Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [PATCH v2 RESEND] PM / devfreq: add PM QoS support | Date | Sun, 4 Mar 2012 23:30:33 +0100 |
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On Wednesday, February 29, 2012, Turquette, Mike wrote: > On Wed, Feb 29, 2012 at 1:43 AM, MyungJoo Ham <myungjoo.ham@samsung.com> wrote: > > + /* Check the sanity of qos_list/qos_type */ > > + if (profile->qos_type || profile->qos_list) { > > + switch (profile->qos_type) { > > + case PM_QOS_CPU_DMA_LATENCY: > > + case PM_QOS_NETWORK_LATENCY: > > + devfreq->qos_use_max = false; > > + break; > > + case PM_QOS_NETWORK_THROUGHPUT: > > + devfreq->qos_use_max = true; > > + break; > > Hello MyungJoo! > > I see that you re-using the same old PM QoS handles in this > implementation. Do you feel this is the right way to do it? Your > example of using DMA for multimedia devices (given in the changelog) > has nothing to do with network throughput, yet that constraint-type is > used here. > > I wonder if a better solution than overloading these classifications exist. > > Just to toss around ideas, what about having per-device PM QoS > throughput constraints which are generalized (e.g., not tied to a > concept such as "network"). I've Cc'd Jean Pihet (yet again) who has > some good experience making PM QoS-type interfaces work on a > per-device basis. > > I wonder, ultimately, if instead of feeding QoS constraints into > devfreq if a better design might be to have devfreq feed input into a > greater QoS framework. E.g: > > A scalable bus used by many devices might have two different device > drivers that want to call pm_qos_device_tput(...), and also the > devfreq driver for that bus also calls pm_qos_device_tput(...). So > essentially there are three points in the code where inputs can be > driven into one common per-device QoS layer for the generic concept of > "device throughput". This way devfreq support is not a prerequisite > for scaling a device in a generic way, but a nice framework for > devices which can monitor their own activity level, built on top of a > per-device pm qos layer. > > Thoughts?
I agree with the general idea, definitely would prefer it to what is currently being proposed.
Thanks, Rafael
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