On Thu, Jun 02, 2011 at 09:21:11PM +0100, David Laight wrote:
> 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.
Well, an amd64 GENERIC kernel grows by 1.5k, and I've given up trying to get
an i386 MONOLITHIC to compile - too much crap in compat.
David
--
David Laight: [email protected]
