[RFCv5 PATCH 20/46] sched: Relocated get_cpu_usage() and change return type

Morten Rasmussen
2015-07-07T18:24:35Z

Move get_cpu_usage() to an earlier position in fair.c and change return
type to unsigned long as negative usage doesn't make much sense. All
other load and capacity related functions use unsigned long including
the caller of get_cpu_usage().

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
---
kernel/sched/fair.c | 78 ++++++++++++++++++++++++++---------------------------
1 file changed, 39 insertions(+), 39 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 70f81fc..78d3081 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4802,6 +4802,45 @@ static unsigned long capacity_curr_of(int cpu)
>> SCHED_CAPACITY_SHIFT;
}

+/*
+ * get_cpu_usage 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
+ * compare the usage with the capacity of the CPU that is available for CFS
+ * task (ie 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..capacity_orig] where capacity_orig is the cpu_capacity available at the
+ * highest frequency (arch_scale_freq_capacity()). The usage of a CPU converges
+ * towards a sum equal to or less than the current capacity (capacity_curr <=
+ * capacity_orig) of the CPU because it is the running time on this CPU scaled
+ * by capacity_curr. Nevertheless, cfs.utilization_load_avg can be higher than
+ * capacity_curr or even higher than capacity_orig because of unfortunate
+ * rounding in avg_period and running_load_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 usage stays into the range
+ * [0..capacity_orig] 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. We allow usage to overshoot
+ * capacity_curr (but not capacity_orig) as it useful for predicting the
+ * capacity required after task migrations (scheduler-driven DVFS).
+ */
+
+static unsigned long get_cpu_usage(int cpu)
+{
+ int sum;
+ unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg;
+ unsigned long blocked = cpu_rq(cpu)->cfs.utilization_blocked_avg;
+ unsigned long capacity_orig = capacity_orig_of(cpu);
+
+ sum = usage + blocked;
+
+ if (sum >= capacity_orig)
+ return capacity_orig;
+
+ return sum;
+}
+
static inline bool energy_aware(void)
{
return sched_feat(ENERGY_AWARE);
@@ -5055,45 +5094,6 @@ static int select_idle_sibling(struct task_struct *p, int target)
}

/*
- * get_cpu_usage 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
- * compare the usage with the capacity of the CPU that is available for CFS
- * task (ie 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..capacity_orig] where capacity_orig is the cpu_capacity available at the
- * highest frequency (arch_scale_freq_capacity()). The usage of a CPU converges
- * towards a sum equal to or less than the current capacity (capacity_curr <=
- * capacity_orig) of the CPU because it is the running time on this CPU scaled
- * by capacity_curr. Nevertheless, cfs.utilization_load_avg can be higher than
- * capacity_curr or even higher than capacity_orig because of unfortunate
- * rounding in avg_period and running_load_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 usage stays into the range
- * [0..capacity_orig] 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. We allow usage to overshoot
- * capacity_curr (but not capacity_orig) as it useful for predicting the
- * capacity required after task migrations (scheduler-driven DVFS).
- */
-
-static int get_cpu_usage(int cpu)
-{
- int sum;
- unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg;
- unsigned long blocked = cpu_rq(cpu)->cfs.utilization_blocked_avg;
- unsigned long capacity_orig = capacity_orig_of(cpu);
-
- sum = usage + blocked;
-
- if (sum >= capacity_orig)
- return capacity_orig;
-
- return sum;
-}
-
-/*
* select_task_rq_fair: Select target runqueue for the waking task in domains
* that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
* SD_BALANCE_FORK, or SD_BALANCE_EXEC.
--
1.9.1