Looking At The Linux Performance Two Years After Spectre / Meltdown Mitigations
Databases like PostgreSQL, MySQL, and SQLite are some of the most common server workloads with measurable hits to the performance from these default mitigations. With Cascadelake is fortunately no measurable difference but for Skylake and Kabylake Xeons (and older) are clear differences.
Redis performance is another one showing real differences from Spectre/Meltdown on Ubuntu 20.04 LTS.
The context switching difference always is jaw dropping to look at from the CPUs relying entirely on software mitigations.