From owner-freebsd-hackers@FreeBSD.ORG Tue Mar 10 01:19:55 2015 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id A780E426 for ; Tue, 10 Mar 2015 01:19:55 +0000 (UTC) Received: from st11p02mm-asmtp002.mac.com (st11p02mm-asmtp002.mac.com [17.172.220.237]) (using TLSv1.2 with cipher DHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 7AC02FBF for ; Tue, 10 Mar 2015 01:19:55 +0000 (UTC) Received: from [10.17.4.36] (p31209-ipngn8001marunouchi.tokyo.ocn.ne.jp [153.214.94.209]) by st11p02mm-asmtp002.mac.com (Oracle Communications Messaging Server 7.0.5.35.0 64bit (built Dec 4 2014)) with ESMTPSA id <0NKZ00FAR2CAZQ50@st11p02mm-asmtp002.mac.com> for freebsd-hackers@freebsd.org; Tue, 10 Mar 2015 01:19:25 +0000 (GMT) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.13.68,1.0.33,0.0.0000 definitions=2015-03-09_05:2015-03-09,2015-03-09,1970-01-01 signatures=0 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=7.0.1-1412110000 definitions=main-1503100014 Content-type: text/plain; charset=us-ascii MIME-version: 1.0 (Mac OS X Mail 8.2 \(2070.6\)) Subject: Re: detecting hyperthreading From: Rui Paulo In-reply-to: Date: Tue, 10 Mar 2015 10:19:21 +0900 Content-transfer-encoding: quoted-printable Message-id: <9F2E1411-B517-4BC8-AF61-BB15EE35083C@me.com> References: To: "Pokala, Ravi" X-Mailer: Apple Mail (2.2070.6) Cc: "freebsd-hackers@freebsd.org" X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Mar 2015 01:19:55 -0000 On 10 Mar 2015, at 06:03, Pokala, Ravi wrote: >=20 > Hi folks, >=20 > There used to be a sysctl, "machdep.hyperthreading_allowed", which > indicated whether or not the kernel was using hyperthreaded cores. It > looks like it was removed sometime between 8 and 9, for perfectly good > reasons = (https://svnweb.freebsd.org/base?view=3Drevision&revision=3D222853). >=20 > That said, is there currently a way to tell at runtime from userland = if > hyperthreading is enabled or not? I think that sysctl didn't fully control hyperthreading: you can disable = it on the BIOS and FreeBSD never exported that information. If you used = that tunable, it would simply disable the Pentium 4 Hyperthreading. -- Rui Paulo