lat_syscall - time simple entry into the operating system
lat_syscall [ -P <parallelism> ] [ -W <warmups> ] [ -N <repetitions> ]
null|read|write|stat|fstat|open [ file ]
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
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 format is
Null syscall: 67 microseconds
Funding for the development of this tool was provided by Sun
Microsystems Computer Corporation.
Carl Staelin and Larry McVoy
Comments, suggestions, and bug reports are always welcome.
(c)1994 Larry McVoy $Date$