NAME

       lat_syscall - time simple entry into the operating system

SYNOPSIS

       lat_syscall  [ -P <parallelism> ] [ -W <warmups> ] [ -N <repetitions> ] null|read|write|stat|fstat|open [
       file ]

DESCRIPTION

       null   measures how long it takes to do getppid().  We chose getppid() because in all  UNIX  variants  we
              are  aware  of,  it requires a round-trip to/from kernel space and the actual work required inside
              the kernel is small and bounded.

       read   measures how long it takes to read one byte from /dev/zero.  Note that some operating  systems  do
              not support /dev/zero.

       write  times  how  long it takes to write one byte to /dev/null.  This is useful as a lower bound cost on
              anything that has to interact with the operating system.

       stat   measures how long it takes to stat() a file whose inode is already cached.

       fstat  measures how long it takes to fstat() an open file whose inode is already cached.

       open   measures how long it takes to open() and then close() a file.

OUTPUT

       Output format is

       Null syscall: 67 microseconds

ACKNOWLEDGEMENT

       Funding for the development of this tool was provided by Sun Microsystems Computer Corporation.

SEE ALSO

       lmbench(8).

AUTHOR

       Carl Staelin and Larry McVoy

       Comments, suggestions, and bug reports are always welcome.

(c)1994 Larry McVoy                                  $Date$                                       LAT_SYSCALL(8)