Queued up into DRM-Next is a last batch of Intel Xe kernel graphics driver improvements ahead of the Linux 6.18 merge window that is expected to begin next week. With this last minute Intel Xe driver activity is also a new power management knob for those wanting to run their Intel graphics slightly more efficient.
The new addition in drm-xe-next worth mentioning is the SLPC “slpc_power_profile” sysfs interface. This allows manipulating the Single Loop Power Controller (SLPC) between its base (default) state and a “power_saving” mode.
We’ve seen Intel work on SLPC power management enhancements in the past and this latest addition for Linux 6.18 lets users adjust the state by reading/writing to the “slpc_power_profile” under the DRM sysfs entries.
The power saving mode for the SLPC will put the graphics processor into more conservative up/down thresholds and is intended for apps that typically desire being more power efficient. Digging through the patch, some code comments further explain this functionality:
“Single Loop Power Control (SLPC) is a GuC algorithm that manages GT frequency based on busyness and how KMD initializes it. SLPC is almost completely in control after initialization except for a few scenarios mentioned below.
KMD uses the concept of waitboost to ramp frequency to RP0 when there are pending submissions for a context. It achieves this by sending GuC a request to update the min frequency to RP0. Waitboost is disabled when the request retires.
Another form of frequency control happens through per-context hints. A context can be marked as low latency during creation. That will ensure that SLPC uses an aggressive frequency ramp when that context is active.
Power profiles add another level of control to these mechanisms. When power saving profile is chosen, SLPC will use conservative thresholds to ramp frequency, thus saving power. KMD will disable waitboosts as well, which achieves further power savings. Base profile is default and ensures balanced performance for any workload.”
No power numbers were provided as part of the patch to quantify the impact on power savings that the SLPC power profile mode will present. In any case you can expect to find “slpc_power_profile” as part of Linux 6.18 for use with recent Intel graphics hardware.
This SLPC power profile feature was merged to DRM-Next via this pull request ahead of the imminent Linux 6.18 merge window.
