Last month AMD Linux engineers posted patches for a 3D V-Cache Optimizer driver for Linux that allows the user to communicate their cache vs. frequency preference depending upon workload and for the 3D V-Cache processors where some CCDs have the larger cache but not all. That driver is now ready for appearing in the upcoming Linux 6.13 kernel.
The Ryzen X3D processors with 3D V-Cache for some core complex dies (CCDs) but not all can now have a bias set under Linux whether it should be optimized for frequency mode or cache mode. When the 3D V-Cache optimizer driver is set to frequency mode, cores with the faster CCD are prioritized over the larger cache but lower clocked CCD.
Alternatively, the “cache mode” of the 3D V-Cache Optimizer Driver sets the preference to cores within the CCD where there is the larger L3 cache before the CCD with the smaller L3 cache.
The 3D V-Cache frequency vs. cache mode preference with this driver can be set by users via the /sys/bus/platform/drivers/amd_x3d_vcache/AMDI0101:00/amd_x3d_mode file. Writing a value to that sysfs file of “frequency” will set the frequency mode while “cache” will set the cache mode. Of course, reading from that file will tell you what mode the optimizer driver is currently functioning.
As of yesterday the AMD 3D V-Cache Optimizer Driver “amd_3d_vcache” was queued into platform-drivers-x86.git’s for-next branch. With it hitting that branch, it’s now set to be merged for the upcoming Linux 6.13 merge window. The Linux 6.13 merge window is expected to begin next week while the stable Linux 6.13 kernel won’t be out until around late January or early February. Some Linux distributions though like CachyOS have already decided to back-port this driver for their kernel builds.
