Re: sys/sched.h: Reasonable value of SCHED_BATCH ?

SCHED_SPOTADIC has been in POSIX a long time but does seem to be rarely
implemented. Per change history from the POSIX standard on sched.h:

"the SCHED_SPORADIC scheduling policy is added for alignment with
IEEE Std 1003.1d-1999"

RTEMS and QNX support it but I don't recall any other OSes with
SCHED_SPORADIC.

SCHED_IDLE, SCHED_BATCH,  SCHED_DEADLINE, etc. are bespoke and not in
POSIX. Hopefully they will not be visible except where supported. It looks
like you are doing that.

Others should speak up but I think for Linux, Cygwin, *BSD, etc where
binary compatibility is required, you will need to stick with the values
used now.

--joel

On Mon, Dec 9, 2024 at 8:12 AM Christian Franke <
[email protected]> wrote:

> This is related to this thread on cygwin-patches ML:
> https://sourceware.org/pipermail/cygwin-patches/2024q4/013105.html
>
> Which would be a reasonable integer value for a newly defined SCHED_BATCH ?
>
> Current newlib/libc/include/sys/sched.h:
>
> #if defined(__CYGWIN__) // see c1bfa897
> #define SCHED_OTHER    3
> #else
> #define SCHED_OTHER    0
> #endif
>
> #define SCHED_FIFO     1
> #define SCHED_RR       2
>
> #if defined(_POSIX_SPORADIC_SERVER)// __rtems__ only ?
> #define SCHED_SPORADIC 4
> #endif
>
> #if __GNU_VISIBLE
> #define SCHED_IDLE     5 // Recent addition (61c2f075)
> #endif
>
>
> Linux:
> #define SCHED_OTHER    0
> #define SCHED_FIFO     1
> #define SCHED_RR       2
> #define SCHED_BATCH    3
> /* SCHED_ISO: reserved but not implemented yet */
> #define SCHED_IDLE     5
> #define SCHED_DEADLINE 6
> #define SCHED_EXT      7
>
> FreeBSD:
> #define SCHED_FIFO     1
> #define SCHED_OTHER    2
> #define SCHED_RR       3
>
>
> First alternative: Align non-Cygwin value with Linux
>
> #if __GNU_VISIBLE
> #if defined(__CYGWIN__)
> #define SCHED_BATCH    0
> #else
> #define SCHED_BATCH    3
> #endif
> #endif
>
> Second alternative: Use next free value
>
> #if __GNU_VISIBLE
> ...
> #define SCHED_BATCH    6
> #endif
>
> Any preferences?
>



>
> --
> Regards,
> Christian
>
>