Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262021AbUK3IuJ (ORCPT ); Tue, 30 Nov 2004 03:50:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262022AbUK3IuJ (ORCPT ); Tue, 30 Nov 2004 03:50:09 -0500 Received: from mx2.elte.hu ([157.181.151.9]:58850 "EHLO mx2.elte.hu") by vger.kernel.org with ESMTP id S262021AbUK3Itq (ORCPT ); Tue, 30 Nov 2004 03:49:46 -0500 Date: Tue, 30 Nov 2004 09:49:04 +0100 From: Ingo Molnar To: Esben Nielsen Cc: linux-kernel@vger.kernel.org Subject: Re: Priority Inheritance Test (Real-Time Preemption) Message-ID: <20041130084904.GA17799@elte.hu> References: <20041129155752.GA17828@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.1i 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, autolearn=not spam, 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 Content-Length: 1586 Lines: 49 * Esben Nielsen wrote: > > and i'm regularly testing this property with 'hackbench 50', which > > creates over a 1000 wildly scheduling non-RT tasks. Latency is not > > affected by such workloads. > > > > Probably not. Even while doing that you most likely wont build up wait > lists of more than 10, maybe 100 tasks? Doing full traversals with irq > disabled probably wont be meassureable!(?) compared to much other > stuff increasing responsible for the meassured latency. there is no full list traversal of SCHED_NORMAL tasks, ever. but the best way is to test this yourself, download Florian's rtc_wakeup from: http://www.affenbande.org/~tapas/wiki/index.php?rtc_wakeup and run it with the highest possible resolution, 8192 Hz: chrt -f 98 -p `pidof 'IRQ 8'` chrt -f 99 -p `pidof 'IRQ 0'` ./rtc_wakeup -f 8192 -t 100000 in this mode rtc_wakeup will report the worst irq-delivery latency it measures. It will thus measure the combined effect of any type of scheduling or irqs-off latency to RT-tasks. then download hackbench from: http://developer.osdl.org/craiger/hackbench/ and try e.g.: ./hackbench 50 this will start 2x20x50 == 2000 SCHED_NORMAL threads, all performing a nice pattern of scheduling simulating a busy chat server workload with tons of messages going back and forth. Ingo - 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/