From: Mark Brown <broonie@kernel.org>
To: Juri Lelli <juri.lelli@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, peterz@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: Fri, 15 Jan 2016 18:01:07 +0000 [thread overview]
Message-ID: <20160115180107.GC6588@sirena.org.uk> (raw)
In-Reply-To: <1452262172-31861-1-git-send-email-juri.lelli@arm.com>
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On Fri, Jan 08, 2016 at 02:09:28PM +0000, Juri Lelli wrote:
> Second version of this RFC proposes an alternative solution (w.r.t. v1) to the
> problem of how do we init CPUs original capacity: we run a bogus benchmark (for
> this RFC I simple stole int_sqrt from lib/ and I run that in a loop to perform
> some integer computation, I'm sure there are better benchmarks around) on the
> first cpu of each frequency domain (assuming no u-arch differences inside
> domains), measure time to complete a fixed number of iterations and then
> normalize results to SCHED_CAPACITY_SCALE (1024). I didn't spend much time in
> polishing this up or thinking about a better benchmark, as this is an RFC and
> I'd like discussion happening before we make this solution better
> working/looking. However, surprisingly, results are not that bad already:
This approach looks good to me - certainly vastly preferable to putting
the numbers into DT.
> 2. Dynamic profiling at boot (v2)
>
> pros: - does not require a standardized definition of capacity
> - cannot be incorrectly tuned (once benchmark is fixed)
> - does not require user/integrator work
> cons: - not easy to come up with a clean solution, as it seems interaction
> with several subsystems (e.g., cpufreq) is required
This actually seems to be pretty clean.
> - 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 does come back to the question of how accurate the numbers need to
be - is "good enough" fine?
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From: broonie@kernel.org (Mark Brown)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems
Date: Fri, 15 Jan 2016 18:01:07 +0000 [thread overview]
Message-ID: <20160115180107.GC6588@sirena.org.uk> (raw)
In-Reply-To: <1452262172-31861-1-git-send-email-juri.lelli@arm.com>
On Fri, Jan 08, 2016 at 02:09:28PM +0000, Juri Lelli wrote:
> Second version of this RFC proposes an alternative solution (w.r.t. v1) to the
> problem of how do we init CPUs original capacity: we run a bogus benchmark (for
> this RFC I simple stole int_sqrt from lib/ and I run that in a loop to perform
> some integer computation, I'm sure there are better benchmarks around) on the
> first cpu of each frequency domain (assuming no u-arch differences inside
> domains), measure time to complete a fixed number of iterations and then
> normalize results to SCHED_CAPACITY_SCALE (1024). I didn't spend much time in
> polishing this up or thinking about a better benchmark, as this is an RFC and
> I'd like discussion happening before we make this solution better
> working/looking. However, surprisingly, results are not that bad already:
This approach looks good to me - certainly vastly preferable to putting
the numbers into DT.
> 2. Dynamic profiling at boot (v2)
>
> pros: - does not require a standardized definition of capacity
> - cannot be incorrectly tuned (once benchmark is fixed)
> - does not require user/integrator work
> cons: - not easy to come up with a clean solution, as it seems interaction
> with several subsystems (e.g., cpufreq) is required
This actually seems to be pretty clean.
> - 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 does come back to the question of how accurate the numbers need to
be - is "good enough" fine?
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next prev parent reply other threads:[~2016-01-15 18:01 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 ` Mark Brown [this message]
2016-01-15 18:01 ` [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous systems 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
2016-01-20 10:25 ` Juri Lelli
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