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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