linux-kernel - Re: [PATCH 7/8] sched: prevent to re-select dst-cpu in load

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Date:	Wed, 20 Mar 2013 22:48:32 +0900
From:	JoonSoo Kim <js1304@...il.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/8] sched: prevent to re-select dst-cpu in load_balance()

2013/3/20 Peter Zijlstra <peterz@...radead.org>:
> 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.

In my quick thought, it may be possible.
I will try to do it.

Thanks.

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