Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268739AbUILOUp (ORCPT ); Sun, 12 Sep 2004 10:20:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268742AbUILOUp (ORCPT ); Sun, 12 Sep 2004 10:20:45 -0400 Received: from mail-relay-2.tiscali.it ([213.205.33.42]:46494 "EHLO mail-relay-2.tiscali.it") by vger.kernel.org with ESMTP id S268739AbUILOUl (ORCPT ); Sun, 12 Sep 2004 10:20:41 -0400 Date: Sun, 12 Sep 2004 16:17:01 +0200 From: Andrea Arcangeli To: Arjan van de Ven Cc: Hugh Dickins , "Martin J. Bligh" , Andrea Arcangeli , Alan Cox , Chris Wedgwood , LKML , Christoph Hellwig Subject: Re: [PATCH 1/3] Separate IRQ-stacks from 4K-stacks option Message-ID: <20040912141701.GA21626@nocona.random> References: <593560000.1094826651@[10.10.2.4]> <20040910151538.GA24434@devserv.devel.redhat.com> <20040910152852.GC15643@x30.random> <20040910153421.GD24434@devserv.devel.redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040910153421.GD24434@devserv.devel.redhat.com> X-GPG-Key: 1024D/68B9CB43 13D9 8355 295F 4823 7C49 C012 DFA1 686E 68B9 CB43 X-PGP-Key: 1024R/CB4660B9 CC A0 71 81 F4 A0 63 AC C0 4B 81 1D 8C 15 C8 E5 User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1181 Lines: 22 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. > time, but when they nest you effectively have like a semi context switch in > the middle of the work so performance suffers... It's not nearly a semi context switch, it's like the timer irq that runs on top of userspace, not nearly the cost of a context switch (no time wasted calling the scheduler or the softirqs either for obvious reasons). - 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/