Messages in this thread Patch in this message | | | Subject | Re: [PATCH] sched: Only migrate tasks due to interrupts on an idle CPU if prev and target CPUs share cache | From | Mike Galbraith <> | Date | Fri, 15 Dec 2017 21:38:06 +0100 |
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On Fri, 2017-12-15 at 16:52 +0000, Mel Gorman wrote: > > It's a small improvement...
From my log on corr.arch.suse.de (2x8 box)
4.15.0.g2db767d-default Throughput 2665.88 MB/sec 8 clients 8 procs max_latency=21.472 ms 4.15.0.g2db767d-default NO_WA_IDLE Throughput 3416.35 MB/sec 8 clients 8 procs max_latency=9.825 ms
Not so small improvement. WA_IDLE ripped corr up pretty bad, turning it off restored 4.4 performance.
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > --- > kernel/sched/fair.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 2fe3aa853e4d..4a1f7d32ecf6 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5701,7 +5701,13 @@ static bool > wake_affine_idle(struct sched_domain *sd, struct task_struct *p, > int this_cpu, int prev_cpu, int sync) > { > - if (idle_cpu(this_cpu)) > + /* > + * If this_cpu is idle, it implies the wakeup is from interrupt > + * context. Only allow the move if cache is shared. Otherwise an > + * interrupt intensive workload could force all tasks onto one > + * node depending on the IO topology or IRQ affinity settings. > + */ > + if (idle_cpu(this_cpu) && cpus_share_cache(this_cpu, prev_cpu)) > return true; > > if (sync && cpu_rq(this_cpu)->nr_running == 1)
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