linux-kernel - Re: [RFC][PATCH 8/9] sched: power: Add initial frequency scaling support to power scheduler

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Message-ID: <20130712130601.GD28271@arm.com>
Date:	Fri, 12 Jul 2013 14:06:01 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Morten Rasmussen <Morten.Rasmussen@....com>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	"alex.shi@...el.com" <alex.shi@...el.com>,
	"efault@....de" <efault@....de>, "pjt@...gle.com" <pjt@...gle.com>,
	"len.brown@...el.com" <len.brown@...el.com>,
	"corbet@....net" <corbet@....net>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>
Subject: Re: [RFC][PATCH 8/9] sched: power: Add initial frequency scaling
 support to power scheduler

On Fri, Jul 12, 2013 at 01:51:13PM +0100, Morten Rasmussen wrote:
> On Wed, Jul 10, 2013 at 02:10:59PM +0100, Arjan van de Ven wrote:
> > On 7/9/2013 8:55 AM, Morten Rasmussen wrote:
> > > Extends the power scheduler capacity management algorithm to handle
> > > frequency scaling and provide basic frequency/P-state selection hints
> > > to the power driver.
> > >
> > > Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
> > > CC: Ingo Molnar <mingo@...nel.org>
> > > CC: Peter Zijlstra <peterz@...radead.org>
> > > CC: Catalin Marinas <catalin.marinas@....com>
> > > ---
> > >   kernel/sched/power.c |   33 ++++++++++++++++++++++++++++-----
> > >   1 file changed, 28 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/kernel/sched/power.c b/kernel/sched/power.c
> > > index 9e44c0e..5fc32b0 100644
> > > --- a/kernel/sched/power.c
> > > +++ b/kernel/sched/power.c
> > > @@ -21,6 +21,8 @@
> > >
> > >   #define INTERVAL 5 /* ms */
> > >   #define CPU_FULL 90 /* Busy %-age - TODO: Make tunable */
> > > +#define CPU_TARGET 80 /* Target busy %-age - TODO: Make tunable */
> > > +#define CPU_EMPTY 5 /* Idle noise %-age - TODO: Make tunable */
> > >
> > 
> > to be honest, this is the policy part that really should be in the hardware specific driver
> > and not in the scheduler.
> > (even if said driver is sort of a "generic library" kind of thing)
> 
> I agree that the values should be set by a hardware specific power
> driver. Or do you mean that algorithms using this sort of values should
> be in the driver?

I think for flexibility we could place the default algorithm in a
library and it would be used by the cpufreq power driver wrapper or
directly by a new power driver. The intel_pstate.c driver could be
allowed to do smarter things.

-- 
Catalin
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