Subject: Re: NetBSD SMP support (quad vs dual CPU)
To: Null Void <>
From: Ivan Voras <>
List: netbsd-users
Date: 11/11/2006 21:31:33
Null Void wrote:

> 1. DELL POWEREDGE 6650 QUAD Xeon 2Ghz with 4GB RAM for about $800
> 2. SuperMicro X5DPL-iGM Dual Xeon 2.4GHz 4GB RAM for about $700
> Considering NetBSD+Xen performance on dual vs quad CPU systems and factoring in the price, which one would you pick? From purely theoretical point of view, the quad CPU should perform better, but I know the devil is in the details and I've seen many cases where quad CPU systems perform worse than a dual ones with configuration similar to the one I've given above. Any advice/comments is appreciated.
> Thanks in advance.


I'm not a heavy NetBSD user so take this post with a grain of salt until
it's confirmed by someone who is :)

The choice would depend on two things:

1. Is NetBSD's kernel locking fine-grained or coarse? In other words,
does it have a giant lock that prevents multiple processes executing in
the kernel at the same time?
2. Does Xen execute mostly in the kernel or in userland?

If NetBSD is coarse-locked and Xen makes heavy use of the kernel,
speedier CPU will be better than more CPUs. In all other cases, more
CPUs is generally better.