kernel_samsung_a53x/kernel/sched
Cyril Hrubis ae1abca9a3 sched/rt: Fix sysctl_sched_rr_timeslice intial value
commit c7fcb99877f9f542c918509b2801065adcaf46fa upstream.

There is a 10% rounding error in the intial value of the
sysctl_sched_rr_timeslice with CONFIG_HZ_300=y.

This was found with LTP test sched_rr_get_interval01:

sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90
sched_rr_get_interval01.c:57: TPASS: sched_rr_get_interval() passed
sched_rr_get_interval01.c:64: TPASS: Time quantum 0s 99999990ns
sched_rr_get_interval01.c:72: TFAIL: /proc/sys/kernel/sched_rr_timeslice_ms != 100 got 90

What this test does is to compare the return value from the
sched_rr_get_interval() and the sched_rr_timeslice_ms sysctl file and
fails if they do not match.

The problem it found is the intial sysctl file value which was computed as:

static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC / HZ) * RR_TIMESLICE;

which works fine as long as MSEC_PER_SEC is multiple of HZ, however it
introduces 10% rounding error for CONFIG_HZ_300:

(MSEC_PER_SEC / HZ) * (100 * HZ / 1000)

(1000 / 300) * (100 * 300 / 1000)

3 * 30 = 90

This can be easily fixed by reversing the order of the multiplication
and division. After this fix we get:

(MSEC_PER_SEC * (100 * HZ / 1000)) / HZ

(1000 * (100 * 300 / 1000)) / 300

(1000 * 30) / 300 = 100

Fixes: 975e155ed873 ("sched/rt: Show the 'sched_rr_timeslice' SCHED_RR timeslice tuning knob in milliseconds")
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Tested-by: Petr Vorel <pvorel@suse.cz>
Link: https://lore.kernel.org/r/20230802151906.25258-2-chrubis@suse.cz
[ pvorel: rebased for 5.15, 5.10 ]
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-11-18 22:25:32 +01:00
..
ems Revert "kernel: ems/ego: Allow CPU frequency changes to be amended before they're set" 2024-11-18 07:48:15 +01:00
autogroup.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
autogroup.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
clock.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
completion.c sched/completion: Expose wait_for_common*() to drivers 2024-11-17 17:45:08 +01:00
core.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpuacct.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpudeadline.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpudeadline.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpufreq.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpufreq_schedutil.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpupri.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cpupri.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
cputime.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
deadline.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
debug.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
fair.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
features.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
idle.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
isolation.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
loadavg.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
Makefile Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
membarrier.c sched/membarrier: reduce the ability to hammer on sys_membarrier 2024-11-18 12:13:39 +01:00
pelt.c kernel: sched: Provide more PELT half-life options 2024-11-17 17:41:17 +01:00
pelt.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
psi.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
rt.c sched/rt: Fix sysctl_sched_rr_timeslice intial value 2024-11-18 22:25:32 +01:00
sched-pelt.h kernel: sched: Provide more PELT half-life options 2024-11-17 17:41:17 +01:00
sched.h sched/uclamp: Fix incorrect uclamp.latency_sensitive setting 2024-11-17 17:38:14 +01:00
sec_mpam.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sec_mpam_cpbm.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sec_mpam_sysfs.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
sec_mpam_sysfs.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
smp.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stats.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stats.h Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
stop_task.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
swait.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
topology.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
wait.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00
wait_bit.c Import A536BXXU9EXDC 2024-06-15 16:02:09 -03:00