cpuidle: menu: Remove get_loadavg() from the performance multiplier
authorDaniel Lezcano <daniel.lezcano@linaro.org>
Thu, 4 Oct 2018 12:04:03 +0000 (14:04 +0200)
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>
Thu, 25 Oct 2018 14:49:27 +0000 (16:49 +0200)
commita7fe5190c03f8137ef08db84a58dd4daf2c4785d
treef4c2935ca4ccb9bbdc113b3bc29bd85c02cd0159
parent145d952a29320dea883246bcb24ba1da7ac4bb7f
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>
drivers/cpuidle/governors/menu.c
include/linux/sched/stat.h
kernel/sched/core.c