Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 16 Oct 2019 13:56:49 +0200 | Subject | Re: [PATCH v3 04/10] sched/fair: rework load_balance |
| |
On Wed, 16 Oct 2019 at 09:21, Parth Shah <parth@linux.ibm.com> wrote: > > > > On 9/19/19 1:03 PM, Vincent Guittot wrote: > > [...] > > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> > > --- > > kernel/sched/fair.c | 585 ++++++++++++++++++++++++++++++++++------------------ > > 1 file changed, 380 insertions(+), 205 deletions(-) > > > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > > index 017aad0..d33379c 100644 > > --- a/kernel/sched/fair.c > > +++ b/kernel/sched/fair.c > > @@ -7078,11 +7078,26 @@ static unsigned long __read_mostly max_load_balance_interval = HZ/10; > > > > enum fbq_type { regular, remote, all }; > > > > +/* > > + * group_type describes the group of CPUs at the moment of the load balance. > > + * The enum is ordered by pulling priority, with the group with lowest priority > > + * first so the groupe_type can be simply compared when selecting the busiest > > + * group. see update_sd_pick_busiest(). > > + */ > > enum group_type { > > - group_other = 0, > > + group_has_spare = 0, > > + group_fully_busy, > > group_misfit_task, > > + group_asym_packing, > > group_imbalanced, > > - group_overloaded, > > + group_overloaded > > +}; > > + > > +enum migration_type { > > + migrate_load = 0, > > + migrate_util, > > + migrate_task, > > + migrate_misfit > > }; > > > > #define LBF_ALL_PINNED 0x01 > > @@ -7115,7 +7130,7 @@ struct lb_env { > > unsigned int loop_max; > > > > enum fbq_type fbq_type; > > - enum group_type src_grp_type; > > + enum migration_type balance_type; > > struct list_head tasks; > > }; > > > > @@ -7347,7 +7362,7 @@ static int detach_tasks(struct lb_env *env) > > { > > struct list_head *tasks = &env->src_rq->cfs_tasks; > > struct task_struct *p; > > - unsigned long load; > > + unsigned long util, load; > > int detached = 0; > > > > lockdep_assert_held(&env->src_rq->lock); > > @@ -7380,19 +7395,53 @@ static int detach_tasks(struct lb_env *env) > > if (!can_migrate_task(p, env)) > > goto next; > > > > - load = task_h_load(p); > > + switch (env->balance_type) { > > + case migrate_load: > > + load = task_h_load(p); > > > > - if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed) > > - goto next; > > + if (sched_feat(LB_MIN) && > > + load < 16 && !env->sd->nr_balance_failed) > > + goto next; > > > > - if ((load / 2) > env->imbalance) > > - goto next; > > + if ((load / 2) > env->imbalance) > > + goto next; > > + > > + env->imbalance -= load; > > + break; > > + > > + case migrate_util: > > + util = task_util_est(p); > > + > > + if (util > env->imbalance) > > Can you please explain what would happen for > `if (util/2 > env->imbalance)` ? > just like when migrating load, even util shouldn't be migrated if > env->imbalance is just near the utilization of the task being moved, isn't it?
I have chosen uti and not util/2 to be conservative because migrate_util is used to fill spare capacity. With `if (util/2 > env->imbalance)`, we can more easily overload the local group or pick too much utilization from the overloaded group.
> > > + goto next; > > + > > + env->imbalance -= util; > > + break; > > +[ ... ] > > Thanks, > Parth >
| |