Re: [rfc][patch 1/3] slub: fix small HWCACHE_ALIGN alignment

Nick Piggin
2008-03-07T02:26:08Z

On Thu, Mar 06, 2008 at 06:20:40PM -0800, Christoph Lameter wrote:
> On Fri, 7 Mar 2008, Nick Piggin wrote:
>
> > > Do you have a case in mind where that would be useful? We had a
> >
> > Patch 3/3
>
> Those already have SLAB_HWCACHE_ALIGN.
>
> The point is to switch off alignment for UP? Cant we do that with
> SLAB_HWCACHE_ALIGN too since SLOB seemed to work successfully without it
> in the past?

See my next post to correct your understanding of HWCACHE_ALIGN.

> > > Note that there is also KMEM_CACHE which picks up the alignment from
> > > the compiler.
> >
> > Yeah, that's not quite as good either. My allocation flag is dynamic, so
> > it will not bloat things for no reason on UP machines and SMP kernels.
> > It also aligns to the detected machine cacheline size rather than a
> > compile time constant.
>
> Is that really a noteworthy effect?

Yes.