On Fri, May 16, 2014 at 12:13:32AM -0400, Rik van Riel wrote: > Affine wakeups have the potential to interfere with NUMA placement. > If a task wakes up too many other tasks, affine wakeups will get > disabled. > > However, regardless of how many other tasks it wakes up, it gets > re-enabled once a second, potentially interfering with NUMA > placement of other tasks. > > By decaying wakee_wakes in half instead of zeroing it, we can avoid > that problem for some workloads.
See https://lkml.org/lkml/2013/7/2/110 and further > Signed-off-by: Rik van Riel <r...@redhat.com> > --- > kernel/sched/fair.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 4f01e2f1..0381b11 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4009,7 +4009,7 @@ static void record_wakee(struct task_struct *p) > * about the loss. > */ > if (jiffies > current->wakee_flip_decay_ts + HZ) { > - current->wakee_flips = 0; > + current->wakee_flips >>= 1; > current->wakee_flip_decay_ts = jiffies; > } Would it make sense to do something like: now = jiffies; while (current->wakee_flips && now > current->wakee_flip_decay_ts + HZ) { current->wakee_flips >>= 1; current->wakee_flip_decay_ts += HZ; } if (unlikely(now > current->wakee_flip_decay_ts + HZ)) current->wakee_flip_decay_ts = now; Or is that over engineering things?
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