Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268081AbUILPkq (ORCPT ); Sun, 12 Sep 2004 11:40:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268114AbUILPkq (ORCPT ); Sun, 12 Sep 2004 11:40:46 -0400 Received: from dragnfire.mtl.istop.com ([66.11.160.179]:17151 "EHLO dsl.commfireservices.com") by vger.kernel.org with ESMTP id S268081AbUILPko (ORCPT ); Sun, 12 Sep 2004 11:40:44 -0400 Date: Sun, 12 Sep 2004 11:45:19 -0400 (EDT) From: Zwane Mwaikambo To: "Martin J. Bligh" Cc: Andrea Arcangeli , Arjan van de Ven , Hugh Dickins , Andrea Arcangeli , Alan Cox , Chris Wedgwood , LKML , Christoph Hellwig Subject: Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option In-Reply-To: <622230000.1095001434@[10.10.2.4]> Message-ID: References: <593560000.1094826651@[10.10.2.4]> <20040910151538.GA24434@devserv.devel.redhat.com> <20040910152852.GC15643@x30.random> <20040910153421.GD24434@devserv.devel.redhat.com> <20040912141701.GA21626@nocona.random> <622230000.1095001434@[10.10.2.4]> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1744 Lines: 34 yOn Sun, 12 Sep 2004, Martin J. Bligh wrote: > --Andrea Arcangeli wrote (on Sunday, September 12, 2004 16:17:01 +0200): > > > On Fri, Sep 10, 2004 at 05:34:21PM +0200, Arjan van de Ven wrote: > >> disabling is actually not a bad idea; hard irq handlers run for a very short > > > > you mean hard irq handlers "should run" for a very short time. There can > > be slow hardware that needs a long time, and fast hardware that needs a > > short time, and in turn it makes perfect sense to allow nesting to give > > low latency to the "fast" onces, like it has always happened so far (not > > only in linux AFIK). Disabling nesting completely sounds a very bad > > idea to me, when "limiting nesting" can be achieved easily as confirmed > > by Alan too. > > IIRC, what we did in PTX was have 16 SPL levels, each interrupt was assigned > a prio, and higher prio interrupts could interrupt lower prio ones (but not > the same prio or higher). There's some support for that in the APIC, I think, > something like the high nybble is prio, and the low nybble is just an index. Currently we do use priorities on i386/APIC, albeit unintentionally by assigning higher IRQs higher vectors resulting in a higher priority. However interrupt priorities on non deterministic general purpose operating systems seems pointless for the vast majority of the devices plugged into boxes these days. Not to mention possible starvation issues from high frequency long running interrupts. Zwane - 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/