Of the many new features in Linux 6.13 for that kernel debuting by late January, AMD customers once again have a lot to look forward to from new Zen 5 features being enabled to additional performance optimizations. Here is a look at some of the most exciting new AMD features and improvements with this first major Linux kernel release coming for 2025.
A new AMD driver debuting in the Linux 6.13 kernel is the AMD 3D V-Cache Optimizer driver. This driver for AMD Ryzen X3D 3D V-Cache processors allow users to communicate their cache vs. frequency preference for best handling of new tasks on the system. This optimizer driver is for AMD Zen CPUs with multiple CCDs but where only a subset of them have the larger L3 cache (3D V-Cache) and the other CCDs able to boost more easily to a higher performance state. Via a new “amd_x3d_mode” sysfs node exposed on Linux 6.13+, users can set whether they prefer new tasks be placed on the CCD with the higher frequency or whether to prioritize the CCD with the larger L3 cache.
Over on the EPYC side in Linux 6.13, the new kernel is now defaulting to the AMD P-State driver rather than ACPI CPUFreq. This change is just for the EPYC 9005 “Turin” and future processors. For a number of kernels now the AMD Ryzen CPUs (and in turn the EPYC 4004 series too) have been defaulting to the AMD P-State driver but now for the big EPYC server processors they kept to using the generic ACPI CPUFreq CPU frequency scaling driver. But for Linux 6.13+ the AMD EPYC 9005 series and beyond will be using AMD P-State now too for better power efficiency and performance. This does require the server motherboard to expose ACPI CPPC for AMD P-State support otherwise ACPI CPUFreq will still be used. There are nice power efficiency wins on 5th Gen EPYC with AMD P-State and I will have more benchmarks soon.
There are also some nice incremental performance improvements found during testing with 5th Gen EPYC “Turin” CPUs, even if the server/motherboard doesn’t support using AMD P-State (due to issues with or lacking ACPI CPPC) and thus still using ACPI CPUFreq.
Another useful Linux 6.13 addition for those on the new 5th Gen AMD EPYC servers is PCI Express TLP Processing Hints support. The PCIe TLP Processing Hints (TPH) are optional hints that can be injected for improving latency and lowering traffic congestion when there are several possible cache locations on the system. Paired with Smart Data Cache Injection on EPYC Zen 5 this can lead to better I/O performance.
A new AMD Zen 5 feature at large now supported by Linux 6.13 is the AMD Bus Lock Trap handling and similar to the Intel bus lock detection support that’s been around for a while. Linux 6.13 also adds new Zen 5 perf events.
There are also new AMD CPU features with Linux 6.13 such as a feature flag to denote AMD processors supporting workload classification for hints around kernel scheduler decisions. There is also a patch to determine the boost enumerator correctly for AMD cores whether they are the legacy or dense core versions. Plus other ongoing AMD heterogeneous CPU topology work for the Linux kernel.
For those still using older AMD processors, there is a fix for Zen 1 / Zen 2 CPU microcode updates leading to slow boot times.
Over on the AMD graphics side is support with the Radeon RX 7000 series graphics cards for being able to toggle the Zero RPM feature if not desired. There’s also continued work on RDNA4 graphics as well as new features like runtime re-partitioning for CDNA / Instinct accelerators.
Some other AMD changes in the Linux 6.13 kernel include AMD I3C controller ACPI support in the DesignWare driver, AMD ACP 6.3 SoundWire support with various codecs, and more.
Plus there are many other general improvements that benefit AMD customers and others like the ability to AutoFDO+Propeller optimized kernel builds with Clang, NVMe 2.1 device support, both Intel and AMD CPUs enjoying faster CRC32C and AEGIS-128 crypto, and other new hardware peripheral/adapter enablement.
Simply put, Linux 6.13 will be debuting as stable in January as a very nice post-holiday treat for AMD Linux users whether you are a laptop/desktop user or deploying large EPYC servers. And then after that is the Linux 6.14 kernel cycle for a spring debut and already a number of new AMD improvements coming there too.
