From: Mike Galbraith <efault@gmx.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch] sched/fair: Add SIS_MIN_LAT feature to mitigate PELT lag induced stacking
Date: Wed, 03 Jan 2018 18:24:30 +0100 [thread overview]
Message-ID: <1515000270.6513.78.camel@gmx.de> (raw)
In-Reply-To: <1514803074.8330.8.camel@gmx.de>
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
prev parent reply other threads:[~2018-01-03 17:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-01 10:37 [patch] sched/fair: Add SIS_MIN_LAT feature to mitigate PELT lag induced stacking Mike Galbraith
2018-01-03 17:24 ` Mike Galbraith [this message]
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