Messages in this thread | | | Date | Tue, 12 Jun 2007 09:52:47 +0530 | From | Srivatsa Vaddagiri <> | Subject | Re: [RFC][PATCH 3/6] core changes in CFS |
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On Tue, Jun 12, 2007 at 07:59:22AM +0530, Balbir Singh wrote: > > +#define entity_is_task(se) 1 > > Could you add some comments as to what this means?
sure. Basically this macro tests whether a given schedulable entity is task or not. Other possible schedulable entities could be process, user, container etc. These various entities form a hierarchy with task being at the bottom of the hierarchy.
> Should be it boolean instead (true)
I don't have a good opinion on this. Would it make sparse friendly?
> > + * Enqueue a entity into the rb-tree: > > Enqueue an entity
yes
> > > -static void limit_wait_runtime(struct rq *rq, struct task_struct *p) > > +static void limit_wait_runtime(struct lrq *lrq, struct sched_entity *p) > > p is a general convention for tasks in the code, could we use something > different -- may be "e"?
'se' perhaps as is used elsewhere. I avoided making that change so that people will see less diff o/p in the patch :) I agree though a better name is needed.
> > static s64 div64_s(s64 divident, unsigned long divisor) > > @@ -183,49 +219,51 @@ > > * Update the current task's runtime statistics. Skip current tasks that > > * are not in our scheduling class. > > */ > > -static inline void update_curr(struct rq *rq, u64 now) > > +static inline void update_curr(struct lrq *lrq, u64 now) > > { > > - unsigned long load = rq->lrq.raw_weighted_load; > > + unsigned long load = lrq->raw_weighted_load; > > u64 delta_exec, delta_fair, delta_mine; > > - struct task_struct *curr = rq->curr; > > + struct sched_entity *curr = lrq_curr(lrq); > > How about curr_entity?
I prefer its current name, but will consider your suggestion in next iteration.
> > + struct rq *rq = lrq_rq(lrq); > > + struct task_struct *curtask = rq->curr; > > > > - if (curr->sched_class != &fair_sched_class || curr == rq->idle || !load) > > + if (!curr || curtask == rq->idle || !load) > > Can !curr ever be true? shoudn't we look into the sched_class of the task > that the entity belongs to?
Couple of cases that we need to consider here:
CONFIG_FAIR_GROUP_SCHED disabled:
lrq_curr() essentially returns NULL if currently running task doesnt belong to fair_sched_class, else it returns &rq->curr->se So the check for fair_sched_class is taken care in that function.
CONFIG_FAIR_GROUP_SCHED enabled:
lrq_curr() returns lrq->curr. I introduced ->curr field in lrq to optimize on not having to update lrq's fair_clock (update_curr upon enqueue/dequeue task) if it was not currently "active".
Lets say that there are two groups 'vatsa' and 'guest' with their own lrqs on each cpu. If CPU0 is currently running a task from group 'vatsa', then lrq_vatsa->curr will point to the currently running task, while lrq_guest->curr will be NULL. While the task from 'vatsa' is running, if we were to enqueue/dequeue task from group 'guest', we need not update lrq_guest's fair_clock (as it is not active currently). This optimization in update_curr is made possible by maintaining a 'curr' field in lrq.
Hope this answers your question.
-- Regards, vatsa - 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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