Subject: Re: Bad count of CPUs -- On Hyper Threading
To: Joseph A. Dacuma <email@example.com>
From: Manuel Bouyer <firstname.lastname@example.org>
Date: 10/14/2006 22:40:40
On Thu, Oct 12, 2006 at 08:56:54PM +0800, Joseph A. Dacuma wrote:
> > On Thu, Oct 12, 2006 at 04:01:40AM +0800, Joseph A. Dacuma wrote:
> >> Is it wise to enable HT? I came across various sites where they say
> >> Hyper
> >> Threading makes a system unstable.
> > s/unstable/slow/
> > Unless your scheduler completely understands HT, and assigns processes
> > accordingly, and unless all the idle loops and busy-wait loops are
> > HT correct, you could easily be better off disabling HT.
> > To some extent HT is a win under windows because its scheduler is so bad
> > at handling spinning processes.
> > David
> Dear Sirs,
> Thank you very much for all the info on HT. My last question is, does
> NetBSD completely understand HT? Or will one be better off disabling it
> completely since the performance gains is not that glaring compared to the
> risks involved when enabled for common systems.
There's should be no risk, but as NetBSD's scheduler isn't HT-aware
for some applications it can be slower. You have to test to be sure, though
Manuel Bouyer <email@example.com>
NetBSD: 26 ans d'experience feront toujours la difference