Subject: Re: scheduler woes on MPACPI kernel
To: Peter O'Kane <email@example.com>
From: Manuel Bouyer <firstname.lastname@example.org>
Date: 01/19/2005 12:06:39
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 <email@example.com>
NetBSD: 26 ans d'experience feront toujours la difference