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SubjectRe: [PATCH] sched/numa: Restore sched feature NUMA to its earlier avatar.

* Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote:

> > > > 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.
>
> Would something like the below suffice. If yes I can send out a formal
> patch for the same. Here we are moving numabalancing_enabled variable to
> common i.e for both CONFIG_SCHED_DEBUG and !CONFIG_SCHED_DEBUG.
>
> Also removing sched_feat_numa because its no more getting used.
> numabalancing_enabled is already being used similarly in task_tick_fair
> and task_numa_fault.
>
> -------------->8------------------------------------------------------8<--------------
>
> kernel/sched/core.c | 5 +++--
> kernel/sched/fair.c | 2 +-
> kernel/sched/sched.h | 6 ------
> 3 files changed, 4 insertions(+), 9 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 78b4bad10..69ccbda4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -2059,17 +2059,18 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
> }
>
> #ifdef CONFIG_NUMA_BALANCING
> +__read_mostly bool numabalancing_enabled;

s/numabalancing_enabled/sched_numa_balancing

Other than that this would be OK.

Thanks,

Ingo


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