diff options
author | Dietmar Eggemann <dietmar.eggemann@arm.com> | 2014-11-14 15:09:45 +0000 |
---|---|---|
committer | Robin Randhawa <robin.randhawa@arm.com> | 2015-04-09 12:26:12 +0100 |
commit | e925532d3eacdd0a174e44fb05de3adb25bdb2f0 (patch) | |
tree | 6debdd424172aafb09361764138e564fb9b0de40 | |
parent | 41478595352b48f79d475bc13718acbee88ccb29 (diff) |
sched: Make load tracking frequency scale-invariant
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>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
-rw-r--r-- | kernel/sched/fair.c | 28 |
1 files changed, 16 insertions, 12 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index abfc3685e495..17f571acdb83 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2234,9 +2234,9 @@ 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; @@ -2270,11 +2270,12 @@ 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; @@ -2292,20 +2293,23 @@ 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; |