Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932209AbVIMVMW (ORCPT ); Tue, 13 Sep 2005 17:12:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932504AbVIMVMW (ORCPT ); Tue, 13 Sep 2005 17:12:22 -0400 Received: from ncc1701.cistron.net ([62.216.30.38]:31120 "EHLO ncc1701.cistron.net") by vger.kernel.org with ESMTP id S932209AbVIMVMV (ORCPT ); Tue, 13 Sep 2005 17:12:21 -0400 From: dth@cistron.nl (Danny ter Haar) Subject: Q: why _less_ performance on machine with SMP then with UP kernel ? Date: Tue, 13 Sep 2005 21:12:15 +0000 (UTC) Organization: Cistron Message-ID: X-Trace: ncc1701.cistron.net 1126645935 5551 62.216.30.70 (13 Sep 2005 21:12:15 GMT) X-Complaints-To: abuse@cistron.nl X-Newsreader: trn 4.0-test76 (Apr 2, 2001) Originator: dth@cistron.nl (Danny ter Haar) To: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1681 Lines: 43 I've been posting here recently bout our newsgateway. For short: If i enable both CPU's i get less performance than enabling both cpu's Long version: Here is a description of the setup: --- It's a tyan server /motherboard http://www.tyan.com/products/html/ta26b2882.html with 2 x OPTERON250 cpu's and 4 GIG of ECC ram. There is 8 x scsi disks for storage cupper gig-E for internal communication to spool/header servers etc. acenic FiberOptic Gig-E 64bit PCI card for link to the internet. Bandwidth use is sampled from the ethernet switch and with mrtg visualised. Take today for example: http://newsgate.newsserver.nl/kernel/2.6.14-rc1-ethernet-bandwidth.png >From yesterday till 10:30am i ran 2.6.13.1 in UP mode. As you can see blue (==incoming traffic) is fairly constant. This morning i compiled/installed 2.6.14-rc1-smp. I let it ran till 12:15 but it's clear that it can't keep up with the flow of data. I rebooted to 2.6.14-rc1 (UP) and that keeps up with the data just fine. So what is the difference between UP & SMP ? shared memory , shared interrupts. I don't know _why_ it's living up to _my_ expectation. I hoped that the load would drop (it's between 4 to 5) op UP kernel because certain processes would be split over the processors. Anybody want to try and explain to me where i'm making an error ? Config file & kern.log output can be found at : http://newsgate.newsserver.nl/kernel/ A very confused Danny - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/