Messages in this thread | | | Date | Mon, 9 Sep 2013 13:49:19 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH v4 3/3] sched: Periodically decay max cost of idle balance |
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On Wed, Sep 04, 2013 at 12:10:01AM -0700, Jason Low wrote: > On Fri, 2013-08-30 at 12:18 +0200, Peter Zijlstra wrote: > > On Thu, Aug 29, 2013 at 01:05:36PM -0700, Jason Low wrote: > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > > index 58b0514..bba5a07 100644 > > > --- a/kernel/sched/core.c > > > +++ b/kernel/sched/core.c > > > @@ -1345,7 +1345,7 @@ ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) > > > > > > if (rq->idle_stamp) { > > > u64 delta = rq_clock(rq) - rq->idle_stamp; > > > - u64 max = 2*rq->max_idle_balance_cost; > > > + u64 max = 2*(sysctl_sched_migration_cost + rq->max_idle_balance_cost); > > > > You re-introduce sched_migration_cost here because max_idle_balance_cost > > can now drop down to 0 again? > > Yes it was so that max_idle_balance_cost would be at least sched_migration_cost > and that we would still skip idle_balance if avg_idle < sched_migration_cost. > > I also initially thought that adding sched_migration_cost would also account for > the extra "costs" of idle balancing that are not accounted for in the time spent > on each newidle load balance. Come to think of it though, sched_migration_cost > might be too large when used in that context considering we're already using the > max cost.
Right, so shall we do as Srikar suggests and drop that initial check?
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