Thanks Ralph. This is the same issue for me, in the syslog
TSC synchronization [CPU#0 -> CPU#1]:
Measured 2979160 cycles TSC warp between CPUs, turning off TSC clock.
tsc: Marking TSC unstable due to check_tsc_sync_source failed
and current_clocksource gives hpet. The other machines with good performance are all using TSC.
I haven’t been able to see how to fix this, and I wonder how common the issue is.