Five years ago Intel began introducing “workload hints” used for thermal and power purposes with their SoCs and in turn on the software-side being enabled with their INT340X kernel driver on Linux systems. That Intel workload hint coverage was added to the Linux kernel in late 2020 and then a big addition in 2023 with Meteor Lake introducing new workload hint type capabilities. Now patches have been posted to the Linux kernel mailing list for new workload hint functionality coming for upcoming Panther Lake SoCs.
The Linux kernel support for Panther Lake SoCs has been largely settled now with Linux ~6.18+ but a few late features have surfaced. The newest feature work happening for Intel Panther Lake within the Linux kernel is the notion of slow workload hints for their thermal driver.
This isn’t slow in the context of the SoC/CPU being slow but rather a slow-running process and thus to apply workload hint classification over the longer-term and ignoring shorter-term workload fluctuations. The new Intel INT340X driver patch explains of the new slow workload hints:
“On processors starting from Panther Lake additional hints are provided. The hardware analyzes workload residencies over an extended period to determine whether the workload classification tends toward idle/battery life states or sustained/performance states. Based on this long-term analysis, it classifies: Power Classification: If the workload exhibits more idle or battery life residencies, it is classified as “power”. This is indicated by setting the bit 4 of the current workload type. Performance Classification: If the workload exhibits more sustained or performance residencies, it is classified as “performance”. This is indicated by resetting the bit 4 of the current workload type.
This approach enables applications to ignore short-term workload fluctuations and instead respond to longer-term power vs. performance trends. This types of hints are called slow workload hints.
To get notifications for slow workload hints, a new bit 22 is added to thermal mailbox to configure workload interrupts. This is possible to exclusively only enable slow workload hints or enable in addition to the current workload hints.
To enable slow workload hint a new attribute is added to the existing workload hint attributes: workload_slow_hint_enable (RW): Write 1 to enable, 0 to disable. Reading this attribute shows the current state.
This attribute is not present any previous generation of processors.”
This patch series is now out for review on the mailing list. But with the Linux 6.19 merge window having passed, this feature code won’t be merged until Linux 6.20 (7.0) at the earliest and thus not being in a stable kernel until April. Hopefully before April we’ll already be seeing Intel Panther Lake laptops on Linux.
