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Date:      Sat, 10 Nov 2007 01:26:15 -0800
From:      Maxim Sobolev <sobomax@FreeBSD.org>
To:        Bruce Evans <brde@optusnet.com.au>
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
Message-ID:  <47357937.6080400@FreeBSD.org>
In-Reply-To: <20071110190555.I35816@delplex.bde.org>
References:  <200711081945.lA8JjKcW080540@repoman.freebsd.org> <47337724.9040108@FreeBSD.org> <47337940.6040909@root.org> <47340B74.9070004@freebsd.org> <4734B13C.6050008@root.org> <4735008D.7030600@FreeBSD.org> <20071110190555.I35816@delplex.bde.org>

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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



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