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cpufreq: schedutil: Don't set next_freq to UINT_MAX

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The schedutil driver sets sg_policy->next_freq to UINT_MAX on certain
occasions to discard the cached value of next freq:
- In sugov_start(), when the schedutil governor is started for a group
  of CPUs.
- And whenever we need to force a freq update before rate-limit
  duration, which happens when:
  - there is an update in cpufreq policy limits.
  - Or when the utilization of DL scheduling class increases.

In return, get_next_freq() doesn't return a cached next_freq value but
recalculates the next frequency instead.

But having special meaning for a particular value of frequency makes the
code less readable and error prone. We recently fixed a bug where the
UINT_MAX value was considered as valid frequency in
sugov_update_single().

All we need is a flag which can be used to discard the value of
sg_policy->next_freq and we already have need_freq_update for that. Lets
reuse it instead of setting next_freq to UINT_MAX.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Viresh Kumar 2018-05-09 16:05:24 +05:30 committed by Rafael J. Wysocki
parent 1b04722c3b
commit ecd2884291
1 changed files with 6 additions and 12 deletions
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18
kernel/sched/cpufreq_schedutil.c
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@ -95,15 +95,8 @@ static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
if (sg_policy->work_in_progress)
return false;
if (unlikely(sg_policy->need_freq_update)) {
sg_policy->need_freq_update = false;
/*
* This happens when limits change, so forget the previous
* next_freq value and force an update.
*/
sg_policy->next_freq = UINT_MAX;
if (unlikely(sg_policy->need_freq_update))
return true;
}
delta_ns = time - sg_policy->last_freq_update_time;
@ -165,8 +158,10 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
freq = (freq + (freq >> 2)) * util / max;
if (freq == sg_policy->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update)
return sg_policy->next_freq;
sg_policy->need_freq_update = false;
sg_policy->cached_raw_freq = freq;
return cpufreq_driver_resolve_freq(policy, freq);
}
@ -305,8 +300,7 @@ static void sugov_update_single(struct update_util_data *hook, u64 time,
* Do not reduce the frequency if the CPU has not been idle
* recently, as the reduction is likely to be premature then.
*/
if (busy && next_f < sg_policy->next_freq &&
sg_policy->next_freq != UINT_MAX) {
if (busy && next_f < sg_policy->next_freq) {
next_f = sg_policy->next_freq;
/* Reset cached freq as next_freq has changed */
@ -654,7 +648,7 @@ static int sugov_start(struct cpufreq_policy *policy)
sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
sg_policy->last_freq_update_time = 0;
sg_policy->next_freq = UINT_MAX;
sg_policy->next_freq = 0;
sg_policy->work_in_progress = false;
sg_policy->need_freq_update = false;
sg_policy->cached_raw_freq = 0;