On Fri, 2014-04-25 at 09:58 +0200, Mike Galbraith wrote: > On Fri, 2014-04-25 at 00:13 -0700, Jason Low wrote: > > On Fri, 2014-04-25 at 10:42 +0530, Preeti U Murthy wrote: > > > I agree with this. However I am concerned with an additional point that > > > I have mentioned in my reply to Peter's mail on this thread. > > > > > > Should we verify if rq->next_balance update is independent of > > > pulled_tasks? sd->balance_interval is changed during load_balance() and > > > rq->next_balance should perhaps consider that? > > > > Hi Preeti, > > > > I agree that we may want to consider having rq->next balance update be > > independent of pulled_task. As you mentioned, load_balance() can modify > > the balance_interval. > > > > There are a few things I'm wondering if we would need to also add then: > > > > 1. In the case that this_rq->avg_idle < sysctl_sched_migration_cost, we > > would need to also traverse the domains to properly compute > > next_balance (without the sd->busy_factor) as we would be going idle. > > Otherwise, next_balance could get set to jiffies + HZ while the > > CPU goes idle. > > Avoiding high frequency cache misses and cycle wastage on micro-idle was > what avg-idle was about. If you're going to traverse anyway, or have a > better way to not do that too frequently, you can just nuke it.
Yeah, we already compare avg-idle with the per-domain costs in that function. I'll run some performance tests with the first check removed, as such a change can potentially have a (+/-) impact on performance. Thanks, Jason -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
