Re: [PATCH v2 2/4] QoS: Enhance framework to support per-cpu PM QoS request

[Kevin Hilman <khilman@linaro.org>]

Lina Iyer <lina.iyer@linaro.org> writes:

> QoS request can be better optimized if the request can be set only for
> the required cpus and not all cpus. This helps save power on other
> cores, while still gauranteeing the quality of service on the desired
> cores.
>
> Add a new enumeration to specify the PM QoS request type. The enums help
> specify what is the intended target cpu of the request.
>
> Enhance the QoS constraints data structures to support target value for
> each core. Requests specify if the QoS is applicable to all cores
> (default) or to a selective subset of the cores or to a core(s).
>
> Idle and interested drivers can request a PM QoS value for a constraint
> across all cpus, or a specific cpu or a set of cpus. Separate APIs have
> been added to request for individual cpu or a cpumask.  The default
> behaviour of PM QoS is maintained i.e, requests that do not specify a
> type of the request will continue to be effected on all cores.
>
> The userspace sysfs interface does not support setting cpumask of a PM
> QoS request.
>
> Signed-off-by: Praveen Chidambaram <pchidamb@codeaurora.org>
> Signed-off-by: Lina Iyer <lina.iyer@linaro.org>

I'm curious if you looked at using the per-device QoS API for this
instead of expending the system-wide API.  IOW, from a per-device QoS
POV, a CPU is no different than any other device, and since we already
have the per-device QoS API, I wondered if that might be a better choice
to implment this per-CPU feature.

Kevin