Messages in this thread | | | From | Steve Muckle <> | Date | Thu, 19 May 2016 12:35:47 -0700 | Subject | Re: [PATCH 4/5] cpufreq: schedutil: map raw required frequency to CPU-supported frequency |
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On Thu, May 19, 2016 at 01:37:40AM +0200, Rafael J. Wysocki wrote: > On Mon, May 9, 2016 at 11:20 PM, Steve Muckle <steve.muckle@linaro.org> wrote: > > The mechanisms for remote CPU updates and slow-path frequency > > transitions are relatively expensive - the former is an IPI while the > > latter requires waking up a thread to do work. These activities should > > be avoided if they are not necessary. To that end, calculate the > > actual target-supported frequency required by the new utilization > > value in schedutil. If it is the same as the previously requested > > frequency then there is no need to continue with the update. > > Unless the max/min limits changed in the meantime, right?
Right, I'll amend the commit text. The functionality is correct AFAICS.
> > > > Signed-off-by: Steve Muckle <smuckle@linaro.org> > > --- > > kernel/sched/cpufreq_schedutil.c | 14 +++++++++++++- > > 1 file changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c > > index 6cb2ecc204ec..e185075fcb5c 100644 > > --- a/kernel/sched/cpufreq_schedutil.c > > +++ b/kernel/sched/cpufreq_schedutil.c > > @@ -153,14 +153,26 @@ static void sugov_update_commit(struct sugov_cpu *sg_cpu, int cpu, u64 time, > > * next_freq = C * curr_freq * util_raw / max > > * > > * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8. > > + * > > + * The lowest target-supported frequency which is equal or greater than the raw > > + * next_freq (as calculated above) is returned, or the CPU's max_freq if such > > + * a target-supported frequency does not exist. > > */ > > static unsigned int get_next_freq(struct cpufreq_policy *policy, > > unsigned long util, unsigned long max) > > { > > + struct cpufreq_frequency_table *entry; > > unsigned int freq = arch_scale_freq_invariant() ? > > policy->cpuinfo.max_freq : policy->cur; > > + unsigned int target_freq = UINT_MAX; > > + > > + freq = (freq + (freq >> 2)) * util / max; > > + > > + cpufreq_for_each_valid_entry(entry, policy->freq_table) > > + if (entry->frequency >= freq && entry->frequency < target_freq) > > + target_freq = entry->frequency; > > Please don't assume that every driver will have a frequency table. > That may not be the case in the future (and I'm not even sure about > the existing CPPC driver for that matter).
For platforms without a frequency table I guess we can just continue with the current behavior, passing in the raw calculated frequency. I'll make this change.
At some point I imagine those platforms will want to somehow achieve similar behavior to avoid very small transitions that do not result in real benefit. Maybe some sort of threshold % in the schedutil down the road.
thanks, Steve
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