AMD Ryzen 9 3900X SMT Linux Performance Benchmarks

For those wondering what the SMT performance impact is for new Zen 2 processors, here are some tests done using a Ryzen 9 3900X with Ubuntu Linux when testing at the default 12-core / 24-threads and then again when disabling SMT to look at just the twelve physical cores.

A few premium supporters wrote in recently wondering how the SMT performance looks on Linux for the new AMD CPUs and if it differs at all from Windows' SMT performance. Besides the recent Windows vs. Linux Ryzen 9 3900X benchmarks I haven't done a cross-OS SMT comparison yet, but here are some side-by-side tests looking at Ubuntu when toggling SMT from the BIOS.

Obviously toggling SMT was the only change made during this round of Linux benchmarking via the Phoronix Test Suite.

For a mix of different workloads from dozens of benchmarks, the geometric mean of all the results was boosted by just 4% with SMT.

When looking at some of the extremes, in many of the highly-threaded workloads there were significant gains to find out of the Ryzen 9 3900X with SMT. But in some of the multi-threaded tests when becoming over-subscribed the performance did suffer. Interestingly Intel's MKL-DNN math kernel library was one of the workloads suffering the most from SMT.

Those wanting to dig through all of the numbers can do so via this OpenBenchmarking.org result file.