The Performance Hit For A Xeon-Backed Ubuntu Linux VM With L1TF / Foreshadow Patches

The out-of-the-box/default mitigation for L1TF is quite small in pure CPU workloads like the TTSIOD renderer, but obviously the full mitigation that disables SMT/HT has a significant impact on these multi-threaded tests.

The time to compile large code-bases like LLVM was up by a few seconds due to the mitigation or more noticeably under l1tf=full.

The Hackbench Linux kernel scheduler benchmark is one of the cases that shows the impact of always flushing the L1D cache rather than the default conditional flushing.

Fortunately, Hackbench is a synthetic benchmark.

The OpenSSL signing performance was affected minimally on this 64-thread VM backed by dual Xeon CPUs.