Messages in this thread | | | From | Amit Kucheria <> | Date | Tue, 19 Nov 2019 16:22:12 +0530 | Subject | Re: [Patch v5 6/6] sched/fair: Enable tuning of decay period |
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On Wed, Nov 6, 2019 at 12:20 AM Thara Gopinath <thara.gopinath@linaro.org> wrote: > > Thermal pressure follows pelt signas which means the > decay period for thermal pressure is the default pelt > decay period. Depending on soc charecteristics 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: Thara Gopinath <thara.gopinath@linaro.org> > --- > > v4->v5: > - Changed _coeff to _shift as per review comments on the list. > > Documentation/admin-guide/kernel-parameters.txt | 5 +++++ > kernel/sched/fair.c | 25 +++++++++++++++++++++++-- > 2 files changed, 28 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index c82f87c..0b8f55e 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4281,6 +4281,11 @@ > incurs a small amount of overhead in the scheduler > but is useful for debugging and performance tuning. > > + sched_thermal_decay_shift= > + [KNL, SMP] Set decay shift for thermal pressure signal. > + Format: integer betweer 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. > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 5f6c371..61a020b 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -91,6 +91,18 @@ const_debug unsigned int sysctl_sched_migration_cost = 500000UL; > * and maximum available capacity due to thermal events. > */ > static DEFINE_PER_CPU(unsigned long, thermal_pressure); > +/** > + * 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 > + */ > +static int sched_thermal_decay_shift; > > static void trigger_thermal_pressure_average(struct rq *rq); > > @@ -10435,6 +10447,15 @@ void update_thermal_pressure(int cpu, unsigned long capped_capacity) > delta = arch_scale_cpu_capacity(cpu) - capped_capacity; > per_cpu(thermal_pressure, cpu) = delta; > } > + > +static int __init setup_sched_thermal_decay_shift(char *str) > +{ > + if (kstrtoint(str, 0, &sched_thermal_decay_shift)) > + pr_warn("Unable to set scheduler thermal pressure decay shift parameter\n");
You're reading straight from the cmdline into a kernel variable w/o any bounds checking. Perhaps use clamp or clamp_val to make sure it is between 0 and 10?
> + > + return 1; > +} > +__setup("sched_thermal_decay_shift=", setup_sched_thermal_decay_shift); > #endif > > /** > @@ -10444,8 +10465,8 @@ void update_thermal_pressure(int cpu, unsigned long capped_capacity) > static void trigger_thermal_pressure_average(struct rq *rq) > { > #ifdef CONFIG_SMP > - update_thermal_load_avg(rq_clock_task(rq), rq, > - per_cpu(thermal_pressure, cpu_of(rq))); > + update_thermal_load_avg(rq_clock_task(rq) >> sched_thermal_decay_shift, > + rq, per_cpu(thermal_pressure, cpu_of(rq))); > #endif > } > > -- > 2.1.4 >
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