Re: problems in linux-next (Was: Re: linux-next: Tree for December 1)
From: Ingo Molnar
Date: Tue Dec 01 2009 - 11:01:54 EST
* Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, 1 Dec 2009, Tejun Heo wrote:
>
> > The problem is that on UP configurations. Percpu memory allocator
> > becomes a simple wrapper around kmalloc and there's no way to
> > specify larger alignment when requesting memory from kmalloc.
>
> There is usually no point in aligning in UP. Alignment is typically
> done for smp configurations to limit cache line bouncing and control
> cache line use/
There is a natural minimum alignment for UP and it's smaller than the
cache-line size: machine word size. All our allocators (except bootmem)
align to machine word so there's no need to specify this explicitly.
Larger alignment than that just wastes memory - which waste UP systems
can afford the least.
Ingo
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