From: Yuyang Du <yuyang.du@intel.com>
To: Mike Galbraith <mgalbraith@suse.de>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>,
peterz@infradead.org, mingo@redhat.com, dietmar.eggemann@arm.com,
vincent.guittot@linaro.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 03/16] sched/fair: Disregard idle task wakee_flips in wake_wide
Date: Tue, 24 May 2016 07:17:00 +0800 [thread overview]
Message-ID: <20160523231659.GE18670@intel.com> (raw)
In-Reply-To: <1464018140.3618.8.camel@suse.de>
On Mon, May 23, 2016 at 05:42:20PM +0200, Mike Galbraith wrote:
> On Mon, 2016-05-23 at 15:10 +0100, Morten Rasmussen wrote:
> > On Mon, May 23, 2016 at 03:00:46PM +0200, Mike Galbraith wrote:
> > > On Mon, 2016-05-23 at 13:00 +0100, Morten Rasmussen wrote:
> > >
> > > > The problem then seems to be distinguishing truly idle and busy doing
> > > > interrupts. The issue that I observe is that wake_wide() likes pushing
> > > > tasks around in lightly scenarios which isn't desirable for power
> > > > management. Selecting the same cpu again may potentially let others
> > > > reach deeper C-state.
> > > >
> > > > With that in mind I will if I can do better. Suggestions are welcome :-)
> > >
> > > None here. For big boxen that are highly idle, you'd likely want to
> > > shut down nodes and consolidate load, but otoh, all that slows response
> > > to burst, which I hate. I prefer race to idle, let power gating do its
> > > job. If I had a server farm with enough capacity vs load variability
> > > to worry about, I suspect I'd become highly interested in routing.
> >
> > I don't disagree for systems of that scale, but at the other end of the
> > spectrum it is a single SoC we are trying squeeze the best possible
> > mileage out of. That implies optimizing for power gating to reach deeper
> > C-states when possible by consolidating idle-time and grouping
> > idle cpus. Migrating task unnecessarily isn't helping us in achieving
> > that, unfortunately :-(
>
> Yup, the goals are pretty much mutually exclusive. For your goal, you
> want more of an allocator like behavior, where stacking of tasks is bad
> only once there's too much overlap (ie latency, defining is hard), and
> allocation always has the same order (expand rightward or such for the
> general case, adding little/big complexity for arm). For mine, current
> behavior is good, avoid stacking like the plague.
I'd be happy to have a switch to either one goal.
next prev parent reply other threads:[~2016-05-24 7:14 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-23 10:58 [PATCH 00/16] sched: Clean-ups and asymmetric cpu capacity support Morten Rasmussen
2016-05-23 10:58 ` [PATCH 01/16] sched: Fix power to capacity renaming in comment Morten Rasmussen
2016-05-23 10:58 ` [PATCH 02/16] sched/fair: Consistent use of prev_cpu in wakeup path Morten Rasmussen
2016-06-01 19:49 ` Peter Zijlstra
2016-05-23 10:58 ` [PATCH 03/16] sched/fair: Disregard idle task wakee_flips in wake_wide Morten Rasmussen
2016-05-23 11:12 ` Mike Galbraith
2016-05-23 12:00 ` Morten Rasmussen
2016-05-23 13:00 ` Mike Galbraith
2016-05-23 14:10 ` Morten Rasmussen
2016-05-23 15:42 ` Mike Galbraith
2016-05-23 23:17 ` Yuyang Du [this message]
2016-05-23 23:04 ` Yuyang Du
2016-06-01 19:57 ` Peter Zijlstra
2016-06-02 8:05 ` Peter Zijlstra
2016-06-07 12:08 ` Morten Rasmussen
2016-05-23 10:58 ` [PATCH 04/16] sched/fair: Optimize find_idlest_cpu() when there is no choice Morten Rasmussen
2016-05-24 6:29 ` Mike Galbraith
2016-05-24 8:05 ` Morten Rasmussen
2016-05-24 8:12 ` Mike Galbraith
2016-06-01 19:59 ` Peter Zijlstra
2016-06-07 14:25 ` Morten Rasmussen
2016-05-23 10:58 ` [PATCH 05/16] sched: Introduce SD_ASYM_CPUCAPACITY sched_domain topology flag Morten Rasmussen
2016-05-23 10:58 ` [PATCH 06/16] sched: Disable WAKE_AFFINE for asymmetric configurations Morten Rasmussen
2016-05-24 9:10 ` Vincent Guittot
2016-05-24 10:29 ` Morten Rasmussen
2016-05-24 12:12 ` Vincent Guittot
2016-05-24 13:16 ` Morten Rasmussen
2016-05-24 13:27 ` Vincent Guittot
2016-05-24 13:36 ` Morten Rasmussen
2016-05-24 13:52 ` Vincent Guittot
2016-05-24 15:02 ` Morten Rasmussen
2016-05-24 15:53 ` Vincent Guittot
2016-05-25 9:12 ` Morten Rasmussen
2016-05-26 6:45 ` Vincent Guittot
2016-06-07 16:50 ` Morten Rasmussen
2016-05-23 10:58 ` [PATCH 07/16] sched: Make SD_BALANCE_WAKE a topology flag Morten Rasmussen
2016-05-24 23:52 ` Yuyang Du
2016-05-25 9:27 ` Morten Rasmussen
2016-06-01 20:18 ` Peter Zijlstra
2016-06-08 8:45 ` Morten Rasmussen
2016-05-23 10:58 ` [PATCH 08/16] sched: Store maximum per-cpu capacity in root domain Morten Rasmussen
2016-05-23 10:58 ` [PATCH 09/16] sched/fair: Let asymmetric cpu configurations balance at wake-up Morten Rasmussen
2016-05-24 0:04 ` Yuyang Du
2016-05-24 8:10 ` Morten Rasmussen
2016-05-24 7:03 ` Mike Galbraith
2016-05-24 7:15 ` Mike Galbraith
2016-05-25 6:57 ` Wanpeng Li
2016-05-25 9:49 ` Morten Rasmussen
2016-05-25 10:29 ` Wanpeng Li
2016-05-25 10:54 ` Morten Rasmussen
2016-05-25 11:18 ` Wanpeng Li
2016-06-02 14:21 ` Peter Zijlstra
2016-06-08 11:29 ` Morten Rasmussen
2016-06-08 14:36 ` Peter Zijlstra
2016-05-23 10:58 ` [PATCH 10/16] sched/fair: Compute task/cpu utilization at wake-up more correctly Morten Rasmussen
2016-05-23 10:58 ` [PATCH 11/16] sched/fair: Consider spare capacity in find_idlest_group() Morten Rasmussen
2016-05-23 10:58 ` [PATCH 12/16] sched: Add per-cpu max capacity to sched_group_capacity Morten Rasmussen
2016-05-23 10:58 ` [PATCH 13/16] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups Morten Rasmussen
2016-05-23 10:58 ` [PATCH 14/16] arm: Set SD_ASYM_CPUCAPACITY for big.LITTLE platforms Morten Rasmussen
2016-05-23 10:58 ` [PATCH 15/16] arm: Set SD_BALANCE_WAKE flag for asymmetric capacity systems Morten Rasmussen
2016-05-23 10:58 ` [PATCH 16/16] arm: Update arch_scale_cpu_capacity() to reflect change to define Morten Rasmussen
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