From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lists.gentoo.org ([140.105.134.102] helo=robin.gentoo.org) by nuthatch.gentoo.org with esmtp (Exim 4.43) id 1Dxf9V-0005Hd-EV for garchives@archives.gentoo.org; Wed, 27 Jul 2005 06:12:25 +0000 Received: from robin.gentoo.org (localhost [127.0.0.1]) by robin.gentoo.org (8.13.4/8.13.4) with SMTP id j6R6Apt3024870; Wed, 27 Jul 2005 06:10:51 GMT Received: from ciao.gmane.org (main.gmane.org [80.91.229.2]) by robin.gentoo.org (8.13.4/8.13.4) with ESMTP id j6R6Ap5V023186 for ; Wed, 27 Jul 2005 06:10:51 GMT Received: from list by ciao.gmane.org with local (Exim 4.43) id 1Dxf8E-00029f-EH for gentoo-amd64@lists.gentoo.org; Wed, 27 Jul 2005 08:11:06 +0200 Received: from ip68-230-97-182.ph.ph.cox.net ([68.230.97.182]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 27 Jul 2005 08:11:06 +0200 Received: from 1i5t5.duncan by ip68-230-97-182.ph.ph.cox.net with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Wed, 27 Jul 2005 08:11:06 +0200 X-Injected-Via-Gmane: http://gmane.org/ To: gentoo-amd64@lists.gentoo.org From: Duncan <1i5t5.duncan@cox.net> Subject: [gentoo-amd64] Re: amd64 and kernel configuration Date: Tue, 26 Jul 2005 23:10:15 -0700 Organization: Sometimes Message-ID: References: <20050727062947.73020.qmail@mail.mng.mn> Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-Id: Gentoo Linux mail X-BeenThere: gentoo-amd64@gentoo.org Reply-to: gentoo-amd64@lists.gentoo.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Complaints-To: usenet@sea.gmane.org X-Gmane-NNTP-Posting-Host: ip68-230-97-182.ph.ph.cox.net User-Agent: Pan/0.14.2.91 (As She Crawled Across the Table) Sender: news X-Archives-Salt: 8188d4c8-10f5-4b1a-bfa2-292f245db7ae X-Archives-Hash: a30a541083ce71ce77d4f28a85a91294 Dulmandakh Sukhbaatar posted <20050727062947.73020.qmail@mail.mng.mn>, excerpted below, on Wed, 27 Jul 2005 14:29:47 +0800: > I'm new to amd64 and don't know how to configure kernel for best > performance, but I've been using gentoo since 2004.1. Should I enable SMP, > HyperThreading (name differs from hypertransport), and NUMA with single > processor? I found out what with hypertransport performance will better > than without it, but in the help of SMP suggests that if you have single > processor its better to disable SMP. Thus disabling SMP there is no option > for hyperthreading. Last is hyperthreading same as hypertransport or not? > Enabling hyperthreading can i enable hypertransport? Sorry for my poor > english :D. Hypertransport is the name of the interconnect technology AMD uses. It's how the CPU connects to everything else. Therefore, you want that on, or it'll use slower modes. Hyperthreading is an Intel technology, used to help compensate for their very deep CPU pipelining, to minimize the time the CPU spends idle in case of a branch mispredict, by switching to the other thread while the first one goes back to memory to get all the stuff it thought it wouldn't need because it predicted the branch choice wrongly. AMD CPUs don't have such deep pipelining and have other technology to minimize branch mispredict penalties, so don't benefit much from hyperthreading, and therefore don't include it. If your CPU is indeed an AMD64 CPU, you don't want hyperthreading. If it's one of the new Intel x86_64 CPUs, you may or may not want it, depending on which particular one it is and whether hyperthreading is enabled on it or not. SMP is short for Symmetrical Multi-Processing. Traditionally, it meant you had two CPUs. However, hyperthreading is treated by the kernel as two CPUs, which is why SMP must be enabled to get the hyperthreading option. Note that the newest thing to come to x86/x86_64 is dual-core CPUs. These CPUs actually have two logical CPUs in one package. This is better than hyperthreading because it's the real thing. Both Intel and AMD have dual-core units available, but they are quite new and still expensive, so you aren't likely to have one and not know about it. Again, dual core is handled as SMP by the processor, so you'll want SMP on if you have a dual-core CPU. If you are using only a single-core AMD64, you'll want SMP off, because altho the kernel will work with it on, it'll be more bloated than it needs to be. Does that clear up the confusion? -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman in http://www.linuxdevcenter.com/pub/a/linux/2004/12/22/rms_interview.html -- gentoo-amd64@gentoo.org mailing list