Linux Prepares For Intel Arrow Lake H With Mix Of Lion Cove, Skymont & Crestmont Cores

With upcoming Intel Arrow Lake H processors it's just not P cores and E cores but for the E cores will be a mix of both Skymont and Crestmont core types.

Intel Arrow Lake H series has been reported to consist of Lion Cove P cores and Skymont E cores. New Linux patches now indicate that it's not just Skymont cores for the E cores but also some Crestmont cores. Skymont is the newer Intel E-core type with reported double digit IPC gains over Crestmont found with Meteor Lake. But interesting for Arrow Lake H performance laptop processors the E cores aren't only Skymont but a mix with older Crestmont cores.

This morning a set of Linux PMU patches were posted for Arrow Lake H and indicate:

"ArrowLake-H is a specific variant of regular ArrowLake. It shares same PMU features on lioncove P-cores and skymont E-cores with regular ArrowLake except ArrowLake-H adds extra crestmont uarch E-cores.

Thus ArrowLake-H contains two different atom uarchs. This is totally different with previous Intel hybrid platforms which contains only one kind of atom uarchs. In this case, it's not enough to distinguish the uarchs just by core type. So CPUID.1AH.EAX[23:0] provides an unique native model ID for each uarch, this unique native model ID combining the core type can be used to uniquely identity the uarch.

This patch series introduces PMU support for ArrowLake-H. Besides inheriting the same PMU support from regular ArrowLake, it leverages the native model ID to detect the 2nd kind of atom uarch core and enables PMU support. To distinguish the two atom uarchs in sysfs, the PMU of 2nd atom uarch is named to "cpu_atom2"."

I don't pay much attention to rumors, but I believe to date Arrow Lake H has just been reported as using Lion Cove and Skymont. Previous indications have pointed to Arrow Lake H being configured up to 6 Lion Cove cores and 8 to 16 Skymont cores. Now with some older Crestmont cores joining the mix, it will be interesting to see the breakdown for the quantity of E cores for each type and Intel's justification for using both Crestmont and Skymont. It will also be interesting to see if this Arrow Lake H approach is a one-off pursuit by Intel or with future generations we'll also see a mix of heterogeneous E cores and/or P cores of different generations.

As for the ARL-H Linux PMU patches, the code is now under review and could be ready for merging with Linux v6.12 later this year. While Linux is still working to better handle Intel Core hybrid designs, let's hope the OS schedulers out there continue to evolve to cope well with the mix of three different core types of varying performance/power capabilities.