From owner-freebsd-current@FreeBSD.ORG  Thu Apr 12 22:39:16 2007
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: freebsd-current@FreeBSD.org
Delivered-To: freebsd-current@FreeBSD.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id C6C7616A401;
	Thu, 12 Apr 2007 22:39:16 +0000 (UTC)
	(envelope-from sobomax@FreeBSD.org)
Received: from sippysoft.com (gk.360sip.com [72.236.70.226])
	by mx1.freebsd.org (Postfix) with ESMTP id 8D67E13C448;
	Thu, 12 Apr 2007 22:39:16 +0000 (UTC)
	(envelope-from sobomax@FreeBSD.org)
Received: from [192.168.1.47] ([204.244.149.125]) (authenticated bits=0)
	by sippysoft.com (8.13.8/8.13.8) with ESMTP id l3CMPB4o098744
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO);
	Thu, 12 Apr 2007 15:25:13 -0700 (PDT)
	(envelope-from sobomax@FreeBSD.org)
Message-ID: <461EB188.3070303@FreeBSD.org>
Date: Thu, 12 Apr 2007 15:24:08 -0700
From: Maxim Sobolev <sobomax@FreeBSD.org>
Organization: Sippy Software, Inc.
User-Agent: Thunderbird 1.5.0.10 (Windows/20070221)
MIME-Version: 1.0
To: Julian Elischer <julian@elischer.org>
References: <461E0078.3050001@cisco.com>	<evl00c$89j$1@sea.gmane.org>	<461E092B.4080001@cisco.com>	<86d529zxci.fsf@dwp.des.no>	<20070412153930.A99718@fledge.watson.org>
	<461E74DA.3020402@elischer.org>
In-Reply-To: <461E74DA.3020402@elischer.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 8bit
Cc: Ivan Voras <ivoras@fer.hr>, Randall Stewart <rrs@cisco.com>,
	freebsd-current@FreeBSD.org, Robert Watson <rwatson@FreeBSD.org>,
	Janardhan Iyengar <iyengar@conncoll.edu>,
	=?ISO-8859-1?Q?Dag-Erling_Sm=F8rgrav?= <des@des.no>,
	Brad Penoff <penoff@cs.ubc.ca>
Subject: Re: CPU utilization
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 12 Apr 2007 22:39:16 -0000

Julian Elischer wrote:
> Robert Watson wrote:
>>
>> On Thu, 12 Apr 2007, Dag-Erling Smørgrav wrote:
>>
>>> Randall Stewart <rrs@cisco.com> writes:
>>>> machdep.hyperthreading_allowed: 0
>>>
>>> Note that enabling hyperthreading is more likely to harm performance 
>>> than to help it.  You should just disable it in the BIOS, and run a 
>>> UP kernel.
>>
>> Historically this has been true, but some more recent results I've 
>> seen suggest that both hyperthreading hardware has improved, and the 
>> efficiency of our SMP implementation and scheduler has lead to it 
>> being more effective used. I would reevaluate this on more modern 
>> hardware and using a more recent kernel before assuming this remains 
>> true for your application.
> 
> In addition to this, to answer the original question, I remember a 
> commit so that if you disable a cpu (or HT cpu) it doesn't get counted
> in the CPU % so if you have 2 cpus and disable one hten prior to that
> commit it was not possible to get > 50% busy but after that commit
> you could get 100% "of the available CPUs". That fix is not (I believe)
> in 6.2.

That's correct. The fix went in after RELENG_6_2 has been branched.

-Maxim