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get_cyclecount(9) [debian man page]

GET_CYCLECOUNT(9)					   BSD Kernel Developer's Manual					 GET_CYCLECOUNT(9)

get_cyclecount -- get the CPU's fast counter register contents SYNOPSIS
#include <sys/param.h> #include <sys/systm.h> #include <machine/cpu.h> u_int64_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 the number of nanoseconds represented by the structure returned by nanotime(9). The Pentium processors all use the TSC register. The Alpha processors use the PCC register. The IA64 processors use the AR.ITC register. SEE ALSO
nanotime(9) HISTORY
The get_cyclecount() function first appeared in FreeBSD 5.0. AUTHORS
This manual page was written by Mark Murray <>. BSD
November 20, 2000 BSD

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I386_PMC_INFO(2)					   BSD/i386 System Calls Manual 					  I386_PMC_INFO(2)

i386_pmc_info, i386_pmc_startstop, i386_pmc_read -- interface to CPU performance counters LIBRARY
i386 Architecture Library (libi386, -li386) SYNOPSIS
#include <sys/types.h> #include <machine/sysarch.h> #include <machine/specialreg.h> int i386_pmc_info(struct i386_pmc_info_args *ia); int i386_pmc_startstop(struct i386_pmc_startstop_args *ssa); int i386_pmc_read(struct i386_pmc_read_args *ra); DESCRIPTION
These functions provide an interface to the CPU performance counters on the 586-class and 686-class processors. i386_pmc_info() will return information about the available CPU counters. The information is returned in ia having the following structure: struct i386_pmc_info_args { int type; int flags; }; The type member describes the class of performance counters available. Valid values are: PMC_TYPE_NONE No PMC support PMC_TYPE_I586 586-class CPUs PMC_TYPE_I686 686-class Intel CPUs PMC_TYPE_K7 686-class AMD CPUs The flags member describes additional capabilities of the processor. Valid values are: PMC_INFO_HASTSC CPU has time-stamp counter i386_pmc_startstop() is used to start and stop the measurement of the CPU performance counters. The argument ssa has the following struc- ture: struct i386_pmc_startstop_args { int counter; uint64_t val; uint8_t event; uint8_t unit; uint8_t compare; uint8_t flags; }; The counter specified by the member counter is started if the member flags has PMC_SETUP_KERNEL or PMC_SETUP_USER set, otherwise the counter is stopped. The initial value of the counter is set to val. Additional values for the flags member are PMC_SETUP_EDGE and PMC_SETUP_INV. The event member specifies some event written to the control register. The unit member specifies the measurement units. The compare member is a mask for the counter. i386_pmc_read() will return information about a specific CPU counter measured during the last measurement period determined by the calling of i386_pmc_startstop(). The information is returned in ra having the following structure: struct i386_pmc_read_args { int counter; uint64_t val; uint64_t time; }; The counter to read should be specified by the counter member. Counters are numbered from 0 to PMC_NCOUNTERS. The value of the counter is returned in the val member. The time since epoch, measured in CPU clock cycles, is returned in the time member. RETURN VALUES
Upon successful completion zero is returned, otherwise -1 is returned on failure. BSD
November 10, 2001 BSD

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