IF YOU WOULD LIKE TO GET AN ACCOUNT, please write an
email to Administrator. User accounts are meant only to access repo
and report issues and/or generate pull requests.
This is a purpose-specific Git hosting for
BaseALT
projects. Thank you for your understanding!
Только зарегистрированные пользователи имеют доступ к сервису!
Для получения аккаунта, обратитесь к администратору.
Several parts of the kernel are already using the effective CPU
utilization (as seen by the scheduler) to get the current load on the
CPU, do the same here instead of depending on the idle time of the CPU,
which isn't that accurate comparatively.
This is also the right thing to do as it makes the cpufreq governor
(schedutil) align better with the cpufreq_cooling driver, as the power
requested by cpufreq_cooling governor will exactly match the next
frequency requested by the schedutil governor since they are both using
the same metric to calculate load.
This was tested on ARM Hikey6220 platform with hackbench, sysbench and
schbench. None of them showed any regression or significant
improvements. Schbench is the most important ones out of these as it
creates the scenario where the utilization numbers provide a better
estimate of the future.
Scenario 1: The CPUs were mostly idle in the previous polling window of
the IPA governor as the tasks were sleeping and here are the details
from traces (load is in %):
Old: thermal_power_cpu_get_power: cpus=00000000,000000ff freq=1200000 total_load=203 load={{0x35,0x1,0x0,0x31,0x0,0x0,0x64,0x0}} dynamic_power=1339
New: thermal_power_cpu_get_power: cpus=00000000,000000ff freq=1200000 total_load=600 load={{0x60,0x46,0x45,0x45,0x48,0x3b,0x61,0x44}} dynamic_power=3960
Here, the "Old" line gives the load and requested_power (dynamic_power
here) numbers calculated using the idle time based implementation, while
"New" is based on the CPU utilization from scheduler.
As can be clearly seen, the load and requested_power numbers are simply
incorrect in the idle time based approach and the numbers collected from
CPU's utilization are much closer to the reality.
Scenario 2: The CPUs were busy in the previous polling window of the IPA
governor:
Old: thermal_power_cpu_get_power: cpus=00000000,000000ff freq=1200000 total_load=800 load={{0x64,0x64,0x64,0x64,0x64,0x64,0x64,0x64}} dynamic_power=5280
New: thermal_power_cpu_get_power: cpus=00000000,000000ff freq=1200000 total_load=708 load={{0x4d,0x5c,0x5c,0x5b,0x5c,0x5c,0x51,0x5b}} dynamic_power=4672
As can be seen, the idle time based load is 100% for all the CPUs as it
took only the last window into account, but in reality the CPUs aren't
that loaded as shown by the utilization numbers.
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lkml.kernel.org/r/9c255c83d78d58451abc06848001faef94c87a12.1607400596.git.viresh.kumar@linaro.org
d1515851ca