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    SubjectRe: [PATCH 08/18] sched: Reschedule task on preferred NUMA node once selected
    * Mel Gorman <mgorman@suse.de> [2013-07-15 16:20:10]:

    > A preferred node is selected based on the node the most NUMA hinting
    > faults was incurred on. There is no guarantee that the task is running
    > on that node at the time so this patch rescheules the task to run on
    > the most idle CPU of the selected node when selected. This avoids
    > waiting for the balancer to make a decision.
    >
    > Signed-off-by: Mel Gorman <mgorman@suse.de>
    > ---
    > kernel/sched/core.c | 17 +++++++++++++++++
    > kernel/sched/fair.c | 46 +++++++++++++++++++++++++++++++++++++++++++++-
    > kernel/sched/sched.h | 1 +
    > 3 files changed, 63 insertions(+), 1 deletion(-)
    >
    > diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    > index 5e02507..b67a102 100644
    > --- a/kernel/sched/core.c
    > +++ b/kernel/sched/core.c
    > @@ -4856,6 +4856,23 @@ fail:
    > return ret;
    > }
    >
    > +#ifdef CONFIG_NUMA_BALANCING
    > +/* Migrate current task p to target_cpu */
    > +int migrate_task_to(struct task_struct *p, int target_cpu)
    > +{
    > + struct migration_arg arg = { p, target_cpu };
    > + int curr_cpu = task_cpu(p);
    > +
    > + if (curr_cpu == target_cpu)
    > + return 0;
    > +
    > + if (!cpumask_test_cpu(target_cpu, tsk_cpus_allowed(p)))
    > + return -EINVAL;
    > +
    > + return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg);

    As I had noted earlier, this upsets schedstats badly.
    Can we add a TODO for this patch, which mentions that schedstats need to
    taken care.

    One alternative that I can think of is to have a per scheduling class
    routine that gets called and does the needful.
    for example: for fair share, it could update the schedstats as well as
    check for cfs_throttling.

    But I think its an issue that needs some fix or we should obsolete
    schedstats.



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