An Early Look At The L1 Terminal Fault "L1TF" Performance Impact On Virtual Machines

Here is the basic SQLite embedded database library that's used by numerous applications on many different platforms. This test with its frequent syncs to the disk did see a performance hit from the default mitigation and slightly more so when always forcing the L1D cache flushing while the full mitigation with SMT disabled did cause more of a degradation but there was a higher variation in runs as well.

When running some purely CPU-focused benchmarks, there isn't any real performance impact as the cache flushing is infrequent but the full mitigation technique where SMT was disabled did obviously hurt the multi-threaded tests. Granted, it's important to keep in mind if your VMs have always been pinned to physical cores and not over-exposed with SMT, the performance impact should be much less notable...

In workloads like code compilation of large projects relying upon loading of files, the default mitigation or even with full L1D flushing there was a barely measurable impact on performance -- just a second or so for large code-bases like building the Linux kernel.