NAME

profil − execution time profile

SYNOPSIS

profil(buff, bufsiz, offset, scale)
char \(**buff;
int bufsiz, offset, scale;

DESCRIPTION

Buff points to an area of core whose length (in bytes) is given by bufsiz. After this call, the user’s program counter (pc) is examined each clock tick (60th second); offset is subtracted from it, and the result multiplied by scale. If the resulting number corresponds to a word inside buff, that word is incremented. 

The scale is interpreted as an unsigned, fixed-point fraction with binary point at the left: 0177777(8) gives a 1-1 mapping of pc’s to words in buff; 077777(8) maps each pair of instruction words together.  02(8) maps all instructions onto the beginning of buff (producing a non-interrupting core clock). 

Profiling is turned off by giving a scale of 0 or 1.  It is rendered ineffective by giving a bufsiz of 0.  Profiling is turned off when an exec is executed, but remains on in child and parent both after a fork. Profiling may be turned off if an update in buff would cause a memory fault.  Profiling will be turned off if an increment to a word in buff would cause that counter to overflow.  This preserves the scaling of the data. 

SEE ALSO

monitor(3), prof(1)

ASSEMBLER (PDP-11)

(profil = 44.) 
sys profil; buff; bufsiz; offset; scale

BUGS

Profiling does not work for interpreters; if a signal were given to a process when its cpu-time clock ticked then profiling interpreters would be possible. 

4th Berkeley Distribution  —  %W%%Q%%Y%