profil(2) control process profiling


Lb libc


In unistd.h Ft int Fn profil char *samples size_t size vm_offset_t offset int scale


The Fn profil system call enables or disables program counter profiling of the current process. If profiling is enabled, then at every profiling clock tick, the kernel updates an appropriate count in the Fa samples buffer. The frequency of the profiling clock is recorded in the header in the profiling output file.

The buffer Fa samples contains Fa 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 profiling 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 Fa offset argument is the lowest address at which the kernel takes program counter samples. The Fa scale argument 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 Fa scale value of 0 disables profiling.


Rv -std profil


profiling C run-time startup file
conventional name for profiling output file


The following error may be reported:

The buffer Fa samples contains an invalid address.


The Fn profil function appeared in AT&T System v7 .


This routine should be named Fn profile .

The Fa samples argument should really be a vector of type Fa unsigned short .

The format of the gmon.out file is undocumented.