From 07458f6a5171d97511dfbdf6ce549ed2ca0280c7 Mon Sep 17 00:00:00 2001 From: Viresh Kumar Date: Wed, 8 Nov 2017 20:23:55 +0530 Subject: [PATCH] cpufreq: schedutil: Reset cached_raw_freq when not in sync with next_freq '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. Fixes: b7eaf1aab9f8 (cpufreq: schedutil: Avoid reducing frequency of busy CPUs prematurely) Signed-off-by: Viresh Kumar Cc: 4.12+ # 4.12+ Signed-off-by: Rafael J. Wysocki --- kernel/sched/cpufreq_schedutil.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) 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); }