linux-kernel - Re: [PATCH v2 3/3] PM / EM: Skip inefficient OPPs

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Message-ID: <20210525094601.GB369979@e124901.cambridge.arm.com>
Date:   Tue, 25 May 2021 10:46:01 +0100
From:   Vincent Donnefort <vincent.donnefort@....com>
To:     Quentin Perret <qperret@...gle.com>
Cc:     peterz@...radead.org, rjw@...ysocki.net, viresh.kumar@...aro.org,
        vincent.guittot@...aro.org, linux-kernel@...r.kernel.org,
        ionela.voinescu@....com, lukasz.luba@....com,
        dietmar.eggemann@....com
Subject: Re: [PATCH v2 3/3] PM / EM: Skip inefficient OPPs

On Tue, May 25, 2021 at 09:33:01AM +0000, Quentin Perret wrote:
> On Friday 21 May 2021 at 17:54:24 (+0100), Vincent Donnefort wrote:
> > @@ -161,6 +162,8 @@ static int em_create_perf_table(struct device *dev, struct em_perf_domain *pd,
> >  		table[i].cost = div64_u64(fmax * table[i].power,
> >  					  table[i].frequency);
> >  		if (table[i].cost >= prev_cost) {
> > +			table[i].flags = EM_PERF_STATE_INEFFICIENT;
> > +			pd->flags |= EM_PERF_DOMAIN_INEFFICIENCIES;
> 
> If we're looking for micro-optimizations, then perhaps you could store
> the index of the next efficient OPP (which would be 'i' if the current
> OPP is already efficient), so you can jump to it directly when doing the
> search.

Wouldn't add any new field compared to this version so yeah might be an
interesting improvement.

> 
> >  			dev_dbg(dev, "EM: OPP:%lu is inefficient\n",
> >  				table[i].frequency);
> >  		} else {