From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261227AbVFKEgq (ORCPT ); Sat, 11 Jun 2005 00:36:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261246AbVFKEgp (ORCPT ); Sat, 11 Jun 2005 00:36:45 -0400 Received: from mx2.elte.hu ([157.181.151.9]:14032 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S261227AbVFKEgo (ORCPT ); Sat, 11 Jun 2005 00:36:44 -0400 Date: Sat, 11 Jun 2005 06:32:31 +0200 From: Ingo Molnar To: Esben Nielsen Cc: Gabor MICSKO , linux-kernel@vger.kernel.org Subject: Re: hackbench: 2.6.12-rc6 vs. 2.6.12-rc6-RT-V0.7.48-06 Message-ID: <20050611043231.GA16500@elte.hu> References: <1118436975.1702.11.camel@alderaan.trey.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Esben Nielsen wrote: > Depends on the configuration options. If you used the same configs > they should be the same but if you activated PREEMPT_RT it should slow > things down due to the overhead of irq-threading and mutexes instead > of spinlocks - although I am surprised the factor is _that_ big! one has to make sure the default debug options are disabled. (DEADLOCK_DETECT, PREEMPT_DEBUG, etc.) But even then there will be considerable overhead. Until recently, the overhead used to be even bigger. Note that hackbench is pretty much the worst-case for PREEMPT_RT: lots of locking and scheduling done and we compare the UP kernel to the SMP kernel in essence. (in fact PREEMPT_RT's locking is currently higher overhead than SMP) Ingo