kprof(3) [plan9 man page]

KPROF(3)						     Library Functions Manual							  KPROF(3)

NAME

       kprof - kernel profiling

SYNOPSIS

       bind -a #T /dev

       /dev/kpctl
       /dev/kpdata

DESCRIPTION

       The kprof device provides simple profiling data for the operating system kernel.   The data accumulates by recording the program counter of
       the kernel at each `tick' of the system clock.

       The file kpdata holds the accumulated counts as 4-byte integers in big-endian byte order.  The size of the file depends on the size of ker-
       nel  text.   The first count holds the total number of clock ticks during profiling; the second the number of ticks that occurred while the
       kernel was running.  The rest each hold the number of ticks the kernel program counter was within the corresponding 8-byte range of  kernel
       text, starting from the base of kernel text.

       The  file kpctl controls profiling.  Writing the string start to kpctl begins profiling; stop terminates it.  The message startclr restarts
       profiling after zeroing the array of counts.

       The program kprof (see prof(1)) formats the data for presentation.

EXAMPLE

       The following rc(1) script runs a test program while profiling the kernel and reports the results.

	    bind -a '#T' /dev
	    echo start > /dev/kpctl
	    runtest
	    echo stop > /dev/kpctl
	    kprof /mips/9power /dev/kpdata

SOURCE

       /sys/src/9/port/devkprof.c

SEE ALSO

       prof(1)

																	  KPROF(3)

PROFIL(2)						      BSD System Calls Manual							 PROFIL(2)

NAME

     profil -- control process profiling

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

     int
     profil(char *samples, size_t size, vm_offset_t offset, int scale);

DESCRIPTION

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

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

RETURN VALUES

     The profil() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate
     the error.

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.

SEE ALSO

     gprof(1)

HISTORY

     The profil() function appeared in Version 7 AT&T UNIX.

BUGS

     This routine should be named profile().

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

     The format of the gmon.out file is undocumented.

BSD
								   June 4, 1993 							       BSD