man : profil(2)
PROFIL(2) OpenBSD Programmer's Manual PROFIL(2)
profil - control process profiling
profil(char *samples, size_t size, u_long offset, u_int scale);
The profil() function enables or disables program counter profiling of
the current process. If profiling is enabled, then at every clock tick,
the kernel updates an appropriate count in the samples buffer.
The buffer samples contains size bytes and is divided into a series of
16-bit bins. Each bin counts the number of times the program counter was
in a particular address range in the process when a clock tick occurred
while profiling was enabled. For a given program counter address, the
number of the corresponding bin is given by the relation:
[(pc - offset) / 2] * scale / 65536
The offset parameter is the lowest address at which the kernel takes
program counter samples. The scale parameter ranges from 1 to 65536 and
can be used to change the span of the bins. A scale of 65536 maps each
bin to 2 bytes of address range; a scale of 32768 gives 4 bytes, 16384
gives 8 bytes and so on. Intermediate values provide approximate
intermediate ranges. A scale value of 0 disables profiling.
If the scale value is nonzero and the buffer samples contains an illegal
address, profil() returns -1, profiling is terminated, and errno is set
appropriately. Otherwise, profil() returns 0.
/usr/lib/gcrt0.o profiling C run-time startup file
gmon.out conventional name for profiling output file
The following error may be reported:
[EFAULT] The buffer samples contains an invalid address.
This routine should be named profile().
The samples argument should really be a vector of type unsigned short.
The format of the gmon.out file is undocumented.
OpenBSD 4.9 May 31, 2007 OpenBSD 4.9