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Subject: Re: [PATCH] sched: Reduce the rate of needless idle load balancing
From: Tim Chen <tim.c.chen@linux.intel.com>
To: Joe Perches <joe@perches.com>
Cc: Jason Low <jason.low2@hp.com>, Ingo Molnar <mingo@elte.hu>,
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Date: Wed, 21 May 2014 09:37:47 -0700
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On Tue, 2014-05-20 at 18:15 -0700, Joe Perches wrote:
> On Tue, 2014-05-20 at 14:04 -0700, Tim Chen wrote:
> > On Tue, 2014-05-20 at 13:59 -0700, Tim Chen wrote:
> > > On Tue, 2014-05-20 at 13:51 -0700, Jason Low wrote:
> > > > On Tue, May 20, 2014 at 1:17 PM, Tim Chen <tim.c.chen@linux.intel.com> wrote:
> > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> []
> > > > If we want to do idle load balancing only when it is due for a
> > > > balance, shouldn't the above just be "if (time_after(jiffies,
> > > > rq->next_balance))"?
> > > 
> > > If rq->next_balance and jiffies are equal, then
> > > time_after(jiffies, rq->next_balance) check will be false and
> > > you will not do balance.  But actually you want to balance
> > > for this case so the jiffies+1 was used.
> > 
> > So maybe I should switch the check to 
> > if (time_before(rq->next_balance, jiffies))
> 
> time_after_eq() or time_is_after_eq_jiffies()
> 
> 

I prefer time_after_eq to keep the code style consistent with the
rest of the code in fair.c.

Tim