| Message ID | 1417529192-11579-2-git-send-email-morten.rasmussen@arm.com (mailing list archive) |
|---|---|
| State | RFC, archived |
| Headers | show |
On 2 December 2014 at 15:06, Morten Rasmussen <morten.rasmussen@arm.com> wrote: > From: Dietmar Eggemann <dietmar.eggemann@arm.com> > > Apply frequency scale-invariance correction factor to load tracking. > Each segment of the sched_avg::runnable_avg_sum geometric series is now > scaled by the current frequency so the sched_avg::load_avg_contrib of each > entity will be invariant with frequency scaling. As a result, > cfs_rq::runnable_load_avg which is the sum of sched_avg::load_avg_contrib, > becomes invariant too. So the load level that is returned by > weighted_cpuload, stays relative to the max frequency of the cpu. > > Then, we want the keep the load tracking values in a 32bits type, which > implies that the max value of sched_avg::{runnable|running}_avg_sum must > be lower than 2^32/88761=48388 (88761 is the max weight of a task). As > LOAD_AVG_MAX = 47742, arch_scale_freq_capacity must return a value less > than (48388/47742) << SCHED_CAPACITY_SHIFT = 1037 (SCHED_SCALE_CAPACITY = > 1024). So we define the range to [0..SCHED_SCALE_CAPACITY] in order to > avoid overflow. > > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Peter Zijlstra <peterz@infradead.org> > Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com> > --- > kernel/sched/fair.c | 28 ++++++++++++++++------------ > 1 file changed, 16 insertions(+), 12 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index ee76d52..b41f03d 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -2507,9 +2507,9 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, > int runnable, > int running) > { > - u64 delta, periods; > - u32 runnable_contrib; > - int delta_w, decayed = 0; > + u64 delta, scaled_delta, periods; > + u32 runnable_contrib, scaled_runnable_contrib; > + int delta_w, scaled_delta_w, decayed = 0; > unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); > > delta = now - sa->last_runnable_update; > @@ -2543,11 +2543,12 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, > * period and accrue it. > */ > delta_w = 1024 - delta_w; > + scaled_delta_w = (delta_w * scale_freq) >> SCHED_CAPACITY_SHIFT; > + > if (runnable) > - sa->runnable_avg_sum += delta_w; > + sa->runnable_avg_sum += scaled_delta_w; > if (running) > - sa->running_avg_sum += delta_w * scale_freq > - >> SCHED_CAPACITY_SHIFT; > + sa->running_avg_sum += scaled_delta_w; > sa->avg_period += delta_w; > > delta -= delta_w; > @@ -2565,20 +2566,23 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, > > /* Efficiently calculate \sum (1..n_period) 1024*y^i */ > runnable_contrib = __compute_runnable_contrib(periods); > + scaled_runnable_contrib = (runnable_contrib * scale_freq) > + >> SCHED_CAPACITY_SHIFT; > + > if (runnable) > - sa->runnable_avg_sum += runnable_contrib; > + sa->runnable_avg_sum += scaled_runnable_contrib; > if (running) > - sa->running_avg_sum += runnable_contrib * scale_freq > - >> SCHED_CAPACITY_SHIFT; > + sa->running_avg_sum += scaled_runnable_contrib; > sa->avg_period += runnable_contrib; > } > > /* Remainder of delta accrued against u_0` */ > + scaled_delta = (delta * scale_freq) >> SCHED_CAPACITY_SHIFT; > + > if (runnable) > - sa->runnable_avg_sum += delta; > + sa->runnable_avg_sum += scaled_delta; > if (running) > - sa->running_avg_sum += delta * scale_freq > - >> SCHED_CAPACITY_SHIFT; > + sa->running_avg_sum += scaled_delta; > sa->avg_period += delta; > > return decayed; Acked-by: Vincent Guittot <vincent.guittot@linaro.org> > -- > 1.9.1 > > -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index ee76d52..b41f03d 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2507,9 +2507,9 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, int runnable, int running) { - u64 delta, periods; - u32 runnable_contrib; - int delta_w, decayed = 0; + u64 delta, scaled_delta, periods; + u32 runnable_contrib, scaled_runnable_contrib; + int delta_w, scaled_delta_w, decayed = 0; unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu); delta = now - sa->last_runnable_update; @@ -2543,11 +2543,12 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, * period and accrue it. */ delta_w = 1024 - delta_w; + scaled_delta_w = (delta_w * scale_freq) >> SCHED_CAPACITY_SHIFT; + if (runnable) - sa->runnable_avg_sum += delta_w; + sa->runnable_avg_sum += scaled_delta_w; if (running) - sa->running_avg_sum += delta_w * scale_freq - >> SCHED_CAPACITY_SHIFT; + sa->running_avg_sum += scaled_delta_w; sa->avg_period += delta_w; delta -= delta_w; @@ -2565,20 +2566,23 @@ static __always_inline int __update_entity_runnable_avg(u64 now, int cpu, /* Efficiently calculate \sum (1..n_period) 1024*y^i */ runnable_contrib = __compute_runnable_contrib(periods); + scaled_runnable_contrib = (runnable_contrib * scale_freq) + >> SCHED_CAPACITY_SHIFT; + if (runnable) - sa->runnable_avg_sum += runnable_contrib; + sa->runnable_avg_sum += scaled_runnable_contrib; if (running) - sa->running_avg_sum += runnable_contrib * scale_freq - >> SCHED_CAPACITY_SHIFT; + sa->running_avg_sum += scaled_runnable_contrib; sa->avg_period += runnable_contrib; } /* Remainder of delta accrued against u_0` */ + scaled_delta = (delta * scale_freq) >> SCHED_CAPACITY_SHIFT; + if (runnable) - sa->runnable_avg_sum += delta; + sa->runnable_avg_sum += scaled_delta; if (running) - sa->running_avg_sum += delta * scale_freq - >> SCHED_CAPACITY_SHIFT; + sa->running_avg_sum += scaled_delta; sa->avg_period += delta; return decayed;