On Thu, Jan 15, 2015 at 11:09:24AM +0100, Vincent Guittot wrote:
From: Morten Rasmussen morten.rasmussen@arm.com
Apply frequency scale-invariance correction factor to usage tracking. Each segment of the running_load_avg geometric series is now scaled by the current frequency so the utilization_avg_contrib of each entity will be invariant with frequency scaling.
As a result, utilization_load_avg which is the sum of utilization_avg_contrib, becomes invariant too. So the usage level that is returned by get_cpu_usage, stays relative to the max frequency as the cpu_capacity which is is compared against.
Then, we want the keep the load tracking values in a 32bits type, which implies that the max value of {runnable|running}_avg_sum must be lower than 2^32/88761=48388 (88761 is the max weigth 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: Paul Turner pjt@google.com cc: Ben Segall bsegall@google.com
Signed-off-by: Morten Rasmussen morten.rasmussen@arm.com Signed-off-by: Vincent Guittot vincent.guittot@linaro.org
kernel/sched/fair.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a96affd..a5039da 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -2266,6 +2266,8 @@ static u32 __compute_runnable_contrib(u64 n) return contrib + runnable_avg_yN_sum[n]; } +unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu);
There is no actual function definition in this patch; this would hinder linking, no?
if (running)
sa->running_avg_sum += delta_w * scale_freq>> SCHED_CAPACITY_SHIFT;
if (running)
sa->running_avg_sum += runnable_contrib * scale_freq>> SCHED_CAPACITY_SHIFT;
if (running)
sa->running_avg_sum += delta * scale_freq>> SCHED_CAPACITY_SHIFT;
If you're going to respin; please but {} around that.