On Mon, 2013-09-09 at 13:44 +0200, Peter Zijlstra wrote:
> On Tue, Sep 03, 2013 at 11:02:59PM -0700, Jason Low wrote:
> > On Fri, 2013-08-30 at 12:29 +0200, Peter Zijlstra wrote:
> > > rcu_read_lock();
> > > for_each_domain(cpu, sd) {
> > > + /*
> > > + * Decay the newidle max times here because this is a regular
> > > + * visit to all the domains. Decay ~0.5% per second.
> > > + */
> > > + if (time_after(jiffies, sd->next_decay_max_lb_cost)) {
> > > + sd->max_newidle_lb_cost =
> > > + (sd->max_newidle_lb_cost * 254) / 256;
> >
> > I initially picked 0.5%, but after trying it out, it appears to decay very
> > slowing when the max is at a high value. Should we increase the decay a
> > little bit more? Maybe something like:
> >
> > sd->max_newidle_lb_cost = (sd->max_newidle_lb_cost * 63) / 64;
>
> So the half-life in either case is is given by:
>
> n = ln(1/2) / ln(x)
>
> which gives 88 seconds for x := 254/256 or 44 seconds for x := 63/64.
>
> I don't really care too much, but obviously something like:
>
> 256*exp(ln(.5)/60) ~= 253
>
> Is attractive ;-)
>
> > > + /*
> > > + * Stop the load balance at this level. There is another
> > > + * CPU in our sched group which is doing load balancing more
> > > + * actively.
> > > + */
> > > + if (!continue_balancing) {
> >
> > Is "continue_balancing" named "balance" in older kernels?
>
> Yeah, this patch crossed paths with a series remodeling the
> load-balancer a bit, that should all be pushed-out to tip/master.
>
> In particular see commit:
> 23f0d20 sched: Factor out code to should_we_balance()
>
> > Here are the AIM7 results with the other 2 patches + this patch with the
> > slightly higher decay value.
>
> Just to clarify, 'this patch' is the one I sent?
Yes, I was referring to the one you sent out. Also, I did the
s/smp_processor_id()/this_cpu/ on patch 2.
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