On Fri, Jun 28, 2013 at 11:44:28AM +0530, Srikar Dronamraju wrote:
> * Mel Gorman <mgorman@xxxxxxx> [2013-06-26 15:38:02]:
>
> > This patch selects a preferred node for a task to run on based on the
> > NUMA hinting faults. This information is later used to migrate tasks
> > towards the node during balancing.
> >
> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> > ---
> > include/linux/sched.h | 1 +
> > kernel/sched/core.c | 10 ++++++++++
> > kernel/sched/fair.c | 16 ++++++++++++++--
> > kernel/sched/sched.h | 2 +-
> > 4 files changed, 26 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index 72861b4..ba46a64 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -1507,6 +1507,7 @@ struct task_struct {
> > struct callback_head numa_work;
> >
> > unsigned long *numa_faults;
> > + int numa_preferred_nid;
> > #endif /* CONFIG_NUMA_BALANCING */
> >
> > struct rcu_head rcu;
> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> > index f332ec0..019baae 100644
> > --- a/kernel/sched/core.c
> > +++ b/kernel/sched/core.c
> > @@ -1593,6 +1593,7 @@ static void __sched_fork(struct task_struct *p)
> > p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
> > p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0;
> > p->numa_scan_period = sysctl_numa_balancing_scan_delay;
> > + p->numa_preferred_nid = -1;
>
> Though we may not want to inherit faults, I think the tasks generally
> share pages with their siblings, parent. So will it make sense to
> inherit the preferred node?
>
If it really shared data with its parent then it will be detected by the PTE
scanner later as normal. I would expect that initially it would be scheduled
to run on CPUs on the local node and I would think that inheriting it here
will not make a detectable difference. If you think it will, I can do it
but then the data should certainly be cleared on exec.
--
Mel Gorman
SUSE Labs
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