Re: [PATCH] x86: eliminate redundant/contradicting cache line sizeconfig options

[Arjan van de Ven]

On Thu, 19 Nov 2009 04:56:40 +0100
Ingo Molnar <mingo@xxxxxxx> wrote:

> 
> * Nick Piggin <npiggin@xxxxxxx> wrote:
> 
> > The only other use for L1 cache size macro is to pack objects to 
> > cachelines better (so they always use the fewest number of lines).
> > But this case is more rare nowadays people don't really count
> > cachelines anymore, but I think even then it makes sense for it to
> > be the largest line size in the system because we don't know how
> > big L1s are, and if you want opimal L1 packing, you likely also
> > want optimal Ln packing.
> 
> We could do that - but then this default of X86_INTERNODE_CACHE_SHIFT:
> 
> +       default "7" if NUMA
> 
> will bite us and turns the 64 bytes L1_CACHE_BYTES into an effective
> 128 bytes value.
> 
> So ... are you arguing for an increase of the default x86 linesize to 
> 128 bytes?

128 is basically always wrong.
(unless you have a P4... but for default really we should not care
about those anymore)


-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/