Linux Games/Apps Might Get Greater Control Over GPU Frequency On Intel Hardware
The 36 patches conclude with supporting per-context user requests for GPU frequency control. Basically it's for allowing games or applications -- like multimedia programs -- to opt-in to trying to select/request their GPU frequency rather than leaving it up to the driver. In performance-sensitive situations like games or video playback, this may be beneficial for delivering a more desirable experience if the application/engine has the logic for better determining how fast/slow of a GPU it can get by with for processing.
Chris Wilson explained the logic in the final patch:
Often, we find ourselves facing a workload where the user knows in advance what GPU frequency they require for it to complete in a timely manner, and using past experience they can outperform the HW assisted RPS autotuning. An example might be kodi (HTPC) where they know that video decoding and compositing require a minimum frequency to avoid ever dropping a frame, or conversely know when they are in a powersaving mode and would rather have slower updates than ramp up the GPU frequency and power consumption. Other workloads may defeat the autotuning entirely and need manual control to meet their performance goals, e.g. bursty applications which require low latency.
To accommodate the varying needs of different applications, that may be running concurrently, we want a more flexible system than a global limit supplied by sysfs. To this end, we offer the application the option to set their desired frequency bounds on the context itself, and apply those bounds when we execute commands from the application, switching between bounds just as easily as we switch between the clients themselves.
The patch series can be found here and perhaps we'll see the work materialize for the just-started Linux 4.18 DRM cycle.
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