With scale-invariant usage tracking get_cpu_usage() should never return a usage above the current compute capacity of the cpu (capacity_curr). The scaling of the utilization tracking contributions should generally cause the cpu utilization to saturate at capacity_curr, but it may temporarily exceed this value in certain situations. This patch changes the cap from capacity_orig to capacity_curr.
cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 071310a..872ae0e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4582,13 +4582,13 @@ static unsigned long capacity_curr_of(int cpu) * cpu_capacity). * cfs.utilization_load_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 - * [0..SCHED_LOAD_SCALE]. The usage of a CPU can't be higher than the full + * [0..capacity_curr]. The usage of a CPU can't be higher than the current * capacity of the CPU because it's about the running time on this CPU. - * Nevertheless, cfs.utilization_load_avg can be higher than SCHED_LOAD_SCALE + * Nevertheless, cfs.utilization_load_avg can be higher than capacity_curr * because of unfortunate rounding in avg_period and running_load_avg or just * after migrating tasks until the average stabilizes with the new running * time. So we need to check that the usage stays into the range - * [0..cpu_capacity_orig] and cap if necessary. + * [0..cpu_capacity_curr] and cap if necessary. * Without capping the usage, a group could be seen as overloaded (CPU0 usage * at 121% + CPU1 usage at 80%) whereas CPU1 has 20% of available capacity/ */ @@ -4596,9 +4596,10 @@ static int get_cpu_usage(int cpu) { unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg; unsigned long blocked = cpu_rq(cpu)->cfs.utilization_blocked_avg; + unsigned long capacity_curr = capacity_curr_of(cpu); - if (usage + blocked >= SCHED_LOAD_SCALE) - return capacity_orig_of(cpu); + if (usage + blocked >= capacity_curr) + return capacity_curr; return usage + blocked; } -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
