cpufreq: Break out early when frequency equals target_freq

PATCH RESEND In review Stratos Karafotis 2 participants 2 messages May 14, 2014 – May 15, 2014 CPU frequency scaling framework

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Stratos Karafotis

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2014-05-14 18:05 UTC #0 lore raw

PATCH RESEND 1/1 cpufreq: Break out early when frequency equals target_freq

Many drivers keep frequencies in frequency table in ascending or descending order. When governor tries to change to policy->min or policy->max respectively then the cpufreq_frequency_table_target could return on first iteration. This will save some iteration cycles.

So, break out early when a frequency in cpufreq_frequency_table equals to target one.

Testing this during kernel compilation using ondemand governor with a frequency table in ascending order, the cpufreq_frequency_table_target returned early on the first iteration at about 30% of times called.

Signed-off-by Stratos Karafotis <[email protected]>

---
 drivers/cpufreq/freq_table.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

drivers/cpufreq/freq_table.c +6 -2

index 8e518c6..1632981 100644
@@ -137,9 +137,13 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 		i = pos - table;
 		if ((freq < policy->min) || (freq > policy->max))
 			continue;
+		if (freq == target_freq) {
+			optimal.driver_data = i;
+			break;
+		}
 		switch (relation) {
 		case CPUFREQ_RELATION_H:
-			if (freq <= target_freq) {
+			if (freq < target_freq) {
 				if (freq >= optimal.frequency) {
 					optimal.frequency = freq;
 					optimal.driver_data = i;

@@ -152,7 +156,7 @@ int cpufreq_frequency_table_target(struct cpufreq_policy *policy,
 			}
 			break;
 		case CPUFREQ_RELATION_L:
-			if (freq >= target_freq) {
+			if (freq > target_freq) {
 				if (freq <= optimal.frequency) {
 					optimal.frequency = freq;
 					optimal.driver_data = i;

Signature · 1 line

1.9.0

Viresh Kumar

maintainer Acked-by on v1 1/1

2014-05-15 04:39 UTC #1 lore raw

Quoted 13 lines · Stratos Karafotis

Many drivers keep frequencies in frequency table in ascending or descending order. When governor tries to change to policy->min or policy->max respectively then the cpufreq_frequency_table_target could return on first iteration. This will save some iteration cycles.
So, break out early when a frequency in cpufreq_frequency_table equals to target one.
Testing this during kernel compilation using ondemand governor with a frequency table in ascending order, the cpufreq_frequency_table_target returned early on the first iteration at about 30% of times called.

Quoted 4 lines

Signed-off-by Stratos Karafotis <[email protected]>
---
 drivers/cpufreq/freq_table.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

Acked-by Viresh Kumar <[email protected]>