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

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Message-ID: <20160119142933.GF8573@e106622-lin>
Date:	Tue, 19 Jan 2016 14:29:33 +0000
From:	Juri Lelli <juri.lelli@....com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	Vincent Guittot <vincent.guittot@...aro.org>,
	Mark Rutland <mark.rutland@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mark Brown <broonie@...nel.org>,
	Will Deacon <will.deacon@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Steve Muckle <steve.muckle@...aro.org>,
	Sudeep Holla <sudeep.holla@....com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	LAK <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v2 0/4] CPUs capacity information for heterogeneous
 systems

On 19/01/16 11:23, Juri Lelli wrote:
> Hi Catalin,
> 
> On 19/01/16 10:59, Catalin Marinas wrote:
> > On Mon, Jan 18, 2016 at 05:42:58PM +0100, Vincent Guittot wrote:
> > > On 18 January 2016 at 17:30, Juri Lelli <juri.lelli@....com> wrote:
> > > > On 18/01/16 17:13, Vincent Guittot wrote:
> > > >> On 18 January 2016 at 16:13, Juri Lelli <juri.lelli@....com> wrote:
> > > >> > On 15/01/16 11:50, Steve Muckle wrote:
> > > >> >> On 01/08/2016 06:09 AM, Juri Lelli wrote:

[...]

> > 
> > Two questions:
> > 
> > 1. How is the boot time affected by the benchmark?
> > 2. How is the boot time affected by considering all the CPUs the same?
> > 
> > My preference is for DT and sysfs (especially useful for
> > development/tuning) but I'm not opposed to a boot-time benchmark if
> > people insist on it. If the answer to point 2 is "insignificant", we
> > could as well defer the capacity setting to user space (sysfs).
> > 
> 
> Given that we are not targeting boot time with this, but rather better
> performance afterwards, I don't expect significant differences; but,
> I'll get numbers :).
> 

I've got some boot time numbers on TC2 and Juno based on timestamps.
They are of course not accurate and maybe not so representative of
products, but I guess still ballpark right.

I'm generally seeing ~1sec increase in boot time for 1 and practically
no difference for 2 (even after having added patches that provide
runtime performance improvements).

Best,

- Juri