On 2024-12-03 06:13, Corinna Vinschen wrote:
On Dec 3 10:20, Christian Franke wrote:
Brian Inglis wrote:
On 2024-12-02 11:28, ASSI wrote:
Christian Franke writes:
+ nice value sched_priority Windows priority class
+ 12...19 1....6 IDLE_PRIORITY_CLASS
+ 4...11 7...12 BELOW_NORMAL_PRIORITY_CLASS
+ -4....3 13...18 NORMAL_PRIORITY_CLASS
+ -12...-5 19...24 ABOVE_NORMAL_PRIORITY_CLASS
+ -13..-19 25...30 HIGH_PRIORITY_CLASS
+ -20 31...32 REALTIME_PRIORITY_CLASS
That mapping looks odd… care to explain why the number of nice values
and sched_priorities doesn't match up for each priority class? 39
possible values for one can't match to 32 for the other of course, but
which ones are skipped and why?
See also miscfuncs.cc which maps nice<->winprio with a 40 entry table,
and cygwin-doc proc(5) or cygwin-ug-net/proc.html which explains the
mapping to scheduler priorities and policies.
No *_PRIORITY_CLASS is mentioned in current newlib-cygwin/winsup/doc/*.
Also relevant may be man-pages-posix sched.h(0p), man-pages-linux
sched(7) and proc_pid_stat(5).
You may also wish to consider whether SCHED_SPORADIC should be somewhat
supported for POSIX compatibility, and SCHED_IDLE, SCHED_BATCH,
SCHED_DEADLINE for Linux compatibility?
SCHED_IDLE: Ignore nice value and set IDLE_PRIORITY_CLASS ?
Would make sense, I guess.
SCHED_BATCH: Reduced mapping, e.g. nice=0 -> BELOW_NORMAL_PRIORITY_CLASS ?
Sounds good.
SCHED_SPORADIC, SCHED_DEADLINE: ?
We can't model SCHED_DEADLINE in Windows.
The current newlib/libc/include/sys/sched.h only defines SCHED_OTHER,
SCHED_FIFO, SCHED_RR and SCHED_SPORADIC. The latter is guarded by
_POSIX_SPORADIC_SERVER which is only set for RTEMS (#ifdef __rtems__) in
features.h.
SCHED_SPORADIC is a bit of a problem. It requires extension of the
sched_param struct with values we're not able to handle.
=> SCHED_IDLE?
Could be something like a background process on a real time system?
Also, SCHED_SPORADIC doesn't exist in Linux either, so why bother.
https://pubs.opengroup.org/onlinepubs/9799919799/
sched.h Change History:
"Sporadic server members are added to the sched_param structure, and the
SCHED_SPORADIC scheduling policy is added for alignment with IEEE Std 1003.1d-1999."
It's been in POSIX since at least Issue 6 thru 8, with no changes in last go
round, so presumably it exists and is used on some major platform(s)?
--
Take care. Thanks, Brian Inglis Calgary, Alberta, Canada
La perfection est atteinte Perfection is achieved
non pas lorsqu'il n'y a plus rien à ajouter not when there is no more to add
mais lorsqu'il n'y a plus rien à retirer but when there is no more to cut
-- Antoine de Saint-Exupéry
