On Tue, Jan 07, 2014 at 09:32:04AM +0100, Vincent Guittot wrote: > On 6 January 2014 17:31, Peter Zijlstra <[email protected]> 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
Ah, another way of looking at it is that the avg without blocked component is a 'now' picture. It is the load we are concerned with right now. The more blocked we add the further out we look; with the obvious limit of the entire averaging period. So the avg that is runnable is right now, t_0; the avg that is runnable + blocked is t_0 + p, where p is the avg period over which we expect the blocked contribution to appear. So something like: avg = runnable + p(i) * blocked; where p(i) \e [0,1] could maybe be used to replace the cpu_load array and still represent the concept of looking at a bigger picture for larger sets. Leaving open the details of the map p. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
