CVSROOT: /cvs
Module name: src
Changes by: kette...@cvs.openbsd.org 2020/07/03 11:54:27
Modified files:
sys/arch/amd64/amd64: tsc.c
sys/arch/amd64/include: cpufunc.h
Log message:
Use an LFENCE instruction everywhere where we use RDTSC when we are
doing some sort of time measurement. This is necessary since RDTSC
is not a serializing instruction. We can use LFENCE as the serializing
instruction instead of CPUID since all amd64 machines have SSE.
This considerably reduces the jitter in TSC skew measurements.
ok deraadt@, cheloha@, phessler@
