Messages in this thread | | | Subject | Re: [patch] sched/fair: Add SIS_MIN_LAT feature to mitigate PELT lag induced stacking | From | Mike Galbraith <> | Date | Wed, 03 Jan 2018 18:24:30 +0100 |
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On Mon, 2018-01-01 at 11:37 +0100, Mike Galbraith wrote: > > > Here 0-day bot, here boy..
Forget it 0-day bot, and assorted crickets :)
> + /* > + * When heavily loaded, stacking may be the best/only latency option, > + * and LAST_BUDDY the only hope of preventing throughput collapse. > + */ > + if (unlikely(task_cfs_rq(current)->nr_running >= sched_nr_latency) && > + task_cfs_rq(p)->nr_running >= sched_nr_latency) > + return target;
With stock knob settings, that's too late to switch from llc -> l2 affinity for sync wakeups, and completely demolished tbench top end on huge socket NUMA box with lots of bandwidth. Lovely for desktop, somewhere below gawd-awful for big box performance.
-Mike
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