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BACKPORT: schedutil: Reset cached freq if it is not in sync with next_freq

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'cached_raw_freq' is used to get the next frequency quickly but should
always be in sync with sg_policy->next_freq. There are cases where it is
not and in such cases it should be reset to avoid switching to incorrect
frequencies.

Consider this case for example:
- policy->cur is 1.2 GHz (Max)
- New request comes for 780 MHz and we store that in cached_raw_freq.
- Based on 780 MHz, we calculate the effective frequency as 800 MHz.
- We then decide not to update the frequency as
  sugov_up_down_rate_limit() return true.
- Here cached_raw_freq is 780 MHz and sg_policy->next_freq is 1.2 GHz.
- Now if the utilization doesn't change in next request, then the next
  target frequency will still be 780 MHz and it will match with
  cached_raw_freq and so we will directly return 1.2 GHz instead of 800
  MHz.

BACKPORT of upstream commit 07458f6a51 ("cpufreq: schedutil: Reset
cached_raw_freq when not in sync with next_freq").

This also updates sugov_update_commit() for handling up/down tunables, which
aren't present in mainline.

Change-Id: I70bca2c5dfdb545a0471d1c9e4c5addb30ab5494
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
This commit is contained in:
Viresh Kumar
2017-11-08 19:47:36 +05:30
committed by Amit Pundir
parent 63e2298591
commit 56c4ae908c
1 changed files with 9 additions and 2 deletions
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11
kernel/sched/cpufreq_schedutil.c
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@@ -130,8 +130,11 @@ static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
{
struct cpufreq_policy *policy = sg_policy->policy;
if (sugov_up_down_rate_limit(sg_policy, time, next_freq))
if (sugov_up_down_rate_limit(sg_policy, time, next_freq)) {
/* Reset cached freq as next_freq isn't changed */
sg_policy->cached_raw_freq = 0;
return;
}
if (sg_policy->next_freq == next_freq)
return;
@@ -317,8 +320,12 @@ 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)
if (busy && next_f < sg_policy->next_freq) {
next_f = sg_policy->next_freq;
/* Reset cached freq as next_freq has changed */
sg_policy->cached_raw_freq = 0;
}
}
sugov_update_commit(sg_policy, time, next_f);
}