Re: CVS commit: src/sys/kern

[David Laight <david%l8s.co.uk@localhost>]

On Thu, Jun 02, 2011 at 06:54:44PM +0000, David Laight wrote:
> Module Name:  src
> Committed By: dsl
> Date:         Thu Jun  2 18:54:44 UTC 2011
> 
> Modified Files:
>       src/sys/kern: vfs_syscalls.c
> 
> Log Message:
> Fix type in comment
> (before I replace the 'l' with 'curlwp')

Actually I've thought about this some more.
While, on the face of it, removing the 'struct lwp *' parameter to all system
calls might seem an optimisation, I suspect that, especially on systems where
arguments are passed in registers, it is a pessimisation.

Passing 'l' is a register rename (or copy) so is almost zero cost.

Recovering curlwp may involve a function call, and is, at best, a real
memory access of global data (possibly via an asm statement) that will
be slow and multiple accesses might need caching in a local anyway.

        David

-- 
David Laight: david%l8s.co.uk@localhost