Messages in this thread | | | From | Kirill Tkhai <> | Subject | Re:[PATCH 1/4] sched/rt: Sum number of all children tasks in hierarhy at rt_nr_running | Date | Wed, 19 Mar 2014 15:05:11 +0400 |
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> On 03/18/2014 05:14 PM, Kirill Tkhai wrote: > >> 18.03.2014, 15:08, "Preeti Murthy" <preeti.lkml@gmail.com>: >> >>> On Sat, Mar 15, 2014 at 3:44 AM, Kirill Tkhai <tkhai@yandex.ru> wrote: >>> >>>> {inc,dec}_rt_tasks used to count entities which are directly queued >>>> on rt_rq. If an entity was not a task (i.e., it is some queue), its >>>> children were not counted. >>> >>> Its always the case that a task is queued right, never a sched entity? >> >> With patch applied, when sched entity is group queue, we add number of >> its child tasks instead of "1". >> >>> When a task is queued, the nr_running of every rt_rq in the hierarchy >>> of sched entities which are parents of this task is incremented by 1. >> >> Only if they had not had a queued task before. >> >>> Similar is with dequeue of a sched_entity. If the sched_entity has >>> just 1 task on it, then its dequeued from its parent queue and its number >>> decremented for every rq in the hierarchy. But you would >>> never dequeue a sched_entity if it has more than 1 task in it. The >>> granularity of enqueue and dequeue of sched_entities is one task >>> at a time. You can extend this to enqueue and dequeue of a sched_entity >>> only if it has just one task in its queue. >> >> We do not queue entites, which are empty. In __enqueue_rt_entity(): >> >> if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running)) >> return; >> >> Where do you see a collision? Please explain, if so. > > Ok I went through the patchset more closely and I understand it better > now. So this patchset targets the throttled rt runqueues specifically. I > am sorry I missed this focal point. So this patch looks good to me. > > Reviewed-by: Preeti U Murthy <preeti@linux.vnet.ibm.com>
Thanks, Preeti!
>>> Regards >>> Preeti U Murthy >>> >>>> There is no problem here, but now we want to count number of all tasks >>>> which are actually queued under the rt_rq in all the hierarhy (except >>>> throttled rt queues). >>>> >>>> Empty queues are not able to be queued and all of the places, which >>>> use rt_nr_running, just compare it with zero, so we do not break >>>> anything here. >>>> >>>> Signed-off-by: Kirill Tkhai <tkhai@yandex.ru> >>>> CC: Peter Zijlstra <peterz@infradead.org> >>>> CC: Ingo Molnar <mingo@kernel.org> >>>> --- >>>> kernel/sched/rt.c | 15 +++++++++++++-- >>>> 1 file changed, 13 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c >>>> index d8cdf16..e4def13 100644 >>>> --- a/kernel/sched/rt.c >>>> +++ b/kernel/sched/rt.c >>>> @@ -1045,12 +1045,23 @@ void dec_rt_group(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) {} >>>> #endif /* CONFIG_RT_GROUP_SCHED */ >>>> >>>> static inline >>>> +unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se) >>>> +{ >>>> + struct rt_rq *group_rq = group_rt_rq(rt_se); >>>> + >>>> + if (group_rq) >>>> + return group_rq->rt_nr_running; >>>> + else >>>> + return 1; >>>> +} >>>> + >>>> +static inline >>>> void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) >>>> { >>>> int prio = rt_se_prio(rt_se); >>>> >>>> WARN_ON(!rt_prio(prio)); >>>> - rt_rq->rt_nr_running++; >>>> + rt_rq->rt_nr_running += rt_se_nr_running(rt_se); >>>> >>>> inc_rt_prio(rt_rq, prio); >>>> inc_rt_migration(rt_se, rt_rq); >>>> @@ -1062,7 +1073,7 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) >>>> { >>>> WARN_ON(!rt_prio(rt_se_prio(rt_se))); >>>> WARN_ON(!rt_rq->rt_nr_running); >>>> - rt_rq->rt_nr_running--; >>>> + rt_rq->rt_nr_running -= rt_se_nr_running(rt_se); >>>> >>>> dec_rt_prio(rt_rq, rt_se_prio(rt_se)); >>>> dec_rt_migration(rt_se, rt_rq); >>>> >>>> -- >>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>>> the body of a message to majordomo@vger.kernel.org >>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>> Please read the FAQ at http://www.tux.org/lkml/
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