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

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

On Tue, 2015-03-31 at 14:07 +0530, Preeti U Murthy wrote:
> Hi Jason,
> 
> On 03/31/2015 12:25 AM, Jason Low wrote:
> > Hi Preeti,
> > 
> > I noticed that another commit 4a725627f21d converted the check in
> > nohz_kick_needed() from idle_cpu() to rq->idle_balance, causing a
> > potentially outdated value to be used if this cpu is able to pull tasks
> > using rebalance_domains(), and nohz_kick_needed() directly returning
> > false.
> 
> I see that rebalance_domains() will be run at the end of the scheduler
> tick interrupt handling. trigger_load_balance() only sets the softirq,
> it does not call rebalance_domains() immediately. So the call graph
> would be:

Oh right, since that only sets the softirq, this wouldn't be the issue,
though we would need these changes if we were to incorporate any sort of
nohz_kick_needed() logic into the nohz_idle_balance() code path correct?