On Tue, Dec 10, 2013 at 02:22:11PM -0800, Andrew Morton wrote:
> On Tue, 10 Dec 2013 15:51:35 +0000 Mel Gorman <mgorman@xxxxxxx> wrote:
>
> > This patch adds three tracepoints
> > o trace_sched_move_numa when a task is moved to a node
> > o trace_sched_swap_numa when a task is swapped with another task
> > o trace_sched_stick_numa when a numa-related migration fails
> >
> > The tracepoints allow the NUMA scheduler activity to be monitored and the
> > following high-level metrics can be calculated
> >
> > o NUMA migrated stuck nr trace_sched_stick_numa
> > o NUMA migrated idle nr trace_sched_move_numa
> > o NUMA migrated swapped nr trace_sched_swap_numa
> > o NUMA local swapped trace_sched_swap_numa src_nid == dst_nid (should never happen)
> > o NUMA remote swapped trace_sched_swap_numa src_nid != dst_nid (should == NUMA migrated swapped)
> > o NUMA group swapped trace_sched_swap_numa src_ngid == dst_ngid
> > Maybe a small number of these are acceptable
> > but a high number would be a major surprise.
> > It would be even worse if bounces are frequent.
> > o NUMA avg task migs. Average number of migrations for tasks
> > o NUMA stddev task mig Self-explanatory
> > o NUMA max task migs. Maximum number of migrations for a single task
> >
> > In general the intent of the tracepoints is to help diagnose problems
> > where automatic NUMA balancing appears to be doing an excessive amount of
> > useless work.
> >
> > ...
> >
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -1272,11 +1272,13 @@ static int task_numa_migrate(struct task_struct *p)
> > p->numa_scan_period = task_scan_min(p);
> >
> > if (env.best_task == NULL) {
> > - int ret = migrate_task_to(p, env.best_cpu);
> > + if ((ret = migrate_task_to(p, env.best_cpu)) != 0)
> > + trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
> > return ret;
> > }
> >
> > - ret = migrate_swap(p, env.best_task);
> > + if ((ret = migrate_swap(p, env.best_task)) != 0);
>
> I'll zap that semicolon...
>
Thanks
--
Mel Gorman
SUSE Labs
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