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authorViresh Kumar <viresh.kumar@linaro.org>2017-11-08 20:23:55 +0530
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-11-08 23:59:33 +0100
commit07458f6a5171d97511dfbdf6ce549ed2ca0280c7 (patch)
tree5c55fa92fc2e2971e2654839c3df1535ed96c40b /kernel/sched
parentd62d813c0d714a2d0aaf3d796a7a51ae60bf5470 (diff)
downloadlinux-07458f6a5171d97511dfbdf6ce549ed2ca0280c7.tar.bz2
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 <viresh.kumar@linaro.org> Cc: 4.12+ <stable@vger.kernel.org> # 4.12+ Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/cpufreq_schedutil.c6
1 files changed, 5 insertions, 1 deletions
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);
}