profil(2)							System Calls Manual							 profil(2)

NAME

       profil - Starts and stops execution profiling

SYNOPSIS

       void  profil(	   unsigned  short  *short_buffer,	 unsigned int buffer_size,	void  *offset,	    unsigned int scale ); #include
       <sys/resource.h>

       void profil(
	       struct profil_args *args,
	       int buffer_size,
	       -1,
	       unsigned long flags);

PARAMETERS

       Points to an area of memory in the user address space. Its length (in bytes) is given by the buffer_size parameter.  Specifies  the  length
       (in  bytes) of the buffer.  When offset is -1, indicating that the extended profil format shown in the second synopsis above is in use, the
       buffer_size parameter indicates the number of profil_args structures in the args array.	Specifies the delta of program counter	start  and
       buffer;	for  example, an offset of 0 (zero) implies that text begins at 0.  When offset is -1, the profil call is interpreted as a call to
       profile multiple discontiguous address ranges, such as those in an executable and its shared libraries.	In this type of profil call, which
       has  the  format  shown	in the second synopsis above, the buffer_size parameter indicates the number of profil_args structures in the args
       array.  Specifies the mapping factor between the program counter and short_buffer.  When offset is -1, specifies  an  array  of	up  to	64
       struct  profil_args  structures,  each  describing  a single address range in which profiling is to occur.  Specifies flags that modify the
       behavior of a profil call that profiles multiple discontiguous address ranges.  This argument is reserved for future use and should be 0.

DESCRIPTION

       The profil() function controls execution profiling.

       The short_buffer parameter points to an area of memory whose length (in bytes) is given by the buffer_size parameter.  After this call, the
       process'  program  counter  is examined at regular intervals (for example, at 1024 Hz).	To determine the interval for your system, use the
       getsysinfo(2) system call with GSI_CLK_TCK as the operation parameter.

       The value of the offset parameter is subtracted from the program counter, and the result multiplied by the  scale  parameter.   The  corre-
       sponding location in the short_buffer parameter is incremented if the resulting number is less than the buffer_size parameter.

       The  scale  parameter  is interpreted as an unsigned, fixed point fraction with 16 bits of mantissa:  0x10000  means that the address range
       has the same number of bytes as the short_buffer (that is, two bytes of instruction map into each short_buffer element); 0x8000	maps  four
       bytes of instructions into each short_buffer element; and so on.  The special scale factor of 2 maps all instructions onto the beginning of
       the short_buffer (producing a non-interrupting clock).

       Profiling is turned off by giving a scale parameter of either zero (0) or 1.  Profiling is turned off when an execve() is  executed.   Pro-
       filing  remains on in both the parent and child processes after a fork.	Profiling is turned off if an update in the short_buffer parameter
       would cause a memory fault.

       If the process contains multiple threads, each will be independently sampled and the counts will reflect the sum of the samples for all	of
       the threads.

       The  second  form  of  profil  call allows you to profile multiple disjoint address ranges, such as an executable and its shared libraries.
       This form of profil call must specify an offset of -1.  Its first argument, args, specifies an array of struct profil_args structures, each
       describing  a single address range in which profiling is to occur.  The buffer_size argument indicates the number of profil_args structures
       in the args array.

       The members of each profil_args structure in the array pointed to by args are similar to the arguments  in  the	traditional  profil  call,
       except  that the buffer field is an array of unsigned ints instead of an array of unsigned shorts, and the highpc and lowpc members specify
       both ends of the address range to be profiled.  The scale is still the ratio of bytes in the address range to bytes in the buffer.

       The following are the contents of a profil_args struct:
	       struct profil_args {
		       unsigned int    *buffer;
		       void	       *highpc;
		       void	       *lowpc
		       void	       *offset;
		       unsigned int    scale;
		       }

       All the address ranges specified in the array must be non-overlapping, and be ordered by decreasing lowpc value (that is, addresses  ranges
       appear  in  the	array  in  decreasing  beginning  address order).  As with a traditional profil call, profiling is turned off (for a given
       address range) if an update in the buffer (specified by the struct profil_args for that address range) would cause a memory fault.

       You can stop profiling started by either type of profil call by issuing the following command: profil(0,0,0,0)

       Because a traditional profil call stops all profiling started with an extended call, and an  extended  profil   call  stops  all  profiling
       started	with  a  traditional  call, a thread never needs to record both kinds of profiling activity at the same time. That is, profiling a
       single address range with a buffer of short  counters and profiling multiple address ranges in  buffers	with  int  counters  are  mutually
       exclusive  in  a given thread.  Although a thread can be switched from one type of profiling to the other with any call to the other inter-
       face and different profiling mechanisms can operate on separate threads simultaneously, use of a single profiling interface is  recommended
       in a single application.

RELATED INFORMATION

       Functions: exec(2), fork(2), getsysinfo(2), monitor(3)

       Commands: prof(1) delim off

																	 profil(2)