Re: [PATCH] Move some variables into the "most_readonly" section??

[Andi Kleen]

On Tue, Jun 14, 2005 at 04:27:55PM -0700, Christoph Lameter wrote:
> On Wed, 15 Jun 2005, Andi Kleen wrote:
> 
> > > If these maps would start in the middle of a cacheline then additional 
> > > cacheline fetches may become necessary to scan an array etc.
> > 
> > But the CPUs do prefetching anyways for that. Do you have numbers
> > that this is actually worth it? 
> 
> Its not only for scanning an array. A struct may contains a lot of 
> related information like for example boot_cpu_data. Aligning 
> increases locality and the likelyhood that no additional cachelines have 
> to be fetched.

On the other hand it will increase the overall working set so there might
be more cache misses again. It's a trade off and the outcome is not clear.

Do you have numbers? 

When in doubt I would suggest the less wasteful in memory solution.

-Andi
-
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/