Re: [PATCH 7/8] sched: prevent to re-select dst-cpu inload_balance()

From: Peter Zijlstra
Date: Wed Mar 20 2013 - 08:38:38 EST


On Wed, 2013-03-20 at 16:43 +0900, Joonsoo Kim wrote:
> On Tue, Mar 19, 2013 at 04:05:46PM +0100, Peter Zijlstra wrote:
> > On Thu, 2013-02-14 at 14:48 +0900, Joonsoo Kim wrote:
> > > Commit 88b8dac0 makes load_balance() consider other cpus in its group.
> > > But, in that, there is no code for preventing to re-select dst-cpu.
> > > So, same dst-cpu can be selected over and over.
> > >
> > > This patch add functionality to load_balance() in order to exclude
> > > cpu which is selected once.
> >
> > Oh man.. seriously? Did you see this happen? Also, can't we simply
> > remove it from lb->cpus?
>
> I didn't see it, I do just logical thinking. :)
> lb->cpus is for source cpus and dst-cpu is for dest cpus. So, it doesn't
> works to remove it from lb->cpus.

How about we interpret ->cpus as the total mask to balance; so both
source and destination. That way clearing a cpu means we won't take nor
put tasks on it.

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