Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268120AbUILQBY (ORCPT ); Sun, 12 Sep 2004 12:01:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268121AbUILQBY (ORCPT ); Sun, 12 Sep 2004 12:01:24 -0400 Received: from jade.spiritone.com ([216.99.193.136]:45249 "EHLO jade.spiritone.com") by vger.kernel.org with ESMTP id S268120AbUILQBW (ORCPT ); Sun, 12 Sep 2004 12:01:22 -0400 Date: Sun, 12 Sep 2004 09:00:51 -0700 From: "Martin J. Bligh" To: Zwane Mwaikambo 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 Message-ID: <623470000.1095004850@[10.10.2.4]> In-Reply-To: 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]> X-Mailer: Mulberry/2.2.1 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2075 Lines: 41 --Zwane Mwaikambo wrote (on Sunday, September 12, 2004 11:45:19 -0400): > 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. Well, the idea is that long running interrupts get low prios ;-) But yes, we're fairly non-deterministic, apart from the timer interrupt, etc which are at one end of the scale, though I forget which ;-) M. - 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/