On Tue, 2008-06-24 at 11:58 +0200, Peter Zijlstra wrote: > On Mon, 2008-06-23 at 17:04 -0600, Gregory Haskins wrote: > > A system that tends to overschedule (such as PREEMPT_RT) will naturally > > tend to newidle balance often as well. This may have quite a negative > > impact on performance. This patch attempts to address the overzealous > > newidle balancing by only allowing it to occur if the previous task > > was SCHED_OTHER. > > > > Some may argue that if the system is going idle, it should try to > > newidle balance to keep it doing useful work. But the fact is that > > spending too much time in the load-balancing code demonstrably hurts > > performance as well. Running oprofile on the system with various > > workloads has shown that we can sometimes spend a majority of our > > cpu-time running load_balance_newidle. Additionally, disabling > > newidle balancing can make said workloads increase in performance by > > up to 200%. Obviously disabling the feature outright is not sustainable, > > but hopefully we can make it smarter. > > > > This code assumes that if there arent any CFS tasks present on the queue, > > it was probably already balanced. > > > > Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx> > > NAK, this wrecks idle balance for any potential other classes. > > idle_balance() is the generical hook - as can be seen from the class > iteration in move_tasks(). > > I can imagine paritioned EDF wanting to make use of these hooks to > balance the reservations. Hmm, it wouldn't,.. since its too tied in with fbg which is sched_other based,.. would need more generalization work,.. -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
