Re: [PATCH v2] sched: Fast idling of CPU when system is partially loaded

[Jason Low]

On Mon, 2014-06-23 at 18:22 +0200, Andi Kleen wrote:
> > So I don't get why we can't do the below; I think Jason tried to ask the
> > same...
> 
> The important part for performance is to minimize the cache line transfers. Your
> unconditional variant would cause more dirty cache lines than Tim's,
> right?

How about that change to the update_sg_lb_stats() call site along with:

                sgs->group_load += load;
                sgs->sum_nr_running += rq->nr_running;
-               if (overload && rq->nr_running > 1)
+               if (!env->sd->parent && rq->nr_running > 1)
                        *overload = true;

which keeps it as a conditional to avoid unnecessarily setting overload
when it's not used, and still get those benefits Peter mentioned.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/