On Mon, Jan 19, 2015 at 04:49:40AM +0000, Xunlei Pang wrote: > In find_lowest_rq(), if we can't find a wake_affine cpu from > sched_domain, then we can actually determine a cache hot cpu > instead of simply calling "cpumask_any(lowest_mask)" which > always returns the first cpu in the mask. > > So, we can determine the cache hot cpu during the interation of > sched_domain() in passing.
Steve, I'm not getting this. Why are we using WAKE_AFFINE here? > Signed-off-by: Xunlei Pang <[email protected]> > --- > kernel/sched/rt.c | 17 +++++++++++++---- > 1 file changed, 13 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index d28cfa4..e6a42e6 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1535,6 +1535,7 @@ static int find_lowest_rq(struct task_struct *task) > struct cpumask *lowest_mask = this_cpu_cpumask_var_ptr(local_cpu_mask); > int this_cpu = smp_processor_id(); > int cpu = task_cpu(task); > + int cachehot_cpu = nr_cpu_ids; > > /* Make sure the mask is initialized first */ > if (unlikely(!lowest_mask)) > @@ -1566,8 +1567,12 @@ static int find_lowest_rq(struct task_struct *task) > > rcu_read_lock(); > for_each_domain(cpu, sd) { > + if (cachehot_cpu >= nr_cpu_ids) > + cachehot_cpu = cpumask_first_and(lowest_mask, > + sched_domain_span(sd)); > + > if (sd->flags & SD_WAKE_AFFINE) { > - int best_cpu; > + int wakeaffine_cpu; > > /* > * "this_cpu" is cheaper to preempt than a > @@ -1579,16 +1584,20 @@ static int find_lowest_rq(struct task_struct *task) > return this_cpu; > } > > - best_cpu = cpumask_first_and(lowest_mask, > + wakeaffine_cpu = cpumask_first_and(lowest_mask, > sched_domain_span(sd)); > - if (best_cpu < nr_cpu_ids) { > + if (wakeaffine_cpu < nr_cpu_ids) { > rcu_read_unlock(); > - return best_cpu; > + return wakeaffine_cpu; > } > } > } > rcu_read_unlock(); > > + /* most likely cache-hot */ > + if (cachehot_cpu < nr_cpu_ids) > + return cachehot_cpu; > + > /* > * And finally, if there were no matches within the domains > * just give the caller *something* to work with from the compatible > -- > 1.9.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
