Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261559AbUKWWZK (ORCPT ); Tue, 23 Nov 2004 17:25:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261439AbUKWWXk (ORCPT ); Tue, 23 Nov 2004 17:23:40 -0500 Received: from bgm-24-95-139-53.stny.rr.com ([24.95.139.53]:50826 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S261559AbUKWWXD (ORCPT ); Tue, 23 Nov 2004 17:23:03 -0500 Subject: Re: [patch] Real-Time Preemption, -RT-2.6.10-rc2-mm2-V0.7.29-0, and 30-9 From: Steven Rostedt To: Lee Revell Cc: Ingo Molnar , LKML In-Reply-To: <1101246438.1594.3.camel@krustophenia.net> References: <20041123115201.GA26714@elte.hu> <1101244924.32068.6.camel@localhost.localdomain> <1101246438.1594.3.camel@krustophenia.net> Content-Type: text/plain Content-Transfer-Encoding: 7bit Organization: Kihon Technologies Date: Tue, 23 Nov 2004 17:22:55 -0500 Message-Id: <1101248575.32068.11.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1397 Lines: 31 On Tue, 2004-11-23 at 16:47 -0500, Lee Revell wrote: > On Tue, 2004-11-23 at 16:22 -0500, Steven Rostedt wrote: > > Just curious to why you scale the interrupts from 49 down to 25. What > > would be wrong with keeping all of them at 49 (or whatever). Being a > > FIFO, no interrupt would preempt another. Why would you want the first > > IRQs to be registered have higher priority than (and thus will preempt) > > irqs registered later. > > I raised this issue before. I agree that all interrupts should get the > same RT prio by default. Otherwise the default behavior is arbitrary. > > Lee I'll even add that the default behavior slows the system down with extra scheduling switches. If IRQ 10 is preempted by IRQ 2 then there's an extra switch to get back and finish IRQ 10. For every IRQ that comes during a "lower" priority IRQ there's an extra switch needed. If the IRQs really don't have a order of priority, then they should be the same. Some cases you need to set IRQs at different priorities, but that should be done by the user and not the kernel giving the first irq preference. -- Steven Rostedt Senior Engineer Kihon Technologies - 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/