Re: sched: Improve load balancing in the presence of idle CPUs

[Jason Low <jason.low2@hp.com>]

On Sat, 2015-04-04 at 15:29 +0530, Preeti U Murthy wrote:

> Solution 1: As exists in the mainline
> Solution 2: nohz_idle_balance(); rebalance_domains() on the ILB CPU
> Solution 3: Above patch.
> 
> I observe that Solution 3 is not as aggressive in spreading load as
> Solution 2. With Solution 2, the load gets spread within the first 3-4
> seconds,

hmm, so 3-4 seconds still sounds like a long time.

> while with Solution3, the load gets spread within the first 6-7
> seconds. I think this is because, the above patch decides to further
> nohz_idle_load_balance() based on the load on the current ILB CPU which
> has most likely pulled just one task.

Okay, so perhaps we can also try continuing nohz load balancing if we
find that there are overloaded CPUs in the system.