Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 12 Oct 2016 17:45:59 +0200 | Subject | Re: [PATCH 5/7 v4] sched: propagate asynchrous detach |
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On 12 October 2016 at 17:03, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > On 26/09/16 13:19, Vincent Guittot wrote: >> A task can be asynchronously detached from cfs_rq when migrating >> between CPUs. The load of the migrated task is then removed from >> source cfs_rq during its next update. We use this event to set propagation >> flag. >> >> During the load balance, we take advanatge of the update of blocked load >> to we propagate any pending changes. > > IMHO, it would be a good idea to mention that '2/7 sched: fix > hierarchical order in rq->leaf_cfs_rq_list' is a hard requirement for > this to work. The functionality relies on the order of cfs_rq's (top to > root) in the rq->leaf_cfs_rq_list list.
yes. i will add a comment
> >> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> >> --- >> kernel/sched/fair.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 8ba500f..bd3b6b9 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -3221,6 +3221,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq) >> sub_positive(&sa->load_avg, r); >> sub_positive(&sa->load_sum, r * LOAD_AVG_MAX); >> removed_load = 1; >> + set_tg_cfs_propagate(cfs_rq); >> } >> >> if (atomic_long_read(&cfs_rq->removed_util_avg)) { >> @@ -3228,6 +3229,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq) >> sub_positive(&sa->util_avg, r); >> sub_positive(&sa->util_sum, r * LOAD_AVG_MAX); >> removed_util = 1; >> + set_tg_cfs_propagate(cfs_rq); >> } >> >> decayed = __update_load_avg(now, cpu_of(rq_of(cfs_rq)), sa, >> @@ -6607,6 +6609,10 @@ static void update_blocked_averages(int cpu) >> >> if (update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq, true)) >> update_tg_load_avg(cfs_rq, 0); >> + >> + /* Propagate pending load changes to the parent */ >> + if (cfs_rq->tg->se[cpu]) >> + update_load_avg(cfs_rq->tg->se[cpu], 0); > > In my test (1 task (run/period: 8ms/16ms) in tg_root->tg_x->tg_y->*tg_z* > and oscillating between cpu1 and cpu2) the cfs_rq related signals are > nicely going down to 0 after the task has left the cpu but it doesn't > seem to be the case for the corresponding se (cfs_rq->tg->se[cpu])?
strange because such use case is part of the functional tests that I run and it was working fine according to last test that I did
> > It should actually work correctly because of the > update_tg_cfs_util/load() calls in update_load_avg(cfs_rq->tg->se[cpu], > 0)->propagate_entity_load_avg()
Furthermore, the update of the parent cfs_rq tg_x->cfs_rq[cpu] uses the delta between previous and new value for the child tg_y->se[cpu]. So it means that if tg_x->cfs_rq[cpu]->avg.load_avg goes down to 0, tg_y->se[cpu]->avg.load_avg has at least changed and most probably goes down to 0 too
Can't it be a misplaced trace point ?
> > [...]
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