RTDS
> +     config SCHED_ARINC653_DEFAULT
> +             bool "ARINC653 Scheduler" if SCHED_ARINC653
> +endchoice
> +
> +config SCHED_DEFAULT
> +     string
> +     default "credit" if SCHED_CREDIT_DEFAULT
> +     default "credit2" if SCHED_CREDIT2_DEFAULT
> +     default "rtds" if SCHED_RTDS_DEFAULT
> +     default "arinc653" if SCHED_ARINC653_DEFAULT
> +     default "credit"

What use is this last line?

> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -850,8 +850,13 @@ static inline bool_t is_vcpu_online(const struct vcpu *v)
>      return !test_bit(_VPF_down, &v->pause_flags);
>  }
>  
> +#ifdef CONFIG_SCHED_CREDIT
>  void set_vcpu_migration_delay(unsigned int delay);
>  unsigned int get_vcpu_migration_delay(void);
> +#else
> +static inline void set_vcpu_migration_delay(unsigned int delay) { }
> +static inline unsigned int get_vcpu_migration_delay(void) { return 0; }
> +#endif

I don't think these are appropriate: The respective sysctl sub-ops
would probably better indicate failure to the caller.

Jan


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