How to determine the L2 cache size on non-AMD CPUs (automatic page queue color tuning)?

Alexander Leidinger Alexander at
Wed Jun 16 10:17:19 GMT 2004

On Wed, 16 Jun 2004 11:46:26 +0200
Martin Nilsson <martin at> wrote:

> Alexander Leidinger wrote:
> > Now I need to know how to determine those properties on at least some
> > Intel CPUs (e.g. P3 & P4).
> The more expensive intel processors also have L3 caches of 1-4MB.
> Since intels processors are built with inclusive caches (data in L2 
> cache is also present in L3) shouldn't the value used be that of the 
> largest cache be it L2 or L3?

Does the L3 cache have the same associativity as the L2 cache in those

> How much effct on performance does a wrong cache size value have?

I'm not very familiar with the cache coloring (I don't need to, to
change the tuning from a kernel option to autotuning), but AFAIK it
at least wouldn't hurt.

The actual way of choosing the number of colors is wrong, it allocates
more than the optimal number of colors. This isn't as bad as using less
than the optimal number of colors (or no colors at all). So we wouldn't
get bad performance compared to the actual way of tuning the coloring.
Actually we can get better performance, since a lot of people don't
know about the page coloring at all or how to tune it with the kernel

I think it's beneficial to tune to the L3 cache size (if present), but
let's give Alan the final words here...


           I'm available to get hired (preferred in .lu).                       Alexander @
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