On 29 July 2014 17:27, Peter Zijlstra <pet...@infradead.org> wrote: > On Tue, Jul 29, 2014 at 04:59:10PM +0200, Peter Zijlstra wrote: >> On Tue, Jul 29, 2014 at 11:04:50AM +0200, Vincent Guittot wrote: >> > > In situations where all the domains are overloaded, or where only the >> > > busiest domain is overloaded, that code is also superfluous, since >> > > the normal env->imbalance calculation will figure out how much to move. >> > > Remove the load_above_capacity calculation. >> > >> > IMHO, we should not remove that part which is used by prefer_sibling >> > >> > Originally, we had 2 type of busiest group: overloaded or imbalanced. >> > You add a new one which has only a avg_load higher than other so you >> > should handle this new case and keep the other ones unchanged >> >> Right, so we want that code for overloaded -> overloaded migrations such >> as not to cause idle cpus in an attempt to balance things. Idle cpus are >> worse than imbalance. >> >> But in case of overloaded/imb -> !overloaded migrations we can allow it, >> and in fact want to allow it in order to balance idle cpus. > > Which would be patch 3/2
FWIW, you can add my ack for the new version of the patchset which includes this patch > > --- > Subject: sched,fair: Allow calculate_imbalance() to move idle cpus > From: Peter Zijlstra <pet...@infradead.org> > Date: Tue Jul 29 17:15:11 CEST 2014 > > Allow calculate_imbalance() to 'create' idle cpus in the busiest group > if there are idle cpus in the local group. > > Suggested-by: Rik van Riel <r...@redhat.com> > Signed-off-by: Peter Zijlstra <pet...@infradead.org> > Link: http://lkml.kernel.org/n/tip-7k95k4i2tjv78iivstggi...@git.kernel.org > --- > kernel/sched/fair.c | 11 +++++------ > 1 file changed, 5 insertions(+), 6 deletions(-) > > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6273,12 +6273,11 @@ static inline void calculate_imbalance(s > return fix_small_imbalance(env, sds); > } > > - if (busiest->group_type == group_overloaded) { > - /* > - * Don't want to pull so many tasks that a group would go > idle. > - * Except of course for the group_imb case, since then we > might > - * have to drop below capacity to reach cpu-load equilibrium. > - */ > + /* > + * If there aren't any idle cpus, avoid creating some. > + */ > + if (busiest->group_type == group_overloaded && > + local->group_type == group_overloaded) { > load_above_capacity = > (busiest->sum_nr_running - > busiest->group_capacity_factor); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
