From owner-freebsd-hackers@FreeBSD.ORG Tue Mar 10 02:57:38 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 38F7623E for ; Tue, 10 Mar 2015 02:57:38 +0000 (UTC) Received: from na01-bn1-obe.outbound.protection.outlook.com (mail-bn1bon0083.outbound.protection.outlook.com [157.56.111.83]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (Client CN "mail.protection.outlook.com", Issuer "MSIT Machine Auth CA 2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id CD935DAA for ; Tue, 10 Mar 2015 02:57:36 +0000 (UTC) Received: from DM2PR0801MB0944.namprd08.prod.outlook.com (25.160.131.27) by DM2PR0801MB0942.namprd08.prod.outlook.com (25.160.131.25) with Microsoft SMTP Server (TLS) id 15.1.106.15; Tue, 10 Mar 2015 01:24:35 +0000 Received: from DM2PR0801MB0944.namprd08.prod.outlook.com ([25.160.131.27]) by DM2PR0801MB0944.namprd08.prod.outlook.com ([25.160.131.27]) with mapi id 15.01.0106.007; Tue, 10 Mar 2015 01:24:35 +0000 From: "Pokala, Ravi" To: Rui Paulo Subject: Re: detecting hyperthreading Thread-Topic: detecting hyperthreading Thread-Index: AQHQWqyImRFHWPGSCkqtx00nVjUfFZ0U6yCA//+MIIA= Date: Tue, 10 Mar 2015 01:24:35 +0000 Message-ID: References: <9F2E1411-B517-4BC8-AF61-BB15EE35083C@me.com> In-Reply-To: <9F2E1411-B517-4BC8-AF61-BB15EE35083C@me.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: user-agent: Microsoft-MacOutlook/14.4.8.150116 x-originating-ip: [64.80.217.3] authentication-results: me.com; dkim=none (message not signed) header.d=none; x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:DM2PR0801MB0942; x-microsoft-antispam-prvs: x-forefront-antispam-report: BMV:1; SFV:NSPM; SFS:(10009020)(6009001)(377424004)(51444003)(13464003)(2656002)(106116001)(36756003)(92566002)(46102003)(62966003)(76176999)(77156002)(99286002)(66066001)(102836002)(50986999)(86362001)(83506001)(19580395003)(2950100001)(122556002)(19580405001)(87936001)(221733001)(110136001)(54356999)(2900100001)(40100003)(7059030)(111123002); DIR:OUT; SFP:1101; SCL:1; SRVR:DM2PR0801MB0942; H:DM2PR0801MB0944.namprd08.prod.outlook.com; FPR:; SPF:None; MLV:sfv; LANG:en; x-exchange-antispam-report-test: UriScan:; x-exchange-antispam-report-cfa-test: BCL:0; PCL:0; RULEID:(601004)(5005006)(5002009); SRVR:DM2PR0801MB0942; BCL:0; PCL:0; RULEID:; SRVR:DM2PR0801MB0942; x-forefront-prvs: 051158ECBB Content-Type: text/plain; charset="us-ascii" Content-ID: <0D69E1BB803CCE4EBA5CE1E39241C3DD@namprd08.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: panasas.com X-MS-Exchange-CrossTenant-originalarrivaltime: 10 Mar 2015 01:24:35.2127 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: acf01c9d-c699-42af-bdbb-44bf582e60b0 X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM2PR0801MB0942 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 02:57:38 -0000 -----Original Message----- From: Rui Paulo Date: 2015-03-09, Monday at 18:19 To: Ravi Pokala Cc: "freebsd-hackers@freebsd.org" Subject: Re: detecting hyperthreading >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. I never tried to *change* it at runtime; I just used it's *existence* as an indicator that HT was enabled. (Aside - why did it not exist at all when HT was disabled, as opposed to always existing and just having zero/non-zero values?) -Ravi >-- >Rui Paulo