How Do Spectre/Meltdown Mitigations Impact Ubuntu 20.04 Performance on Modern Intel CPUs?

To mark the two‑year anniversary of the public disclosure of Spectre and Meltdown, the author ran a fresh set of benchmarks on a range of Intel desktop and server processors using Ubuntu 20.04 LTS, first with the kernel’s default vulnerability mitigations enabled and then with those mitigations turned off.

The test environment uses Ubuntu 20.04 LTS built on the Linux 5.4 kernel, GCC 9.2.1 and the latest stable packages. By default the kernel applies mitigations for ITLB, L1TF, MDS, Meltdown, SSB (Spectre V2), Spectre V1, Spectre V2 and TSX Asynchronous Abort (TAA). To disable them the boot parameter mitigations=off is added; hyper‑threading and other CPU features remain enabled.

Desktop CPUs evaluated include:

Intel Core i7 5960X

Intel Core i7 8700K

Intel Core i5 9400F

Intel Core i9 9900K

Intel Core i9 10980XE (Cascadelake‑X)

Server CPUs evaluated include:

Intel Xeon E3‑1280 v5

Intel Xeon E3‑1275 v6

2 × Intel Xeon Platinum 8280

The Phoronix Test Suite was used with a variety of real‑world workloads to measure how the mitigations affect performance. On the newest Cascadelake‑X desktop processor, which incorporates many hardware‑based mitigations, the performance loss is considerably smaller than on older models, yet a residual overhead remains.

Overall, the benchmarks show that default Linux mitigations still impose a noticeable performance penalty on older Intel CPUs, while newer hardware mitigations significantly reduce—but do not entirely eliminate—the impact. Users can compare the two configurations to decide whether the security benefits outweigh the performance cost for their workloads.