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authorVincent Guittot <vincent.guittot@linaro.org>2019-01-23 16:26:54 +0100
committerIngo Molnar <mingo@kernel.org>2019-02-04 09:13:21 +0100
commit10a35e6812aa0953f02a956c499d23fe4e68af4a (patch)
tree11c866b0777d735f814a0886e91eb0139f7cc4e4
parent23127296889fe84b0762b191b5d041e8ba6f2599 (diff)
sched/pelt: Skip updating util_est when utilization is higher than CPU's capacity
util_est is mainly meant to be a lower-bound for tasks utilization. That's why task_util_est() returns the actual util_avg when it's higher than the estimated utilization. With new invaraince signal and without any special check on samples collection, if a task is limited because of thermal capping for example, we could end up overestimating its utilization and thus perhaps generating an unwanted frequency spike when the capping is relaxed... and (even worst) it will take some more activations for the estimated utilization to converge back to the actual utilization. Since we cannot easily know if there is idle time in a CPU when a task completes an activation with a utilization higher then the CPU capacity, we skip the sampling when utilization is higher than CPU's capacity. Suggested-by: Patrick Bellasi <patrick.bellasi@arm.com> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Morten.Rasmussen@arm.com Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: bsegall@google.com Cc: dietmar.eggemann@arm.com Cc: pjt@google.com Cc: pkondeti@codeaurora.org Cc: quentin.perret@arm.com Cc: rjw@rjwysocki.net Cc: srinivas.pandruvada@linux.intel.com Cc: thara.gopinath@linaro.org Link: https://lkml.kernel.org/r/1548257214-13745-4-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/fair.c14
-rw-r--r--kernel/sched/sched.h7
2 files changed, 16 insertions, 5 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f41f2eec6186..8c165f0d33b3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3638,6 +3638,7 @@ util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
{
long last_ewma_diff;
struct util_est ue;
+ int cpu;
if (!sched_feat(UTIL_EST))
return;
@@ -3672,6 +3673,14 @@ util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
return;
/*
+ * To avoid overestimation of actual task utilization, skip updates if
+ * we cannot grant there is idle time in this CPU.
+ */
+ cpu = cpu_of(rq_of(cfs_rq));
+ if (task_util(p) > capacity_orig_of(cpu))
+ return;
+
+ /*
* Update Task's estimated utilization
*
* When *p completes an activation we can consolidate another sample
@@ -5542,11 +5551,6 @@ static unsigned long capacity_of(int cpu)
return cpu_rq(cpu)->cpu_capacity;
}
-static unsigned long capacity_orig_of(int cpu)
-{
- return cpu_rq(cpu)->cpu_capacity_orig;
-}
-
static unsigned long cpu_avg_load_per_task(int cpu)
{
struct rq *rq = cpu_rq(cpu);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index fe31bc472f3e..99e2a7772d16 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2230,6 +2230,13 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) {}
# define arch_scale_freq_invariant() false
#endif
+#ifdef CONFIG_SMP
+static inline unsigned long capacity_orig_of(int cpu)
+{
+ return cpu_rq(cpu)->cpu_capacity_orig;
+}
+#endif
+
#ifdef CONFIG_CPU_FREQ_GOV_SCHEDUTIL
/**
* enum schedutil_type - CPU utilization type