GET_CYCLECOUNT - reference manual online

Get the CPU's fast counter register contents.

March 15, 2011
GET_CYCLECOUNT(9)                 BSD Kernel Developer's Manual                 GET_CYCLECOUNT(9)

NAME get_cyclecount — get the CPU's fast counter register contents
SYNOPSIS #include <sys/param.h> #include <sys/systm.h> #include <machine/cpu.h> uint64_t get_cyclecount(void);
DESCRIPTION The get_cyclecount() function uses a register available in most modern CPUs to return a value that is monotonically increasing inside each CPU. On SMP systems, there will be a number of separate monotonic sequences, one for each CPU running. The value in the SMP case is selected from one of these sequences, dependent on which CPU was scheduled to service the request. The speed and the maximum value of each counter is CPU-dependent. Some CPUs (such as the Intel 80486) do not have such a register, so get_cyclecount() on these platforms returns a (monotonic) combination of numbers represented by the structure returned by binuptime(9). The AMD64 and Intel 64 processors use the TSC register. The IA64 processors use the AR.ITC register.
SEE ALSO binuptime(9)
HISTORY The get_cyclecount() function first appeared in FreeBSD 5.0.
AUTHORS This manual page was written by Mark Murray <>.
BSD March 15, 2011 BSD
This manual Reference Other manuals
get_cyclecount(9freebsd) referred by
refer to binuptime(9freebsd)