On 01/09/17 14:21, Peter Zijlstra wrote:

The load balancer uses runnable_load_avg as load indicator. For
!cgroup this is:

runnable_load_avg = \Sum se->avg.load_avg ; where se->on_rq

That is, a direct sum of all runnable tasks on that runqueue. As
opposed to load_avg, which is a sum of all tasks on the runqueue,
which includes a blocked component.

However, in the cgroup case, this comes apart since the group entities
are always runnable, even if most of their constituent entities are
blocked.

Therefore introduce a runnable_weight which for task entities is the
same as the regular weight, but for group entities is a fraction of
the entity weight and represents the runnable part of the group
runqueue.

Then propagate this load through the PELT hierarchy to arrive at an
effective runnable load avgerage -- which we should not confuse with
the canonical runnable load average.

Suggested-by: Tejun Heo <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
---
include/linux/sched.h | 3
kernel/sched/debug.c | 8 ++
kernel/sched/fair.c | 173 ++++++++++++++++++++++++++++++++------------------
kernel/sched/sched.h | 3
4 files changed, 125 insertions(+), 62 deletions(-)

[...]

@@ -2931,31 +2949,45 @@ static long calc_cfs_shares(struct cfs_r

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

-static void update_cfs_shares(struct sched_entity *se)
+/*
+ * Recomputes the group entity based on the current state of its group
+ * runqueue.
+ */
+static void update_cfs_group(struct sched_entity *se)

update_cfs_share(s)() is still mentioned in the function header of update_tg_load_avg() and update_cfs_rq_load_avg().

Should we rename those comments with this patch?

IMHO, the comment for update_tg_load_avg() is still true whereas the one
for update_cfs_rq_load_avg() mentions cfs_rq->avg as
cfs_rq->avg.load_avg (or cfs_rq_load_avg()) and update_cfs_group()
doesn't use it anymore. It's now used in calc_group_runnable() and calc_group_shares() instead.

[...]

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