All of lore.kernel.org
 help / color / mirror / Atom feed
From: Juri Lelli <juri.lelli@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, vincent.guittot@linaro.org,
	robh+dt@kernel.org, mark.rutland@arm.com, linux@arm.linux.org.uk,
	sudeep.holla@arm.com, lorenzo.pieralisi@arm.com,
	catalin.marinas@arm.com, will.deacon@arm.com,
	morten.rasmussen@arm.com, dietmar.eggemann@arm.com
Subject: Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems
Date: Wed, 20 Jan 2016 10:25:48 +0000	[thread overview]
Message-ID: <20160120102548.GO8573@e106622-lin> (raw)
In-Reply-To: <20160119175038.GS6588@sirena.org.uk>

On 19/01/16 17:50, Mark Brown wrote:
> On Tue, Jan 19, 2016 at 04:05:51PM +0100, Peter Zijlstra wrote:
> > On Fri, Jan 08, 2016 at 02:09:28PM +0000, Juri Lelli wrote:
> 
> > >     cons: - not easy to come up with a clean solution, as it seems interaction
> > >             with several subsystems (e.g., cpufreq) is required
> > >           - not easy to agree upon a single benchmark (that has to be both
> > >             representative and simple enough to run at boot)
> > >           - numbers might (and do) vary from boot to boot
> 
> > This last point is a total pain for benchmarking, it means nothing is
> > every reproducible.
> 
> > Therefore, I would always augment the above (2) with the below (3), such
> > that you can overwrite the results with a known stable set of numbers:
> 
> The suggestion when the previous version was being discussed was that
> there are supposed to be some other knobs one uses for tuning and one
> was never supposed to use these numbers.

Right, DT solution might live without a sysfs interface, as you want to
use those other knobs for runtime tuning. Dynamic solution instead, and
I think this is what Peter was also pointing out, will most probably
require a sysfs interface for cases in which variation of default values
from boot to boot is not acceptable.

WARNING: multiple messages have this Message-ID (diff)
From: juri.lelli@arm.com (Juri Lelli)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems
Date: Wed, 20 Jan 2016 10:25:48 +0000	[thread overview]
Message-ID: <20160120102548.GO8573@e106622-lin> (raw)
In-Reply-To: <20160119175038.GS6588@sirena.org.uk>

On 19/01/16 17:50, Mark Brown wrote:
> On Tue, Jan 19, 2016 at 04:05:51PM +0100, Peter Zijlstra wrote:
> > On Fri, Jan 08, 2016 at 02:09:28PM +0000, Juri Lelli wrote:
> 
> > >     cons: - not easy to come up with a clean solution, as it seems interaction
> > >             with several subsystems (e.g., cpufreq) is required
> > >           - not easy to agree upon a single benchmark (that has to be both
> > >             representative and simple enough to run at boot)
> > >           - numbers might (and do) vary from boot to boot
> 
> > This last point is a total pain for benchmarking, it means nothing is
> > every reproducible.
> 
> > Therefore, I would always augment the above (2) with the below (3), such
> > that you can overwrite the results with a known stable set of numbers:
> 
> The suggestion when the previous version was being discussed was that
> there are supposed to be some other knobs one uses for tuning and one
> was never supposed to use these numbers.

Right, DT solution might live without a sysfs interface, as you want to
use those other knobs for runtime tuning. Dynamic solution instead, and
I think this is what Peter was also pointing out, will most probably
require a sysfs interface for cases in which variation of default values
from boot to boot is not acceptable.

  reply	other threads:[~2016-01-20 10:25 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-08 14:09 [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems Juri Lelli
2016-01-08 14:09 ` Juri Lelli
2016-01-08 14:09 ` [RFC PATCH v2 1/4] ARM: initialize cpu_scale to its default Juri Lelli
2016-01-08 14:09   ` Juri Lelli
2016-01-08 14:09   ` Juri Lelli
2016-01-08 14:09 ` [RFC PATCH v2 2/4] drivers/cpufreq: implement init_cpu_capacity_default() Juri Lelli
2016-01-08 14:09   ` Juri Lelli
2016-01-08 14:09 ` [RFC PATCH v2 3/4] arm: Enable dynamic CPU capacity initialization Juri Lelli
2016-01-08 14:09   ` Juri Lelli
2016-01-08 14:09 ` [RFC PATCH v2 4/4] arm64: " Juri Lelli
2016-01-08 14:09   ` Juri Lelli
2016-01-15 18:01 ` [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems Mark Brown
2016-01-15 18:01   ` Mark Brown
2016-01-18 15:01   ` Juri Lelli
2016-01-18 15:01     ` Juri Lelli
2016-01-15 19:50 ` Steve Muckle
2016-01-15 19:50   ` Steve Muckle
2016-01-18 15:13   ` Juri Lelli
2016-01-18 15:13     ` Juri Lelli
2016-01-18 16:13     ` Vincent Guittot
2016-01-18 16:13       ` Vincent Guittot
2016-01-18 16:30       ` Juri Lelli
2016-01-18 16:30         ` Juri Lelli
2016-01-18 16:42         ` Vincent Guittot
2016-01-18 16:42           ` Vincent Guittot
2016-01-18 17:08           ` Juri Lelli
2016-01-18 17:08             ` Juri Lelli
2016-01-18 17:23             ` Vincent Guittot
2016-01-18 17:23               ` Vincent Guittot
2016-01-19 10:59           ` Catalin Marinas
2016-01-19 10:59             ` Catalin Marinas
2016-01-19 11:23             ` Juri Lelli
2016-01-19 11:23               ` Juri Lelli
2016-01-19 14:29               ` Juri Lelli
2016-01-19 14:29                 ` Juri Lelli
2016-01-19 19:48                 ` Steve Muckle
2016-01-19 19:48                   ` Steve Muckle
2016-01-19 21:10                   ` Mark Brown
2016-01-19 21:10                     ` Mark Brown
2016-01-20 10:22                     ` Juri Lelli
2016-01-20 10:22                       ` Juri Lelli
2016-01-18 19:25     ` Steve Muckle
2016-01-18 19:25       ` Steve Muckle
2016-01-19 15:05 ` Peter Zijlstra
2016-01-19 15:05   ` Peter Zijlstra
2016-01-19 17:50   ` Mark Brown
2016-01-19 17:50     ` Mark Brown
2016-01-20 10:25     ` Juri Lelli [this message]
2016-01-20 10:25       ` Juri Lelli

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=20160120102548.GO8573@e106622-lin \
    --to=juri.lelli@arm.com \
    --cc=broonie@kernel.org \
    --cc=catalin.marinas@arm.com \
    --cc=dietmar.eggemann@arm.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-pm@vger.kernel.org \
    --cc=linux@arm.linux.org.uk \
    --cc=lorenzo.pieralisi@arm.com \
    --cc=mark.rutland@arm.com \
    --cc=morten.rasmussen@arm.com \
    --cc=peterz@infradead.org \
    --cc=robh+dt@kernel.org \
    --cc=sudeep.holla@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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.