Date: Wed, 12 Jan 2005 21:53:39 +0100 From: Andrea Venturoli <ml@netfence.it> To: freebsd-questions@freebsd.org Subject: Re: Hyperthreading hurts 5.3? Message-ID: <41E58E53.7060606@netfence.it> In-Reply-To: <828997113.20050112184556@wanadoo.fr> References: <200501121049.j0CAnJQe028309@mp.cs.niu.edu> <828997113.20050112184556@wanadoo.fr>
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Anthony Atkielski wrote: >>From what you say and from what I've read today, it sounds like > hyperthreading comes close to providing two separate processors for > heterogenous system loads (where each hyperthread is using slightly > different processor resources at any given instant), but it may not buy > much of anything for massively parallel compute-bound work, FWIW I tried numerical computations on a P4 with HT enabled: I expected using 2 threads might give *at least slightly* better results, but I could come to the conclusion that with 1, 2 or 4 threads the performance gain (or loss) was exactly zero. (BTW, an old AMD 2000 XP+ would in any case almost outperform a P4 3GHz, but that's another story). Obviously your use (as a server) is very different, and probably the one test I have done can't expect to achieve 100% coverage even in this field... but, anyway, just my 2 cents... bye av.
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