linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Morten Rasmussen <morten.rasmussen@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Chris Redpath <chris.redpath@arm.com>,
	Valentin Schneider <valentin.schneider@arm.com>,
	LAK <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] sched: support dynamiQ cluster
Date: Fri, 13 Apr 2018 10:11:36 +0100	[thread overview]
Message-ID: <20180413091136.GV4589@e105550-lin.cambridge.arm.com> (raw)
In-Reply-To: <20180412182211.GC4082@hirez.programming.kicks-ass.net>

On Thu, Apr 12, 2018 at 08:22:11PM +0200, Peter Zijlstra wrote:
> On Tue, Apr 10, 2018 at 02:19:50PM +0100, Morten Rasmussen wrote:
> > As said above, I see your point about completion time might suffer in
> > some cases for low utilization tasks, but I don't see how you can fix
> > that automagically. ASYM_PACKING has a lot of problematic side-effects.
> > If use-space knows that completion time is important for a task, there
> > are already ways to improve that somewhat in mainline (task priority and
> > pinning), and more powerful solutions in the Android kernel which
> > Patrick is currently pushing upstream.
> 
> So I tend to side with Morten on this one. I don't particularly like
> ASYM_PACKING much, but we already had it for PPC and it works for the
> small difference in performance ITMI has.
> 
> At the time Morten already objected to using it for ITMI, and I just
> haven't had time to look into his proposal for using capacity.
> 
> But I don't see it working right for big.litte/dynamiq, simply because
> it is a very strong always big preference, which is against the whole
> design premisis of big.little (as Morten has been trying to argue).

In Vincent's defence, vendors do sometimes make design decisions that I
don't quite understand. So there could be users that really want a
non-energy-aware big-first policy, but as I said earlier in this thread,
that could be implemented better with a small tweak to wake_cap() and
using the misfit patches.

We would have to disable big-first policy and go with the current
migrate-big-task-to-big-cpus policy as soon as we care about energy. I'm
happy to give that try and come up with a patch.

  reply	other threads:[~2018-04-13  9:11 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-28  7:46 [PATCH] sched: support dynamiQ cluster Vincent Guittot
2018-03-28  9:12 ` Will Deacon
2018-03-28 14:02   ` Vincent Guittot
2018-03-29 12:53 ` Morten Rasmussen
2018-03-30 12:34   ` Vincent Guittot
2018-04-02 22:27     ` Valentin Schneider
2018-04-03 12:17       ` Vincent Guittot
2018-04-04 10:44         ` Valentin Schneider
2018-04-04 13:43           ` Vincent Guittot
2018-04-05 15:46             ` Morten Rasmussen
2018-04-05 16:22               ` Vincent Guittot
2018-04-06 12:58                 ` Morten Rasmussen
2018-04-09  7:34                   ` Vincent Guittot
2018-04-10 13:19                     ` Morten Rasmussen
2018-04-12 18:22                       ` Peter Zijlstra
2018-04-13  9:11                         ` Morten Rasmussen [this message]
2018-04-13 11:35                         ` Vincent Guittot
2018-04-13 20:12                   ` Joel Fernandes (Google)

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180413091136.GV4589@e105550-lin.cambridge.arm.com \
    --to=morten.rasmussen@arm.com \
    --cc=catalin.marinas@arm.com \
    --cc=chris.redpath@arm.com \
    --cc=dietmar.eggemann@arm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=peterz@infradead.org \
    --cc=valentin.schneider@arm.com \
    --cc=vincent.guittot@linaro.org \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).