Merged for the Linux 6.13 kernel was the AMD 3D V-Cache Optimizer driver for being able to influence the kernel’s scheduling decisions on AMD processors where only a subset of CCDs have the larger 3D V-Cache. With this new driver users can communicate their cache vs. frequency preference for influencing where new tasks are first placed if on the CCD with the larger L3 cache or with the higher frequency potential. Here is a look at the impact of using the AMD 3D V-Cache Optimizer driver with the new AMD Ryzen 9 9950X3D.
AMD posted the 3D V-Cache Optimizer driver for Linux last October and now with the Ryzen 9 9950X3D launch is the first new product from AMD since the driver was mainlined back in Linux 6.13 to be able to it. Via the driver’s sysfs interface the cache vs. frequency preference can be set to affect the CPU core reordering depending upon whether you’re wanting new tasks to try to be placed on the higher frequency CCD or larger cache (3D V-Cache) CCD.
On Linux 6.13+ and when the kernel is built with the AMD_3D_VCACHE Kconfig option, on a Ryzen X3D processor like the Ryzen 9 9950X3D it’s possible to read the current preference via the /sys/bus/platform/drivers/amd_x3d_vcache/AMDI0101:00/amd_x3d_mode sysfs interface. By default for the Ryzen 9 9950X3D it was using the “frequency” preference as default. But if writing “cache” to /sys/bus/platform/drivers/amd_x3d_vcache/AMDI0101:00/amd_x3d_mode it will prefer using the CCD with the larger cache. This cache vs. frequency bias can all be easily manipulated at run-time for those interested.
For yesterday’s Ryzen 9 9950X3D Linux review all CPUs were benchmarked at their defaults on Linux 6.13. For this article is running through all of the Ryzen 9 9950X3D benchmarks again after setting the “cache” mode with the 3D V-Cache Optimizer driver. No other changes were made to the system during the testing besides opting for the cache preference.
Let’s see how this 3D V-Cache Optimizer driver bias change makes an impact on the brand new Ryzen 9 9950X3D under Linux. The benchmark results with the “- X3D Optimizer cache” are the new run using the 3D V-Cache Optimizer preference changed to cache.
