From: Peter Zijlstra <peterz@infradead.org>
To: Mike Galbraith <efault@gmx.de>
Cc: Mel Gorman <mgorman@techsingularity.net>,
Ingo Molnar <mingo@kernel.org>,
Vincent Guittot <vincent.guittot@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Aubrey Li <aubrey.li@linux.intel.com>,
Barry Song <song.bao.hua@hisilicon.com>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running
Date: Tue, 5 Oct 2021 11:24:23 +0200 [thread overview]
Message-ID: <YVwZx1Mc6FQdWY6J@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <0cf76bb7701d4a37367773881c7d7c7bfceb455e.camel@gmx.de>
On Tue, Sep 21, 2021 at 02:32:54PM +0200, Mike Galbraith wrote:
> On Tue, 2021-09-21 at 11:36 +0100, Mel Gorman wrote:
> > FAIR_SLEEPERS primarily affects tasks that just became runnable and the
> > new task is trying to fit in without causing too much disruption based
> > on sysctl_sched_latency.
>
> No, fair sleepers is all about sleeper wakeup preemption, I think
> you're thinking of fork initial placement.
Butting in in the middle of the thread (and I know there's still lots to
read)...
So the FAIR_SLEEPERS thing is about giving tasks that have slept a while
some extra credit to run sooner.
The classical example has always been a task that run 50% combined with
a task that runs 100%, what's fair? a 1:2 or 1:1 ratio? Strict fair
(runnable) scheduling will get you the 1:2, while intuitively having two
tasks with 100% combined CPU utilization 1:1 would be 'fair'.
FAIR_SLEEPERS gets you towards that 1:1, *provided* the period of that
50% is near sched_latency/2.
Another important factor for wakeup preemption has always been desktop
usage; can you still get responsive terminals while building a kernel,
how does firefox scroll during a kernel build etc..
(fwiw, firefox should start scrolling responsively and then bog down if
you keep on scrolling because it becomes a hog and has exhausted the
inital boost)
Also, I think the ChromeOS people have interactivity measures these
days.
All our traditinoal benchmarks miss out here; they're mostly throughput
oriented, and it is really easy to totally wreck interactivity while
getting great througput :/
next prev parent reply other threads:[~2021-10-05 9:26 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 14:26 [PATCH 0/2] Scale wakeup granularity relative to nr_running Mel Gorman
2021-09-20 14:26 ` [PATCH 1/2] sched/fair: Remove redundant lookup of rq in check_preempt_wakeup Mel Gorman
2021-09-21 7:21 ` Vincent Guittot
2021-09-21 7:53 ` Mel Gorman
2021-09-21 8:12 ` Vincent Guittot
2021-09-21 8:21 ` Peter Zijlstra
2021-09-21 10:03 ` Mel Gorman
2021-09-20 14:26 ` [PATCH 2/2] sched/fair: Scale wakeup granularity relative to nr_running Mel Gorman
2021-09-21 3:52 ` Mike Galbraith
2021-09-21 5:50 ` Mike Galbraith
2021-09-21 7:04 ` Mike Galbraith
2021-09-21 10:36 ` Mel Gorman
2021-09-21 12:32 ` Mike Galbraith
2021-09-21 14:03 ` Mel Gorman
2021-10-05 9:24 ` Peter Zijlstra [this message]
2021-09-22 5:22 ` Mike Galbraith
2021-09-22 13:20 ` Mel Gorman
2021-09-22 14:04 ` Mike Galbraith
2021-09-22 14:15 ` Vincent Guittot
2021-09-22 15:04 ` Mel Gorman
2021-09-22 16:00 ` Vincent Guittot
2021-09-22 17:38 ` Mel Gorman
2021-09-22 18:22 ` Vincent Guittot
2021-09-22 18:57 ` Mel Gorman
2021-09-23 1:47 ` Mike Galbraith
2021-09-23 8:40 ` Vincent Guittot
2021-09-23 9:21 ` Mike Galbraith
2021-09-23 12:41 ` Vincent Guittot
2021-09-23 13:14 ` Mike Galbraith
2021-09-27 11:17 ` Mel Gorman
2021-09-27 14:17 ` Mike Galbraith
2021-10-04 8:05 ` Mel Gorman
2021-10-04 16:37 ` Vincent Guittot
2021-10-05 7:41 ` Mel Gorman
2021-09-27 14:19 ` Vincent Guittot
2021-09-27 15:02 ` Mel Gorman
2021-09-23 12:24 ` Phil Auld
2021-10-05 10:36 ` Peter Zijlstra
2021-10-05 14:12 ` Phil Auld
2021-10-05 14:32 ` Peter Zijlstra
2021-10-05 10:28 ` Peter Zijlstra
2021-10-05 10:23 ` Peter Zijlstra
2021-10-05 9:41 ` Peter Zijlstra
2021-09-22 15:05 ` Vincent Guittot
2021-10-05 9:32 ` Peter Zijlstra
2021-10-03 3:07 ` wakeup_affine_weight() is b0rked - was " Mike Galbraith
2021-10-03 7:34 ` Barry Song
2021-10-03 14:52 ` Mike Galbraith
2021-10-03 21:06 ` Barry Song
2021-10-04 1:49 ` Mike Galbraith
2021-10-04 4:34 ` Mike Galbraith
2021-10-04 9:06 ` Mike Galbraith
2021-10-05 7:47 ` Mel Gorman
2021-10-05 8:42 ` Mike Galbraith
2021-10-05 9:31 ` Mel Gorman
2021-10-06 6:46 ` Mike Galbraith
2021-10-08 5:06 ` Mike Galbraith
2021-09-21 8:03 ` Vincent Guittot
2021-09-21 10:45 ` Mel Gorman
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