Re: [RFC][PATCH] Reduce number of pointer derefs in various files (kernel/exit.c used as example)

[Matt Mackall <mpm@selenic.com>]

On Tue, Dec 06, 2005 at 11:15:28PM +0100, Ingo Molnar wrote:
> 
> * Jesper Juhl <jesper.juhl@gmail.com> wrote:
> 
> > Ohh, and before I forget, besides the fact that this should speed 
> > things up a little bit it also has the added benefit of reducing the 
> > size of the generated code. The original kernel/exit.o file was 19604 
> > bytes in size, the patched one is 19508 bytes in size.
> 
> nice. Just to underline your point, on x86, with gcc 4.0.2, i'm getting 
> this with your patch:
> 
>    text    data     bss     dec     hex filename
>   11077       0       0   11077    2b45 exit.o.orig
>   10997       0       0   10997    2af5 exit.o
> 
> so 80 bytes shaved off. I think such patches also increase readability.

Readability improved: good.
37 lines of patch for 80-100 bytes saved: not so good.

So while this is a good style direction, I don't think it's worth the
churn. And unlike kzalloc and the like, this particular optimization
is perfectly doable by a compiler. So I'd rather wait for the compiler
to get smarter than change code for such modest improvements.

FYI, much other low-hanging size-reduction fruit remains in the
kernel. Lots of it in the form of duplicate code.

-- 
Mathematics is the supreme nostalgia of our time.