In the i386 architecture, the timestamp counter is a monotonically
non-decreasing counter that counts processor cycles.
This counter may be selected specifying an event specifier
"tsc"
to
pmc_allocate(3).
The TSC is a read-only counter that may only be allocated in
system-wide counting mode.
The
"tsc"
event does not support further event qualifiers.
Multiple processes are allowed to allocate the TSC.
Once allocated, the TSC may be read using the
pmc_read()
function, or by using the
RDTSC
instruction.