Messages in this thread | | | Date | Wed, 16 Aug 2017 09:38:11 +0900 | From | Byungchul Park <> | Subject | Re: [PATCH v6 1/2] sched/deadline: Add support for SD_PREFER_SIBLING on find_later_rq() |
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On Tue, Aug 15, 2017 at 11:19:40AM -0400, Steven Rostedt wrote: > > @@ -1385,6 +1407,17 @@ static int find_later_rq(struct task_struct *task) > > * already under consideration through later_mask. > > */ > > if (best_cpu < nr_cpu_ids) { > > + /* > > + * If current domain is SD_PREFER_SIBLING > > + * flaged, we have to get more chances to > > + * check other siblings. > > + */ > > + if (sd->flags & SD_PREFER_SIBLING) { > > + prefer = sd; > > Is this how the SD_PREFER_SIBLING works? According to this, the > preferred sd is the next sd in for_each_domain(). Not to mention, the > prefer variable stays set if the next domain has no available CPUs. Is > that what we want?
Maybe I don't understand what you want to say. The variable, prefer, is used to pick up the smallest sched domain among SD_PREFER_SIBLING domains, if more than one SD_PREFER_SIBLING domain exist in the visit.
The prefer variable alway points to the previous SD_PREFER_SIBLING domain. And that must stay set to be used as a fallback choise if the next domain has no available CPUs.
Could you explain what I mis-understand?
Thanks, Byungchul
> -- Steve > > > > + if (fallback_cpu == -1) > > + fallback_cpu = best_cpu; > > + continue; > > + } > > rcu_read_unlock(); > > return best_cpu; > > } > > @@ -1393,6 +1426,13 @@ static int find_later_rq(struct task_struct *task) > > rcu_read_unlock(); > > > > /* > > + * If fallback_cpu is valid, all our guesses failed *except* for > > + * SD_PREFER_SIBLING domain. Now, we can return the fallback cpu. > > + */ > > + if (fallback_cpu != -1) > > + return fallback_cpu; > > + > > + /* > > * At this point, all our guesses failed, we just return > > * 'something', and let the caller sort the things out. > > */
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