* Srikar Dronamraju <[email protected]> wrote:
> > So I find the patch, the description and the comments in the code
> > conflicting and
> > confusing.
> >
> > The patch does this:
> >
> > @@ -5676,10 +5676,10 @@ static int migrate_degrades_locality(struct
> > task_struct *p, struct lb_env *env)
> > unsigned long src_faults, dst_faults;
> > int src_nid, dst_nid;
> >
> > - if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
> > + if (!sched_feat(NUMA) || !sched_feat(NUMA_FAVOUR_HIGHER))
> > return -1;
> >
> > - if (!sched_feat(NUMA))
> > + if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
> > return -1;
> >
> > src_nid = cpu_to_node(env->src_cpu);
> >
> >
> > while the default for 'NUMA' is 0, 'NUMA_FAVOUR_HIGHER' is 1.
> >
> > Which in itself is confusing: WTH do we have a generic switch called 'NUMA'
> > and
> > then have it disabled?
>
> NUMA feature gets enabled on multi-node boxes because of
>
> start_kernel() -> numa_policy_init() -> check_numabalancing_enable() ->
> set_numabalancing_state() -> sched_feat_set("NUMA");
Ugh, that is nonsensical!
If CONFIG_SCHED_DEBUG is disabled then sched_features is a constant value:
# define const_debug const
...
extern const_debug unsigned int sysctl_sched_features;
sched_features are _only_ meant for debugging. They turn into an unchangeable
set
of features when SCHED_DEBUG is disabled - and that is very much by design.
The whole set_numabalancing_state() muck needs to be fixed.
Thanks,
Ingo
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