Messages in this thread Patch in this message | | | From | Paul Turner <> | Date | Fri, 26 Jul 2013 14:24:50 -0700 | Subject | Re: PROBLEM: Persistent unfair sharing of a processor by auto groups in 3.11-rc2 (has twice regressed) |
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On Fri, Jul 26, 2013 at 2:03 PM, Peter Zijlstra <peterz@infradead.org> wrote: > > > 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()
Yes, I agree: placing it directly in entity_tick() would be better.
[ In f269ae046 the calls to update_cfs_rq_blocked_load() were amortized and the separate update in {en,de}queue_entity_load_avg() were removed. ]
> > > > --- > 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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