Re: [RFC/RFT][PATCH v3 2/2] cpufreq: schedutil: Switching frequencies from interrupt context

[Rafael J. Wysocki]

On Thursday, February 25, 2016 10:12:49 AM Peter Zijlstra wrote:
> On Thu, Feb 25, 2016 at 10:08:40AM +0100, Peter Zijlstra wrote:
> > On Thu, Feb 25, 2016 at 12:30:43AM +0100, Rafael J. Wysocki wrote:
> > > +unsigned int acpi_cpufreq_fast_switch(struct cpufreq_policy *policy,
> > > +				      unsigned int target_freq)
> > > +{
> > > +	struct acpi_cpufreq_data *data = policy->driver_data;
> > > +	struct cpufreq_frequency_table *entry;
> > > +	struct acpi_processor_performance *perf;
> > > +	unsigned int uninitialized_var(next_perf_state);
> > > +	unsigned int uninitialized_var(next_freq);
> > > +	unsigned int best_diff;
> > > +
> > > +	for (entry = data->freq_table, best_diff = UINT_MAX;
> > > +	     entry->frequency != CPUFREQ_TABLE_END; entry++) {
> > > +		unsigned int diff, freq = entry->frequency;
> > > +
> > > +		if (freq == CPUFREQ_ENTRY_INVALID)
> > > +			continue;
> > > +
> > > +		diff = abs(freq - target_freq);
> > 
> > Why would you consider frequencies that are below where you want to be?
> 
> Also, if you look for the first largest freq (which would make most
> sense I think) and this table is sorted, you can do a binary search.
> 
> Then again, not sure the table is big enough to make that worth it.

Yeah, that was my thought too.