Re: [RFC] sched: CPU topology try

[Vincent Guittot <vincent.guittot@linaro.org>]

On 6 January 2014 17:31, Peter Zijlstra <peterz@infradead.org> wrote:
> On Mon, Jan 06, 2014 at 02:41:31PM +0100, Vincent Guittot wrote:
>> IMHO, these settings will disappear sooner or later, as an example the
>> idle/busy _idx are going to be removed by Alex's patch.
>
> Well I'm still entirely unconvinced by them..
>
> removing the cpu_load array makes sense, but I'm starting to doubt the
> removal of the _idx things.. I think we want to retain them in some
> form, it simply makes sense to look at longer term averages when looking
> at larger CPU groups.
>
> So maybe we can express the things in log_2(group-span) or so, but we
> need a working replacement for the cpu_load array. Ideally some
> expression involving the blocked load.

Using the blocked load can surely give benefit in the load balance
because it gives a view of potential load on a core but it still decay
with the same speed than runnable load average so it doesn't solve the
issue for longer term average. One way is to have a runnable average
load with longer time window

>
> Its another one of those things I need to ponder more :-)