AMD Ryzen 9 3900X SMT Linux Performance Benchmarks

Written by Michael Larabel in AMD on 1 August 2019 at 09:07 AM EDT. 14 Comments
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.
Ryzen 9 3900X Linux SMT Performance

Obviously toggling SMT was the only change made during this round of Linux benchmarking via the Phoronix Test Suite.
Ryzen 9 3900X Linux SMT Performance

For a mix of different workloads from dozens of benchmarks, the geometric mean of all the results was boosted by just 4% with SMT.
Ryzen 9 3900X Linux SMT Performance

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 result file.
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Michael Larabel

Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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