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Date: Sat, 10 Nov 2007 01:26:15 -0800
From: Maxim Sobolev <sobomax@FreeBSD.org>
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To: Bruce Evans <brde@optusnet.com.au>
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Cc: src-committers@FreeBSD.org, cvs-src@FreeBSD.org,
	Kris Kennaway <kris@FreeBSD.org>, cvs-all@FreeBSD.org,
	Colin Percival <cperciva@FreeBSD.org>, Nate Lawson <nate@root.org>
Subject: Re: cvs commit: src/sys/amd64/amd64 mp_machdep.c src/sys/i386/i386
 mp_machdep.c
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Bruce Evans wrote:
> Off is a good default since hyperthreading seems to be a pessimization
> in most casts.

Well, actually it all depends on workload and scheduling. I believe ULE 
is expected to improve things quite a bit in scheduling department. 
However, even with ol'good SCHED_BSD we measured noticeable performance 
increase (15-25%) in CPU intensive real-world tasks  with HTT enabled on 
2-way SMP Xeon system. It was in 2004, both CPUs and schedules should 
have been improved since that time.

-Maxim