Intel Alder Lake Users On Ubuntu 22.04 LTS Will Want To Switch To A Newer Kernel

Next week's Ubuntu 22.04 LTS "Jammy Jellyfish" is using Linux 5.15 by default given that the kernel is also a "Long Term Support" release. While it makes sense in theory, in practice with Linux 5.16 having been out as stable since January and Linux 5.17 out for several weeks already there is a lot of hardware improvements past the v5.15 that haven't been back-ported or otherwise picked up by Ubuntu Jammy's kernel build. The main pain point this presents is for those using the latest-generation Intel "Alder Lake" processors with a mix of performance and power efficiency cores. My testing of Alder Lake this week on the latest Ubuntu 22.04 LTS build still shows that its 5.15-based experience being less than desirable with measurable -- often very significant -- improvements if using v5.16 or later.

While the Intel Alder Lake S processors started shipping last November and usually Intel is well known for their very punctual Linux support over the past two decades, with the new hybrid architecture there were some challenges in making sure the Linux kernel makes the right decisions around P-core vs. E-core selection for tasks and that everything is all working nicely. One of the late patches was this November patch to Intel P-State for ensuring ITMT support for "overclocked" systems (overclocked in this case can simply be using an optimized BIOS configuration with optimal memory profile, etc). Since Linux 5.16, Alder Lake has been working out well across my tests on multiple systems with various processor SKUs.

So while Ubuntu 22.04 LTS is making use of Linux 5.15 LTS and coming out so many months after the Alder Lake introduction and while Linux 5.18 is the latest upstream version in development, I assumed they would be a bit more backport-heavy this time with their kernel build... Thus I was surprised in my testing of Ubuntu 22.04 LTS one week out from release that it wasn't so. Surprisingly, Ubuntu 22.04 LTS with Intel Alder Lake hybrid CPUs isn't in a good state. Users of Intel P/E-core hybrid CPUs will find a much better experience moving to at least Linux 5.16 if not Linux 5.17 stable. In this article are some benchmarks looking at the Intel Core i9 12900K on Ubuntu 21.10 compared to Ubuntu 22.04 as of this week in its effectively frozen state and then Ubuntu 22.04 when upgraded to Linux 5.16 / 5.17 / 5.18 Git kernels.

All of this Ubuntu testing of Intel Alder Lake was carried out on the same system with the Intel Core i9 12900K at stock speeds (in the automated system table, the 6.50GHz report is from a kernel bug where initially Alder Lake CPU clock speeds on Linux were reported much higher than they actually were - the same stock speeds and BIOS configuration were maintained across all benchmarks) with Alder Lake S GT1 graphics, ASUS ROG STRIX Z690-E GAMING WiFi motherboard, 2 x 16GB DDR5-5400 memory, and 2TB WD_BLACK SN850 NVMe solid-state drive. The system hardware and configuration were maintained the same for each benchmark run with just carrying out a clean Ubuntu install (or kernel upgrade) and proceeding to run the tests. The kernel upgrades were obtained from the Ubuntu Mainline Kernel PPA for easy reproducibility and for those wanting to quickly and easily fetch a newer Linux kernel build.