| Message ID | 2897534536b2506cbdbd5f8ace6f1c2dcdad189d.1510152832.git.viresh.kumar@linaro.org |
|---|---|
| State | Accepted |
| Commit | 07458f6a5171d97511dfbdf6ce549ed2ca0280c7 |
| Headers | show |
| Series | schedutil: Reset cached freq if it is not in sync with next_freq | expand |
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index ba0da243fdd8..2f52ec0f1539 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -282,8 +282,12 @@ 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); }
'cached_raw_freq' is used to get the next frequency quickly but should always be in sync with sg_policy->next_freq. There is a case 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 see the CPU wasn't idle recently and choose to keep the next freq as 1.2 GHz. - Now we have cached_raw_freq is 780 MHz and sg_policy->next_freq is 1.2 GHz. - Now if the utilization doesn't change in then next request, then the next target frequency will still be 780 MHz and it will match with cached_raw_freq. But we will choose 1.2 GHz instead of 800 MHz here. Change-Id: I71bd31a1b59d27c26c0b4885301e4ba6155c2c51 Cc: <stable@vger.kernel.org> # 4.12 Fixes: b7eaf1aab9f8 ("cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely") Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- kernel/sched/cpufreq_schedutil.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) -- 2.15.0.rc1.236.g92ea95045093