Subject: Re: Hyperthreading Guidance
To: John R. Shannon <>
From: Frank van der Linden <>
List: current-users
Date: 10/28/2003 20:38:55
On Tue, Oct 28, 2003 at 12:34:25PM -0700, John R. Shannon wrote:
> Am I better off enabling or disabling hyperthtreading on a twin Xeon system?
> The two "logical" CPUs are treated by the scheduler as ordinary processors?

They are, and that's why you're currently better off disabling HT.
Scheduling will be suboptimal. For example, if you have two runnable
processes, and one of them is running on a physical CPU, the other
one might be scheduled on the same physical CPU (using the 2nd virtual

The scheduler will require some reworking to avoid this.

- Frank

Frank van der Linden                                  
NetBSD. Free, Unix-like OS. > 45 different platforms.