PROFIL

Section: System Calls (2)
Index Return to Main Contents

BSD mandoc

NAME

profil - control process profiling

SYNOPSIS

Ft int Fn profil char *samples int size int offset int scale

DESCRIPTION

The Fn 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 Fa samples buffer.

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

RETURN VALUES

If the Fa scale value is nonzero and the buffer Fa samples contains an illegal address, Fn profil returns -1, profiling is terminated and errno is set appropriately. Otherwise Fn 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:

Bq Er EFAULT: The buffer Fa samples contains an invalid address.

BUGS

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.

This document was created by man2html, using the manual pages.
Time: 19:41:55 GMT, December 25, 2022