sched: Add sched_avg::utilization_avg_contrib

Add new statistics which reflect the average time a task is running on the CPU
and the sum of these running time of the tasks on a runqueue. The latter is
named utilization_load_avg.

This patch is based on the usage metric that was proposed in the 1st
versions of the per-entity load tracking patchset by Paul Turner
<pjt@google.com> but that has be removed afterwards. This version differs from
the original one in the sense that it's not linked to task_group.

The rq's utilization_load_avg will be used to check if a rq is overloaded or
not instead of trying to compute how many tasks a group of CPUs can handle.

Rename runnable_avg_period into avg_period as it is now used with both
runnable_avg_sum and running_avg_sum.

Add some descriptions of the variables to explain their differences.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Paul Turner <pjt@google.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Ben Segall <bsegall@google.com>
Cc: Morten.Rasmussen@arm.com
Cc: Paul Turner <pjt@google.com>
Cc: dietmar.eggemann@arm.com
Cc: efault@gmx.de
Cc: kamalesh@linux.vnet.ibm.com
Cc: linaro-kernel@lists.linaro.org
Cc: nicolas.pitre@linaro.org
Cc: preeti@linux.vnet.ibm.com
Cc: riel@redhat.com
Link: http://lkml.kernel.org/r/1425052454-25797-2-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 17 insertions, 4 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6d77432e14ff..fdca05c5f812 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1115,15 +1115,28 @@ struct load_weight {
 };
 
 struct sched_avg {
+        u64 last_runnable_update;
+        s64 decay_count;
+        /*
+         * utilization_avg_contrib describes the amount of time that a
+         * sched_entity is running on a CPU. It is based on running_avg_sum
+         * and is scaled in the range [0..SCHED_LOAD_SCALE].
+         * load_avg_contrib described the amount of time that a sched_entity
+         * is runnable on a rq. It is based on both runnable_avg_sum and the
+         * weight of the task.
+         */
+        unsigned long load_avg_contrib, utilization_avg_contrib;
         /*
          * These sums represent an infinite geometric series and so are bound
          * above by 1024/(1-y).  Thus we only need a u32 to store them for all
          * choices of y < 1-2^(-32)*1024.
+         * running_avg_sum reflects the time that the sched_entity is
+         * effectively running on the CPU.
+         * runnable_avg_sum represents the amount of time a sched_entity is on
+         * a runqueue which includes the running time that is monitored by
+         * running_avg_sum.
          */
-        u32 runnable_avg_sum, runnable_avg_period;
-        u64 last_runnable_update;
-        s64 decay_count;
-        unsigned long load_avg_contrib;
+        u32 runnable_avg_sum, avg_period, running_avg_sum;
 };
 
 #ifdef CONFIG_SCHEDSTATS