Re: [PATCH] sched.c

[Willy Tarreau <willy@w.ods.org>]

On Tue, Aug 27, 2002 at 09:15:03PM +0300, Lahti Oy wrote:
 
> - for (i = 0; i < NR_CPUS; i++)
> + for (i = NR_CPUS; i; i--)
>    sum += cpu_rq(i)->nr_running;

you change isn't equivalent : previously, we called cpu_rq() for
0..NR_CPUS-1, and now you call it for 1..NR_CPUS.

You should have written :
+ for (i = NR_CPUS - 1; i>=0; i--)
which might still be a win towards the former version.
But of course, this is only valid if i is SIGNED, and it isn't here.
Another valid form which would work with unsigned int is :
+ for (i = NR_CPUS; i--; )

but I'm not sure it will save some cycles because increments/decrements
within conditions are not always well optimizable.

Same comments for other locations.

Cheers,
Willy