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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 sys-
       tem 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  kernel
       text.   The  first  count  holds the total number of clock ticks during
       profiling; the second the number of ticks that occurred while the  ker-
       nel  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 ker-
       nel 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)