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authorDaniel Lezcano <daniel.lezcano@linaro.org>2018-10-04 14:04:03 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2018-10-25 16:49:27 +0200
commita7fe5190c03f8137ef08db84a58dd4daf2c4785d (patch)
treef4c2935ca4ccb9bbdc113b3bc29bd85c02cd0159 /drivers/cpuidle
parent145d952a29320dea883246bcb24ba1da7ac4bb7f (diff)
downloadlinux-a7fe5190c03f8137ef08db84a58dd4daf2c4785d.tar.bz2
cpuidle: menu: Remove get_loadavg() from the performance multiplier
The function get_loadavg() returns almost always zero. To be more precise, statistically speaking for a total of 1023379 times passing in the function, the load is equal to zero 1020728 times, greater than 100, 610 times, the remaining is between 0 and 5. In 2011, the get_loadavg() was removed from the Android tree because of the above [1]. At this time, the load was: unsigned long this_cpu_load(void) { struct rq *this = this_rq(); return this->cpu_load[0]; } In 2014, the code was changed by commit 372ba8cb46b2 (cpuidle: menu: Lookup CPU runqueues less) and the load is: void get_iowait_load(unsigned long *nr_waiters, unsigned long *load) { struct rq *rq = this_rq(); *nr_waiters = atomic_read(&rq->nr_iowait); *load = rq->load.weight; } with the same result. Both measurements show using the load in this code path does no matter anymore. Removing it. [1] https://android.googlesource.com/kernel/common/+/4dedd9f124703207895777ac6e91dacde0f7cc17 Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Acked-by: Mel Gorman <mgorman@suse.de> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/governors/menu.c25
1 files changed, 6 insertions, 19 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 575a68f31761..76df4f947f07 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -134,11 +134,6 @@ struct menu_device {
#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
-static inline int get_loadavg(unsigned long load)
-{
- return LOAD_INT(load) * 10 + LOAD_FRAC(load) / 10;
-}
-
static inline int which_bucket(unsigned int duration, unsigned long nr_iowaiters)
{
int bucket = 0;
@@ -172,18 +167,10 @@ static inline int which_bucket(unsigned int duration, unsigned long nr_iowaiters
* to be, the higher this multiplier, and thus the higher
* the barrier to go to an expensive C state.
*/
-static inline int performance_multiplier(unsigned long nr_iowaiters, unsigned long load)
+static inline int performance_multiplier(unsigned long nr_iowaiters)
{
- int mult = 1;
-
- /* for higher loadavg, we are more reluctant */
-
- mult += 2 * get_loadavg(load);
-
- /* for IO wait tasks (per cpu!) we add 5x each */
- mult += 10 * nr_iowaiters;
-
- return mult;
+ /* for IO wait tasks (per cpu!) we add 10x each */
+ return 1 + 10 * nr_iowaiters;
}
static DEFINE_PER_CPU(struct menu_device, menu_devices);
@@ -301,7 +288,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
int idx;
unsigned int interactivity_req;
unsigned int predicted_us;
- unsigned long nr_iowaiters, cpu_load;
+ unsigned long nr_iowaiters;
ktime_t delta_next;
if (data->needs_update) {
@@ -312,7 +299,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
/* determine the expected residency time, round up */
data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length(&delta_next));
- get_iowait_load(&nr_iowaiters, &cpu_load);
+ nr_iowaiters = nr_iowait_cpu(dev->cpu);
data->bucket = which_bucket(data->next_timer_us, nr_iowaiters);
if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
@@ -356,7 +343,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
* Use the performance multiplier and the user-configurable
* latency_req to determine the maximum exit latency.
*/
- interactivity_req = predicted_us / performance_multiplier(nr_iowaiters, cpu_load);
+ interactivity_req = predicted_us / performance_multiplier(nr_iowaiters);
if (latency_req > interactivity_req)
latency_req = interactivity_req;
}