KPROF(3)                                                 KPROF(3)

     NAME
          kprof - kernel profiling

     SYNOPSIS
          bind -a #K /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 sys-
          tem 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 kernel 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 run-
          ning.  The rest each hold the number of total ticks the ker-
          nel spent at any one program counter, indexed by their
          offset from the minimum kernel text address.

          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 presen-
          tation.

     EXAMPLE
          The following rc(1) script runs a test program while profil-
          ing the kernel and reports the results.

               bind -a '#K' /dev
               echo start > /dev/kpctl
               runtest
               echo stop > /dev/kpctl
               kprof /386/9pcdisk /dev/kpdata

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

     SEE ALSO
          prof(1)