On Wed, Jan 19, 2005 at 10:59:08AM +0000, Peter O'Kane wrote:
> For what it's worth here are some kernel compile times on a dual Xeon 
> 2.4GHz system in different configurations. (NetBSD 2.0):
> 
> Single physical processor HT disabled:
> Real: 370.40s	User: 242.6s	System: 27.57s	(make)
> 
> Single physical processor HT enabled:
> Real: 306.13s	User: 374.68s	System: 41.34s	(make -j2)
> 
> Two physical processors HT disabled:
> Real: 236.42s	User: 248.66	System: 33.8s	(make -j2)
> 
> Two physical processors HT enabled:
> Real: 173.6s	User: 377.9s	System: 53.51s	(make -j4)
> Real: 151.54s	User: 435.04s	System: 69.11s	(make -j8)
> Real: 146.47s	User: 452.66s	System: 78.69s	(make -j16)
> 
> This system has all it's file systems on a 500G raid 5 array which makes it 
> quite i/o bound. There is 3G of RAM so there is no paging traffic.

It would have made more sense to use the same -j flag (e.g. -j8) for all your
tests. Even for a non HT single processor, -j8 will be faster than -j1,
because it will spend less time waiting on I/O.
Also, I suspect that the Xeon's HT isn't exactly the same as P4's HT.
The virtual processors may share more things in the P4 than in the xeon.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
     NetBSD: 26 ans d'experience feront toujours la difference
--