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author | Daniel Lezcano <daniel.lezcano@linaro.org> | 2018-10-04 14:04:03 +0200 |
---|---|---|
committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2018-10-25 16:49:27 +0200 |
commit | a7fe5190c03f8137ef08db84a58dd4daf2c4785d (patch) | |
tree | f4c2935ca4ccb9bbdc113b3bc29bd85c02cd0159 /drivers/cpuidle | |
parent | sched: Factor out nr_iowait and nr_iowait_cpu (diff) | |
download | linux-a7fe5190c03f8137ef08db84a58dd4daf2c4785d.tar.xz linux-a7fe5190c03f8137ef08db84a58dd4daf2c4785d.zip |
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.c | 25 |
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; } |