Commit 05289b90 authored by Thara Gopinath's avatar Thara Gopinath Committed by Ingo Molnar

sched/fair: Enable tuning of decay period

Thermal pressure follows pelt signals which means the decay period for
thermal pressure is the default pelt decay period. Depending on SoC
characteristics and thermal activity, it might be beneficial to decay
thermal pressure slower, but still in-tune with the pelt signals.  One way
to achieve this is to provide a command line parameter to set a decay
shift parameter to an integer between 0 and 10.
Signed-off-by: default avatarThara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-10-thara.gopinath@linaro.org
parent f12e4f66
......@@ -4392,6 +4392,22 @@
incurs a small amount of overhead in the scheduler
but is useful for debugging and performance tuning.
sched_thermal_decay_shift=
[KNL, SMP] Set a decay shift for scheduler thermal
pressure signal. Thermal pressure signal follows the
default decay period of other scheduler pelt
signals(usually 32 ms but configurable). Setting
sched_thermal_decay_shift will left shift the decay
period for the thermal pressure signal by the shift
value.
i.e. with the default pelt decay period of 32 ms
sched_thermal_decay_shift thermal pressure decay pr
1 64 ms
2 128 ms
and so on.
Format: integer between 0 and 10
Default is 0.
skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
xtime_lock contention on larger systems, and/or RCU lock
contention on all systems with CONFIG_MAXSMP set.
......
......@@ -3595,7 +3595,7 @@ void scheduler_tick(void)
update_rq_clock(rq);
thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq));
update_thermal_load_avg(rq_clock_task(rq), rq, thermal_pressure);
update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure);
curr->sched_class->task_tick(rq, curr, 0);
calc_global_load_tick(rq);
psi_task_tick(rq);
......
......@@ -86,6 +86,19 @@ static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL;
const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
int sched_thermal_decay_shift;
static int __init setup_sched_thermal_decay_shift(char *str)
{
int _shift = 0;
if (kstrtoint(str, 0, &_shift))
pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
sched_thermal_decay_shift = clamp(_shift, 0, 10);
return 1;
}
__setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift);
#ifdef CONFIG_SMP
/*
* For asym packing, by default the lower numbered CPU has higher priority.
......@@ -7760,7 +7773,7 @@ static bool __update_blocked_others(struct rq *rq, bool *done)
decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
update_thermal_load_avg(rq_clock_task(rq), rq, thermal_pressure) |
update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure) |
update_irq_load_avg(rq, 0);
if (others_have_blocked(rq))
......
......@@ -1127,6 +1127,24 @@ static inline u64 rq_clock_task(struct rq *rq)
return rq->clock_task;
}
/**
* By default the decay is the default pelt decay period.
* The decay shift can change the decay period in
* multiples of 32.
* Decay shift Decay period(ms)
* 0 32
* 1 64
* 2 128
* 3 256
* 4 512
*/
extern int sched_thermal_decay_shift;
static inline u64 rq_clock_thermal(struct rq *rq)
{
return rq_clock_task(rq) >> sched_thermal_decay_shift;
}
static inline void rq_clock_skip_update(struct rq *rq)
{
lockdep_assert_held(&rq->lock);
......
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