From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from jaguar.aricent.com (jaguar.aricent.com [121.241.96.11]) by dpdk.org (Postfix) with ESMTP id 88AE23B5 for ; Tue, 7 Oct 2014 07:58:19 +0200 (CEST) Received: from jaguar.aricent.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 6FD122189D4; Tue, 7 Oct 2014 11:35:29 +0530 (IST) Received: from GUREXHT02.ASIAN.AD.ARICENT.COM (unknown [10.203.171.138]) by jaguar.aricent.com (Postfix) with ESMTPS id 5684B2189D1; Tue, 7 Oct 2014 11:35:29 +0530 (IST) Received: from GUREXMB01.asian.ad.aricent.com ([10.203.171.132]) by GUREXHT02.ASIAN.AD.ARICENT.COM ([10.203.171.138]) with mapi; Tue, 7 Oct 2014 11:35:28 +0530 From: Ravi Kumar Iyer To: "Ramia, Kannan Babu" , "dev@dpdk.org" Date: Tue, 7 Oct 2014 11:35:26 +0530 Thread-Topic: Queries related to Hyperthreading Thread-Index: AQHP4d7bTwtgqh2uckSVy5a9owetGZwkBT0ggAAeP/A= Message-ID: <5E927AAF66A09F419D11E0CDC6794A367EF926A2EF@GUREXMB01.ASIAN.AD.ARICENT.COM> References: <5E927AAF66A09F419D11E0CDC6794A367EF8AD85AB@GUREXMB01.ASIAN.AD.ARICENT.COM> <682698A055A0F44AA47192B20141149711B3E893@BGSMSX102.gar.corp.intel.com> In-Reply-To: <682698A055A0F44AA47192B20141149711B3E893@BGSMSX102.gar.corp.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-TM-AS-MML: disable Subject: Re: [dpdk-dev] Queries related to Hyperthreading X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 07 Oct 2014 05:58:20 -0000 Thanks Kannan, Do we have any links/docs where in we could read more about the behavior of= Hyperthreads. We are executing a code which is similar to the following example: So let us we have very tight loop of code which does basic arithmetic opera= tions[addition, subtraction]. Now the cost to complete these operations is = say C clock cycles on a single core[ with HT on]. Now if we run the same co= de with HT off, shouldn't the instruction pipeline of this code get execute= d faster [ theoretical at double speed]. Thanks ravi -----Original Message----- From: Ramia, Kannan Babu [mailto:kannan.babu.ramia@intel.com] Sent: Tuesday, October 07, 2014 9:48 AM To: Ravi Kumar Iyer; dev@dpdk.org Subject: RE: Queries related to Hyperthreading Hi Ravi The Intel HT actually has its own resources except few places like executio= n units and other resources in the pipeline, hence there are many factors p= lay here for the performance of the application with and without HT feature= . In simple words, even when you turned on the HT, and use only one of the = HT, then the performance will be more or less be similar to the core with H= T turned off. Also assume that if you are running same piece of code in bot= h the HTs, but it doesn't have lots have contention on the common resource = (you can figure out this using vTune profiling), then there will be very ma= rginal performance difference between HT turned ON Vs OFF. Regards Kannan Babu -----Original Message----- From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Ravi Kumar Iyer Sent: Tuesday, October 7, 2014 8:59 AM To: dev@dpdk.org Subject: [dpdk-dev] Queries related to Hyperthreading hello Intel Gurus, I have some queries related to intel HT technology. I am running an intel d= pdk application and trying to benchmark as well as optimize the same. As o= f now it is a single threaded application and would like to keep it like th= at for now. I am running it on an intel sandy bridge arch processor with HT= on. Now to increase the performance I have disabled HT, but am still getti= ng the same performance[ just a marginal improvement]. Now as per our under= standing so far wrt HT, two Hardware threads share the same physical core. = Now if we switch off HT[from bios] shouldn't just one hardware Thread get h= old of the complete CPU core. The application is heavily compute oriented = and as such minimal memory access or any IO operations. Appreciate any insi= ght on this. thanks ravi "DISCLAIMER: This message is proprietary to Aricent and is intended solely = for the use of the individual to whom it is addressed. It may contain privi= leged or confidential information and should not be circulated or used for = any purpose other than for what it is intended. If you have received this m= essage in error, please notify the originator immediately. 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