Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems

From	Juri Lelli <juri.lelli@arm.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems
Date	2016-01-20 11:30 +0100
Message-ID	<qSYbw-51L-7@gated-at.bofh.it> (permalink)
References	<qOFTS-7OQ-53@gated-at.bofh.it> <qSG4V-18j-13@gated-at.bofh.it> <qSIJt-2KR-27@gated-at.bofh.it>
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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.

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Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous  systems Peter Zijlstra <peterz@infradead.org> - 2016-01-19 16:10 +0100
  Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous  systems Mark Brown <broonie@kernel.org> - 2016-01-19 19:00 +0100
    Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous  systems Juri Lelli <juri.lelli@arm.com> - 2016-01-20 11:30 +0100

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