Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262279AbUILVgf (ORCPT ); Sun, 12 Sep 2004 17:36:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262605AbUILVgf (ORCPT ); Sun, 12 Sep 2004 17:36:35 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:60549 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S262279AbUILVgd (ORCPT ); Sun, 12 Sep 2004 17:36:33 -0400 Subject: Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option From: Lee Revell To: Andrea Arcangeli Cc: Ingo Molnar , Chris Wedgwood , Arjan van de Ven , Hugh Dickins , "Martin J. Bligh" , Alan Cox , LKML , Christoph Hellwig In-Reply-To: <20040912203308.GA3049@dualathlon.random> References: <593560000.1094826651@[10.10.2.4]> <20040910151538.GA24434@devserv.devel.redhat.com> <20040910152852.GC15643@x30.random> <20040910153421.GD24434@devserv.devel.redhat.com> <1095016687.1306.667.camel@krustophenia.net> <20040912192515.GA8165@taniwha.stupidest.org> <20040912193542.GB28791@elte.hu> <20040912203308.GA3049@dualathlon.random> Content-Type: text/plain Message-Id: <1095025000.22893.52.camel@krustophenia.net> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Sun, 12 Sep 2004 17:36:41 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1493 Lines: 38 On Sun, 2004-09-12 at 16:33, Andrea Arcangeli wrote: > On Sun, Sep 12, 2004 at 09:35:42PM +0200, Ingo Molnar wrote: > > no. A 2 msec nonpreemptable delay is a 2 msec delay, irqs on or off > > alike. > > irq-latency is an order of magnitude higher prio, than the scheduler > latency. above you only talk about scheduler latency. > But in this case the hardirq handler can run for 2ms, which caused a scheduler latency problem, because nothing could run but other IRQs. The IRQ threading in Ingo's patches solves the problem, and seems to me to be the correct solution. > hence I don't think not allowing nested irqs at all is a good idea and > it's a nice feature to support them. Agreed. I was just pointing out that in addition to being a bad idea it wouldn't work unless the IDE i/o completion issue is addressed. The issue IIRC was the potential for stack overflow with 4K stacks if we get deeply nested IRQs. I believe the VP patches allow you to see the IRQ nesting in the logs, you could probably grep the logs for these incidents. Seems like you could test the stack overflow theory by setting up a stream of interrupts from the sound card and RTC to coincide with the timer interrupt, then stressing the disks and network. Lee - 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/