Re: [patch] tlb flush_data: replace per_cpu with an array

Frederik Deweerdt
2009-01-14T14:49:30Z

On Wed, Jan 14, 2009 at 10:08:11AM +0100, Andi Kleen wrote:
>
> > > It also would save some memory
> > > on most distros out there (Ubuntu x86_64 has NR_CPUS=64 by default).
>
> As pointed out several times this claim in the changelog is incorrect.
> Please fix it.
>
> A correct description would be:
>
> - This patch wastes memory of one configured cache line for each CPU
> on systems with less than 8 cores (e.g. 896 bytes on a 1 core system
> with CONFIG_GENERIC_CPU/ cache line size 128)
> It saves some memory on systems with more than 8 cores (one cache
> line size for each core above 8)
To be fair, it also depends on whenever HOTPLUG_CPU is on or not (if it
is we allocate NR_CPUS percpu sections). In that case, which is Ubuntu's
and Fedora's, we do save memory.
This would make for a fairly long changelog, how about a link to this
thread, and removing the NR_CPUS bit?

Regards,
Frederik
>
> -Andi
>