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)