linux-kernel - Re: [RFC PATCH v4 03/12] PM: Introduce an Energy Model management framework

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: <20180705150629.GP2458@hirez.programming.kicks-ass.net>
Date:   Thu, 5 Jul 2018 17:06:29 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Quentin Perret <quentin.perret@....com>
Cc:     rjw@...ysocki.net, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, gregkh@...uxfoundation.org,
        mingo@...hat.com, dietmar.eggemann@....com,
        morten.rasmussen@....com, chris.redpath@....com,
        patrick.bellasi@....com, valentin.schneider@....com,
        vincent.guittot@...aro.org, thara.gopinath@...aro.org,
        viresh.kumar@...aro.org, tkjos@...gle.com, joel@...lfernandes.org,
        smuckle@...gle.com, adharmap@...cinc.com, skannan@...cinc.com,
        pkondeti@...eaurora.org, juri.lelli@...hat.com,
        edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
        currojerez@...eup.net, javi.merino@...nel.org
Subject: Re: [RFC PATCH v4 03/12] PM: Introduce an Energy Model management
 framework

On Thu, Jun 28, 2018 at 12:40:34PM +0100, Quentin Perret wrote:
> +/* fd_update_cs_table() - Computes the capacity values of a cs_table
> + *
> + * This assumes a linear relation between capacity and frequency. As such,
> + * the capacity of a CPU at the n^th capacity state is computed as:
> + *           capactity(n) = max_capacity * freq(n) / freq_max
> + */

Broken comment style

> +static void fd_update_cs_table(struct em_cs_table *cs_table, int cpu)
> +{
> +	unsigned long cmax = arch_scale_cpu_capacity(NULL, cpu);
> +	int max_cap_state = cs_table->nr_cap_states - 1;
> +	unsigned long fmax = cs_table->state[max_cap_state].frequency;
> +	int i;
> +
> +	for (i = 0; i < cs_table->nr_cap_states; i++) {
> +		u64 cap = (u64)cmax * cs_table->state[i].frequency;
> +		do_div(cap, fmax);
> +		cs_table->state[i].capacity = (unsigned long)cap;

I prefer div64_*() over do_div(), the calling convention the latter
always confuses the heck out of me.

So this then becomes something like:

		cs_table->state[i].capacity =
			div64_u64(cmax * cs_table->state[i].frequency, fmax);

> +	}
> +}