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.
Patch on top of original patch attached.
SCHED_BATCH: Reduced mapping, e.g. nice=0 -> BELOW_NORMAL_PRIORITY_CLASS ?
Sounds good.
More complex, topic suggests to do some rework of the nice<->winprio
mapping functions first.
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.
Also, SCHED_SPORADIC doesn't exist in Linux either, so why bother.
Let's forget these.
From 0ffa0beb2d4f845b9c3ac6a5be842147163d26a2 Mon Sep 17 00:00:00 2001
From: Christian Franke <christian.fra...@t-online.de>
Date: Tue, 3 Dec 2024 15:42:50 +0100
Subject: [PATCH] Cygwin: sched_setscheduler: accept SCHED_IDLE
Add SCHED_IDLE to <sys/sched.h>. If SCHED_IDLE is selected, preserve
the nice value and set the Windows priority to IDLE_PRIORITY_CLASS.
Signed-off-by: Christian Franke <christian.fra...@t-online.de>
---
newlib/libc/include/sys/sched.h | 4 ++++
winsup/cygwin/release/3.6.0 | 10 ++++++----
winsup/cygwin/sched.cc | 9 +++++++--
3 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/newlib/libc/include/sys/sched.h b/newlib/libc/include/sys/sched.h
index 4adb6e2d6..c96355c24 100644
--- a/newlib/libc/include/sys/sched.h
+++ b/newlib/libc/include/sys/sched.h
@@ -42,6 +42,10 @@ extern "C" {
#define SCHED_SPORADIC 4
#endif
+#if __GNU_VISIBLE
+#define SCHED_IDLE 5
+#endif
+
/* Scheduling Parameters */
/* Open Group Specifications Issue 6 */
diff --git a/winsup/cygwin/release/3.6.0 b/winsup/cygwin/release/3.6.0
index 9e924dabb..8ca91f0c9 100644
--- a/winsup/cygwin/release/3.6.0
+++ b/winsup/cygwin/release/3.6.0
@@ -54,9 +54,11 @@ What changed:
to POSIX and Linux (glibc >= 2.2.4) behavior.
- sched_setscheduler(2) now emulates changes between SCHED_OTHER,
- SCHED_FIFO and SCHED_RR. If SCHED_OTHER is selected, the Windows
- priority is set according to the nice value. If SCHED_FIFO or
- SCHED_RR is selected, the nice value is preserved and the Windows
- priority is set according to the realtime priority.
+ SCHED_IDLE, SCHED_FIFO and SCHED_RR. If SCHED_OTHER is selected, the
+ Windows priority is set according to the nice value. If SCHED_IDLE is
+ selected, the nice value is preserved and the Windows priority is set
+ to IDLE_PRIORITY_CLASS. If SCHED_FIFO or SCHED_RR is selected, the
+ nice value is preserved and the Windows priority is set according to
+ the realtime priority.
Note: Windows does not offer alternative scheduling policies so
this could only emulate API behavior.
diff --git a/winsup/cygwin/sched.cc b/winsup/cygwin/sched.cc
index c48c433d7..8b4e7efc4 100644
--- a/winsup/cygwin/sched.cc
+++ b/winsup/cygwin/sched.cc
@@ -34,6 +34,7 @@ sched_get_priority_max (int policy)
switch (policy)
{
case SCHED_OTHER:
+ case SCHED_IDLE:
return 0;
case SCHED_FIFO:
case SCHED_RR:
@@ -50,6 +51,7 @@ sched_get_priority_min (int policy)
switch (policy)
{
case SCHED_OTHER:
+ case SCHED_IDLE:
return 0;
case SCHED_FIFO:
case SCHED_RR:
@@ -93,7 +95,7 @@ sched_getparam (pid_t pid, struct sched_param *param)
return -1;
}
- if (p->sched_policy == SCHED_OTHER)
+ if (p->sched_policy == SCHED_OTHER || p->sched_policy == SCHED_IDLE)
{
/* No realtime policy. */
param->sched_priority = 0;
@@ -235,6 +237,9 @@ sched_setparam_pinfo (pinfo & p, const struct sched_param
*param)
if (p->sched_policy == SCHED_OTHER && pri == 0)
/* No realtime policy, reapply the nice value. */
pclass = nice_to_winprio (p->nice);
+ else if (p->sched_policy == SCHED_IDLE && pri == 0)
+ /* Idle policy, ignore the nice value. */
+ pclass = IDLE_PRIORITY_CLASS;
else if (1 <= pri && pri <= 6)
pclass = IDLE_PRIORITY_CLASS;
else if (pri <= 12)
@@ -417,7 +422,7 @@ sched_setscheduler (pid_t pid, int policy,
const struct sched_param *param)
{
if (!(pid >= 0 && param &&
- ((policy == SCHED_OTHER && param->sched_priority == 0) ||
+ (((policy == SCHED_OTHER || policy == SCHED_IDLE) &&
param->sched_priority == 0) ||
((policy == SCHED_FIFO || policy == SCHED_RR) &&
valid_sched_parameters(param)))))
{
set_errno (EINVAL);
--
2.45.1
