Re: [PATCH v10 0/2] power: introduce PM QoS interface

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 12 Sep 2024 10:38:10 +0800
Huisong Li <lihuisong@huawei.com> wrote:

> The deeper the idle state, the lower the power consumption, but the longer
> the resume time. Some service are delay sensitive and very except the low
> resume time, like interrupt packet receiving mode.
> 
> And the "/sys/devices/system/cpu/cpuX/power/pm_qos_resume_latency_us" sysfs
> interface is used to set and get the resume latency limit on the cpuX for
> userspace. Please see the description in kernel document[1].
> Each cpuidle governor in Linux select which idle state to enter based on
> this CPU resume latency in their idle task.
> 
> The per-CPU PM QoS API can be used to control this CPU's idle state
> selection and limit just enter the shallowest idle state to low the delay
> after sleep by setting strict resume latency (zero value).
> 
> [1] https://www.kernel.org/doc/html/latest/admin-guide/abi-testing.html?highlight=pm_qos_resume_latency_us#abi-sys-devices-power-pm-qos-resume-latency-us


This is not a direct critique of this patch.
The power library should have been designed to take a single configuration structure
specifying CPU frequencies, wake up latency, and all the parameters from the kernel.
And there would be a simple API with: rte_power_config_set() and rte_power_config_get().