linux-kernel - Re: [RFC PATCH 8/8] arm64: add sysfs cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20151211175445.GR5727@sirena.org.uk>
Date:	Fri, 11 Dec 2015 17:54:45 +0000
From:	Mark Brown <broonie@...nel.org>
To:	Juri Lelli <juri.lelli@....com>
Cc:	Dietmar Eggemann <dietmar.eggemann@....com>,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	peterz@...radead.org, vincent.guittot@...aro.org,
	robh+dt@...nel.org, mark.rutland@....com, linux@....linux.org.uk,
	sudeep.holla@....com, lorenzo.pieralisi@....com,
	catalin.marinas@....com, will.deacon@....com,
	morten.rasmussen@....com
Subject: Re: [RFC PATCH 8/8] arm64: add sysfs cpu_capacity attribute

On Thu, Dec 10, 2015 at 06:01:59PM +0000, Juri Lelli wrote:
> On 10/12/15 15:59, Mark Brown wrote:
> > On Thu, Dec 10, 2015 at 02:15:04PM +0000, Dietmar Eggemann wrote:
> > > On 23/11/15 14:28, Juri Lelli wrote:

> > > > The new attribute shows up as:

> > > >  /sys/devices/system/cpu/cpu*/cpu_capacity

> > > This sysfs interface is not really needed for arm or arm64. People can
> > > build the dt blob if they want to change the values. Less code to carry
> > > ... Let's focus on the core functionality, which is parsing cpu capacity
> > > from dt file to task scheduler for heterogeneous systems.

> > That does make the tuning process much more cumbersome - users have to
> > rebuild and reboot to tweak the numbers rather than just tweaking the
> > numbers and rerunning the benchmark (which seems like something people
> > would want to automate).

> IMHO, this is not a tuning interface. It is an alternative interface,
> w.r.t. DTs, that we could use to provide default capacity values to the
> kernel. I'm proposing both here as they make both sense to me. Then we
> might dedice for which one to go (or if we need some other way) or to
> keep both for flexibility.

Kind of repeating what I said in the other mail but I'd say that any
interface which provides a mechanism for setting a magic number that
influences system performance is providing tuning.  It's hard to see how
else to describe it to be honest.

Download attachment "signature.asc" of type "application/pgp-signature" (474 bytes)