Re: [PATCH] 2.5.21 Nonlinear CPU support

From: Andrew Morton (akpm@zip.com.au)
Date: Tue Jun 11 2002 - 02:42:32 EST


Rusty Russell wrote:
>
> Linus, please apply. Tested on my dual x86 box.
>
> This patch removes smp_num_cpus, cpu_number_map and cpu_logical_map
> from generic code, and uses cpu_online(cpu) instead, in preparation
> for hotplug CPUS.

umm. This patch does introduce a non-zero amount of bloat:
 
> ...
> - ntfs_compression_buffers = (u8**)kmalloc(smp_num_cpus * sizeof(u8*),
> + ntfs_compression_buffers = (u8**)kmalloc(NR_CPUS * sizeof(u8*),

and slowdown:

> ...
> --- linux-2.5.21.24110/kernel/sched.c Mon Jun 10 16:03:56 2002
> +++ linux-2.5.21.24110.updated/kernel/sched.c Tue Jun 11 13:53:32 2002
> ...
> @@ -530,15 +530,16 @@
>
> busiest = NULL;
> max_load = 1;
> - for (i = 0; i < smp_num_cpus; i++) {
> - int logical = cpu_logical_map(i);
> + for (i = 0; i < NR_CPUS; i++) {
> + if (!cpu_online(i))
> + continue;
>

and for the majority of SMP machines it gives nothing back, yes?

Is there some way of optimising all that?

-
-
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