LAT_SYSCALL(8)

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.