PROFIL(2) MachTen Programmer’s Manual PROFIL(2)

NAME
profil - control process profiling

SYNOPSIS
int
profil(char *samples, int size, int offset, int scale)

DESCRIPTION
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 pro-
gram 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.

RETURN VALUES
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.

FILES
/usr/lib/gcrt0.o profiling C run-time startup file
gmon.out conventional name for profiling output file

ERRORS
The following error may be reported:

[EFAULT] The buffer samples contains an invalid address.