linux-kernel - Re: [PATCH v5 4/9] x86: Enable Intel Turbo Boost Max Technology 3.0

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Date:   Wed, 05 Oct 2016 09:05:20 -0700
From:   Tim Chen <tim.c.chen@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     rjw@...ysocki.net, mingo@...hat.com, bp@...e.de, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, peterz@...radead.org, jolsa@...hat.com
Subject: Re: [PATCH v5 4/9] x86: Enable Intel Turbo Boost Max Technology 3.0

On Wed, 2016-10-05 at 16:23 +0200, Thomas Gleixner wrote:
> On Sat, 1 Oct 2016, Srinivas Pandruvada wrote:
> > 
> > +void sched_set_itmt_support(bool itmt_supported)
> > +{
> > +	mutex_lock(&itmt_update_mutex);
> > +
> > +	if (itmt_supported != sched_itmt_capable)
> > +		sched_itmt_capable = itmt_supported;
> Yikes. What is this conditional for? The only value it has is to confuse
> the reader.

Will remove the check.

> 
> > 
> > +
> > +	mutex_unlock(&itmt_update_mutex);
> > +}
> > +
> > +DEFINE_PER_CPU_READ_MOSTLY(int, sched_core_priority);
> Darn. Do not stick variable definitiions in the middle of the code and
> especially not glued to the function w/o a newline in between. Move it to
> the top of the file.

Will move to top of file.

> 
> > 
> > +int arch_asym_cpu_priority(int cpu)
> > +{
> > +	return per_cpu(sched_core_priority, cpu);
> > +}
> 
> > 
> > +void sched_set_itmt_core_prio(int prio, int core_cpu)
> > +{
> > +	int cpu, i = 1;
> > +
> > +	for_each_cpu(cpu, topology_sibling_cpumask(core_cpu)) {
> > +		int smt_prio;
> > +
> > +		/*
> > +		 * Ensure that the siblings are moved to the end
> > +		 * of the priority chain and only used when
> > +		 * all other high priority cpus are out of capacity.
> > +		 */
> > +		smt_prio = prio * smp_num_siblings / i;
> > +		i++;
> Your code ordering is really random. What has this i++ to do with the
> store? Nothing. It just makes reading the code harder. Just move it below
> the store.

Will move it to the end of for loop.

> 
> > 
> > +		per_cpu(sched_core_priority, cpu) = smt_prio;

Thanks.

Tim