Messages in this thread Patch in this message | | | Date | Fri, 26 Jul 2013 23:03:17 +0200 | From | Peter Zijlstra <> | Subject | Re: PROBLEM: Persistent unfair sharing of a processor by auto groups in 3.11-rc2 (has twice regressed) |
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OK, so I have the below; however on a second look, Paul, shouldn't that update_cfs_shares() call be in entity_tick(), right after calling update_cfs_rq_blocked_load(). Because placing it in update_cfs_rq_blocked_load() means its now called twice on the enqueue/dequeue paths through:
{en,de}queue_entity() {en,de}queue_entity_load_avg() update_cfs_rq_blocked_load() update_cfs_shares()
--- Subject: sched: Ensure update_cfs_shares() is called for parents of continuously-running tasks From: Max Hailperin <max@gustavus.edu>
We typically update a task_group's shares within the dequeue/enqueue path. However, continuously running tasks sharing a CPU are not subject to these updates as they are only put/picked. Unfortunately, when we reverted f269ae046 (in 17bc14b7), we lost the augmenting periodic update that was supposed to account for this; resulting in a potential loss of fairness.
To fix this, re-introduce the explicit update in update_cfs_rq_blocked_load() [called via entity_tick()].
Cc: stable@kernel.org Reviewed-by: Paul Turner <pjt@google.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> --- kernel/sched/fair.c | 1 + 1 file changed, 1 insertion(+)
--- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -1531,6 +1531,7 @@ static void update_cfs_rq_blocked_load(s } __update_cfs_rq_tg_load_contrib(cfs_rq, force_update); + update_cfs_shares(cfs_rq); } static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
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