linux-kernel - Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data structures

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Message-ID: <20150812172318.GX16853@twins.programming.kicks-ass.net>
Date:	Wed, 12 Aug 2015 19:23:18 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dietmar Eggemann <dietmar.eggemann@....com>
Cc:	Morten Rasmussen <Morten.Rasmussen@....com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
	"yuyang.du@...el.com" <yuyang.du@...el.com>,
	"mturquette@...libre.com" <mturquette@...libre.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>,
	Juri Lelli <Juri.Lelli@....com>,
	"sgurrappadi@...dia.com" <sgurrappadi@...dia.com>,
	"pang.xunlei@....com.cn" <pang.xunlei@....com.cn>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [RFCv5 PATCH 16/46] sched: Allocate and initialize energy data
 structures

On Wed, Aug 12, 2015 at 06:09:59PM +0100, Dietmar Eggemann wrote:
> > One more question, if fn() returns a full structure, why are we
> > allocating and copying the thing? Its all const read only data, right?
> > 
> 
> Yeah, that's not strictly necessary. I could get rid of all the
> allocation/copying/ and freeing code and just simply set sd->groups->sge
> = fn(cpu) in init_sched_energy(). Plus delete the atomic_t ref in struct
> sched_group_energy.
> 
> In this case, should I still keep the check_sched_energy_data() function
> to verify that the scheduler got valid data via the struct
> sched_domain_topology_level table from the arch, i.e. to make sure that
> the per-cpu provided sd energy data is consistent for all cpus within
> the sched group cpumask?

Oh yes very much. We want sanity checking of the data handed.
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