Re: system call library functions

On Mon, Nov 29, 2004 at 01:06:05PM -0800, Dow Street wrote:
> All,
> 
> I am writing some benchmarking code for OS X 10.3.5.  When using 
> getpid() to measure the overhead of a system call, I find the overhead 
> to be much less than expected (1-3 clicks on the MPC 7447a TBR).  When 
> making the call using syscall(20), however, the measurement is as 
> expected (~33 clicks on the TBR).  Is getpid actually using a library 
> function which retrieves the PID from a user space data structure 
> (without entry into the kernel?)  Any idea what / where this function 
> is located and the data structure it's accessing?

getpid() caches the value, and updates it when needed (using fork(), etc).
All syscalls are wrappers in Libc.

Rob