Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 29 Jul 2002 15:59:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 29 Jul 2002 15:59:20 -0400 Received: from mg02.austin.ibm.com ([192.35.232.12]:26581 "EHLO mg02.austin.ibm.com") by vger.kernel.org with ESMTP id convert rfc822-to-8bit; Mon, 29 Jul 2002 15:59:18 -0400 Content-Type: text/plain; charset="us-ascii" From: Andrew Theurer To: linux-kernel@vger.kernel.org Subject: Re: Linux 2.4.19-rc3 (hyperthreading) Date: Mon, 29 Jul 2002 14:54:30 -0500 X-Mailer: KMail [version 1.4] Cc: Marcelo Tosatti MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT Message-Id: <200207291454.30076.habanero@us.ibm.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1588 Lines: 33 I would caution against having hyperthreading on by default in the 2.4.19 release. I am seeing a significant degrade in network workloads on P4 with hyperthreading on. On 2.4.19-pre10, I get 788 Mbps on NetBench, but on 2.4.19-rc1 (and probably rc3, should know in an hour), I get 690 Mbps. It is clearly a hyperthreading/interrupt routing issue. On this system (4 x P4), with no hyperthreading, there is enough CPU to handle all interrupts on CPU0 (this is where all ints go by default). With hyperthreading on, I get "1/2" of a CPU for interrupt processing. What ends up happenning is that CPU0 is at 100%, while CPU1-CPU7 are at 75%. Now I know the "noth" is available, but since hyperthreading is not proven to give a performance boost to more than 1/2 of the common workloads for linux users (or is it? who has done tests?), I'd like to see this default behavior reversed, and still use acpismp=force to enable hyperthreading. Also, If anyone has performance results for their workloads showing a boost with hyperthreading, I would really like to know. -Andrew Theurer <rc3 changelog only because the full changelog got too big (I guess thats why my -rc2 announce mail didnt go to lk).>> - 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/