Messages in this thread | | | Date | Thu, 25 Feb 2016 10:12:49 +0100 | From | Peter Zijlstra <> | Subject | Re: [RFC/RFT][PATCH v3 2/2] cpufreq: schedutil: Switching frequencies from interrupt context |
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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.
> > + if (diff >= best_diff) > > + continue; > > + > > + best_diff = diff; > > + next_perf_state = entry->driver_data; > > + next_freq = freq; > > + if (best_diff == 0) > > + goto found; > > + } > > + if (best_diff == UINT_MAX) > > + return CPUFREQ_ENTRY_INVALID; > > + > > + found: > > + perf = to_perf_data(data); > > + if (perf->state == next_perf_state) { > > + if (unlikely(data->resume)) > > + data->resume = 0; > > + else > > + return next_freq; > > + } > > + > > + data->cpu_freq_fast_write(perf->states[next_perf_state].control); > > + perf->state = next_perf_state; > > + return next_freq; > > +}
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