Messages in this thread | | | Subject | Re: [RFC][PATCH v4 3/3] sched: Periodically decay max cost of idle balance | From | Jason Low <> | Date | Tue, 03 Sep 2013 23:02:59 -0700 |
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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;
> + /* > + * 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?
Here are the AIM7 results with the other 2 patches + this patch with the slightly higher decay value.
---------------------------------------------------------------- workload | % improvement | % improvement | % improvement | with patch | with patch | with patch | 1100-2000 users | 200-1000 users | 10-100 users ---------------------------------------------------------------- alltests | +9.2% | +5.2% | +0.3% ---------------------------------------------------------------- compute | +0.0% | -0.9% | +0.6% ---------------------------------------------------------------- custom | +18.6% | +15.3% | +7.0% ---------------------------------------------------------------- disk | +4.0% | +16.5% | +7.1% ---------------------------------------------------------------- fserver | +64.8% | +27.5% | -0.6% ---------------------------------------------------------------- high_systime | +15.1% | +7.9% | +0.0% ---------------------------------------------------------------- new_fserver | +51.0% | +20.1% | -1.3% ---------------------------------------------------------------- shared | +6.3% | +8.8% | +2.8% ----------------------------------------------------------------
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