diff options
author | Vincent Guittot <vincent.guittot@linaro.org> | 2014-10-24 10:51:48 +0200 |
---|---|---|
committer | Vincent Guittot <vincent.guittot@linaro.org> | 2014-10-31 09:42:22 +0100 |
commit | 3f71cdb35b2a10e2fa01617e3f1517ce3d6ee259 (patch) | |
tree | a3c0eedf25ba5f64708ad31e30f6e2de03edc9be | |
parent | e4aed81aaaa78eb029924f0fc3774b7ac10476c4 (diff) |
sched: make scale_rt invariant with frequencysched-capacity-v8-wipsched-capacity-v8
The average running time of RT tasks is used to estimate the remaining compute
capacity for CFS tasks. This remaining capacity is the original capacity scaled
down by a factor (aka scale_rt_capacity). This estimation of available capacity
must also be invariant with frequency scaling.
A frequency scaling factor is applied on the running time of the RT tasks for
computing scale_rt_capacity.
In sched_rt_avg_update, we scale the RT execution time like below:
rq->rt_avg += rt_delta * arch_scale_freq_capacity() >> SCHED_CAPACITY_SHIFT
Then, scale_rt_capacity can be summarized by:
scale_rt_capacity = SCHED_CAPACITY_SCALE -
((rq->rt_avg << SCHED_CAPACITY_SHIFT) / period)
We can optimize by removing right and left shift in the computation of rq->rt_avg
and scale_rt_capacity
The call to arch_scale_frequency_capacity in the rt scheduling path might be
a concern for RT folks because I'm not sure whether we can rely on
arch_scale_freq_capacity to be short and efficient ?
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
-rw-r--r-- | kernel/sched/fair.c | 17 | ||||
-rw-r--r-- | kernel/sched/sched.h | 4 |
2 files changed, 8 insertions, 13 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 31c3ec2c0a42..02e8f7f3853a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5817,7 +5817,7 @@ unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu) static unsigned long scale_rt_capacity(int cpu) { struct rq *rq = cpu_rq(cpu); - u64 total, available, age_stamp, avg; + u64 total, used, age_stamp, avg; s64 delta; /* @@ -5833,19 +5833,12 @@ static unsigned long scale_rt_capacity(int cpu) total = sched_avg_period() + delta; - if (unlikely(total < avg)) { - /* Ensures that capacity won't end up being negative */ - available = 0; - } else { - available = total - avg; - } + used = div_u64(avg, total); - if (unlikely((s64)total < SCHED_CAPACITY_SCALE)) - total = SCHED_CAPACITY_SCALE; + if (likely(used < SCHED_CAPACITY_SCALE)) + return SCHED_CAPACITY_SCALE - used; - total >>= SCHED_CAPACITY_SHIFT; - - return div_u64(available, total); + return 1; } static void update_cpu_capacity(struct sched_domain *sd, int cpu) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 79639814b440..8fd30c1e7036 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1313,9 +1313,11 @@ static inline int hrtick_enabled(struct rq *rq) #ifdef CONFIG_SMP extern void sched_avg_update(struct rq *rq); +extern unsigned long arch_scale_freq_capacity(struct sched_domain *sd, int cpu); + static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta) { - rq->rt_avg += rt_delta; + rq->rt_avg += rt_delta * arch_scale_freq_capacity(NULL, cpu_of(rq)); sched_avg_update(rq); } #else |