On Thu, Jul 04, 2013 at 06:18:23PM +0530, Srikar Dronamraju wrote:
> * Mel Gorman <mgorman@xxxxxxx> [2013-07-03 15:21:38]:
>
> > task_numa_placement checks current->mm but after buffers for faults
> > have already been uselessly allocated. Move the check earlier.
> >
> > [peterz@xxxxxxxxxxxxx: Identified the problem]
> > Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
> > ---
> > kernel/sched/fair.c | 22 ++++++++++++++--------
> > 1 file changed, 14 insertions(+), 8 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 336074f..3c796b0 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -870,8 +870,6 @@ static void task_numa_placement(struct task_struct *p)
> > int seq, nid, max_nid = 0;
> > unsigned long max_faults = 0;
> >
> > - if (!p->mm) /* for example, ksmd faulting in a user's mm */
> > - return;
> > seq = ACCESS_ONCE(p->mm->numa_scan_seq);
> > if (p->numa_scan_seq == seq)
> > return;
> > @@ -945,6 +943,12 @@ void task_numa_fault(int last_nid, int node, int pages, bool migrated)
> > if (!sched_feat_numa(NUMA))
> > return;
> >
> > + /* for example, ksmd faulting in a user's mm */
> > + if (!p->mm) {
> > + p->numa_scan_period = sysctl_numa_balancing_scan_period_max;
>
> Naive question:
> Why are we resetting the scan_period?
>
At the time I wrote it I was thinking of tick times and meant to recheck
if it's necessary but then it slipped my mind. The reset is unnecessary
as curr->mm is already checked.
--
Mel Gorman
SUSE Labs
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