Re: [Xen-users] CPU's L2 cache size important?

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> I tried to find information on this myself, but unfortunately I didn't
> get very far.
> How important is the size of the CPU's L2 cache in regard to the
> performance of guest OS's under Xen?

That's a good question!

Obviously, having a better L2 cache size always ought to make things go 
faster.  In addition, for the same workload under Xen as native Linux, the 
Xen system has more code (apps + linux + xen) so it ought to have a larger 
cache footprint.  As a result, I guess I'd expect the extra cache to benefit 
Xen.  But I couldn't say how much, or to what extent it will affect your 
particular workload.

The best way would be to test both, I guess, but I suppose you probably can't 
do this.  I expect you'll find Xen runs OK on either system in terms of 
performance.  And since it's a laptop, I'm guessing that top performance 
isn't so critical as if you were running a server or something.

Your main problem is likely to be that Xen doesn't support laptop hardware / 
CPU frequency scaling / other power management as well as native Linux.

Cheers,
mark

> The reason I'm asking is that I have to choose between two notebooks,
> one with a smaller size and prize, but only 2MB L2 cache, and the
> other one with 4MB L2 cache.
> Does the size of the L2 cache has any significant impact on Xen
> performance?
>
> Many thanks for all opinions!
>
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-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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