Tijl Coosemans wrote:
Author: tijl
Date: Sun Mar 1 13:12:04 2020
New Revision: 358483
URL: https://svnweb.freebsd.org/changeset/base/358483
Log:
linuxulator: Map scheduler priorities to Linux priorities.
On Linux the valid range of priorities for the SCHED_FIFO and SCHED_RR
scheduling policies is [1,99]. For SCHED_OTHER the single valid priority is
0. On FreeBSD it is [0,31] for all policies. Programs are supposed to
query the valid range using sched_get_priority_(min|max), but of course some
programs assume the Linux values are valid.
This commit adds a tunable compat.linux.map_sched_prio. When enabled
sched_get_priority_(min|max) return the Linux values and sched_setscheduler
and sched_(get|set)param translate between FreeBSD and Linux values.
Because there are more Linux levels than FreeBSD levels, multiple Linux
levels map to a single FreeBSD level, which means pre-emption might not
happen as it does on Linux, so the tunable allows to disable this behaviour.
It is enabled by default because I think it is unlikely that anyone runs
real-time software under Linux emulation on FreeBSD that critically relies
on correct pre-emption.
This fixes FMOD, a commercial sound library used by several games.
PR: 240043
Tested by: Alex S <iwt...@gmail.com>
Reviewed by: dchagin
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D23790
Modified:
head/sys/compat/linux/linux_misc.c
head/sys/compat/linux/linux_misc.h
Modified: head/sys/compat/linux/linux_misc.c
==============================================================================
--- head/sys/compat/linux/linux_misc.c Sun Mar 1 12:34:27 2020
(r358482)
+++ head/sys/compat/linux/linux_misc.c Sun Mar 1 13:12:04 2020
(r358483)
@@ -144,6 +144,11 @@ struct l_pselect6arg {
l_size_t ss_len;
};
+static bool map_sched_prio = true;
+SYSCTL_BOOL(_compat_linux, OID_AUTO, map_sched_prio, CTLFLAG_RDTUN,
+ &map_sched_prio, 0, "Map scheduler priorities to Linux priorities "
+ "(not POSIX compliant)");
I'm seeing the following in the log:
sysctl_warn_reuse: can't re-use a leaf (compat.linux.map_sched_prio)!
Should this be done for both linux and linux32 (when one exists) or made
to install one time only?
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