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sched/fair: Get rid of scaling utilization by capacity_orig 

Utilization is currently scaled by capacity_orig, but since we now have
frequency and cpu invariant cfs_rq.avg.util_avg, frequency and cpu scaling
now happens as part of the utilization tracking itself.
So cfs_rq.avg.util_avg should no longer be scaled in cpu_util().

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <Juri.Lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steve Muckle <steve.muckle@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: daniel.lezcano@linaro.org <daniel.lezcano@linaro.org>
Cc: mturquette@baylibre.com <mturquette@baylibre.com>
Cc: pang.xunlei@zte.com.cn <pang.xunlei@zte.com.cn>
Cc: rjw@rjwysocki.net <rjw@rjwysocki.net>
Cc: sgurrappadi@nvidia.com <sgurrappadi@nvidia.com>
Cc: vincent.guittot@linaro.org <vincent.guittot@linaro.org>
Cc: yuyang.du@intel.com <yuyang.du@intel.com>
Link: http://lkml.kernel.org/r/55EDAF43.30500@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Dietmar Eggemann 2015-08-14 17:23:13 +01:00 committed by Ingo Molnar
parent 9e91d61d9b
commit 231678b768
1 changed files with 22 additions and 16 deletions
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38
kernel/sched/fair.c
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@ -4862,33 +4862,39 @@ next:
done: done:
return target; return target;
} }
/* /*
* cpu_util returns the amount of capacity of a CPU that is used by CFS * cpu_util returns the amount of capacity of a CPU that is used by CFS
* tasks. The unit of the return value must be the one of capacity so we can * tasks. The unit of the return value must be the one of capacity so we can
* compare the utilization with the capacity of the CPU that is available for * compare the utilization with the capacity of the CPU that is available for
* CFS task (ie cpu_capacity). * CFS task (ie cpu_capacity).
* cfs.avg.util_avg is the sum of running time of runnable tasks on a *
* CPU. It represents the amount of utilization of a CPU in the range * cfs_rq.avg.util_avg is the sum of running time of runnable tasks plus the
* [0..SCHED_LOAD_SCALE]. The utilization of a CPU can't be higher than the * recent utilization of currently non-runnable tasks on a CPU. It represents
* full capacity of the CPU because it's about the running time on this CPU. * the amount of utilization of a CPU in the range [0..capacity_orig] where
* Nevertheless, cfs.avg.util_avg can be higher than SCHED_LOAD_SCALE * capacity_orig is the cpu_capacity available at the highest frequency
* because of unfortunate rounding in util_avg or just * (arch_scale_freq_capacity()).
* after migrating tasks until the average stabilizes with the new running * The utilization of a CPU converges towards a sum equal to or less than the
* time. So we need to check that the utilization stays into the range * current capacity (capacity_curr <= capacity_orig) of the CPU because it is
* [0..cpu_capacity_orig] and cap if necessary. * the running time on this CPU scaled by capacity_curr.
* Without capping the utilization, a group could be seen as overloaded (CPU0 *
* utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of * Nevertheless, cfs_rq.avg.util_avg can be higher than capacity_curr or even
* available capacity. * higher than capacity_orig because of unfortunate rounding in
* cfs.avg.util_avg or just after migrating tasks and new task wakeups until
* the average stabilizes with the new running time. We need to check that the
* utilization stays within the range of [0..capacity_orig] and cap it if
* necessary. Without utilization capping, a group could be seen as overloaded
* (CPU0 utilization at 121% + CPU1 utilization at 80%) whereas CPU1 has 20% of
* available capacity. We allow utilization to overshoot capacity_curr (but not
* capacity_orig) as it useful for predicting the capacity required after task
* migrations (scheduler-driven DVFS).
*/ */
static int cpu_util(int cpu) static int cpu_util(int cpu)
{ {
unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg; unsigned long util = cpu_rq(cpu)->cfs.avg.util_avg;
unsigned long capacity = capacity_orig_of(cpu); unsigned long capacity = capacity_orig_of(cpu);
if (util >= SCHED_LOAD_SCALE) return (util >= capacity) ? capacity : util;
return capacity;
return (util * capacity) >> SCHED_LOAD_SHIFT;
} }
/* /*