Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932130AbWHGQpU (ORCPT ); Mon, 7 Aug 2006 12:45:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932123AbWHGQpU (ORCPT ); Mon, 7 Aug 2006 12:45:20 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:54999 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S932130AbWHGQpT (ORCPT ); Mon, 7 Aug 2006 12:45:19 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: "Randy.Dunlap" Cc: Andrew Morton , Andi Kleen , "Protasevich, Natalie" , Subject: Re: [PATCH] x86_64: Make NR_IRQS configurable in Kconfig References: <20060807085924.72f832af.rdunlap@xenotime.net> Date: Mon, 07 Aug 2006 10:44:00 -0600 In-Reply-To: <20060807085924.72f832af.rdunlap@xenotime.net> (Randy Dunlap's message of "Mon, 7 Aug 2006 08:59:24 -0700") Message-ID: User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) 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: 1823 Lines: 45 "Randy.Dunlap" writes: >> diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig >> index 7598d99..d744e5b 100644 >> --- a/arch/x86_64/Kconfig >> +++ b/arch/x86_64/Kconfig >> @@ -384,6 +384,19 @@ config NR_CPUS >> This is purely to save memory - each supported CPU requires >> memory in the static kernel configuration. >> >> +config NR_IRQS >> + int "Maximum number of IRQs (224-4096)" >> + range 256 4096 >> + depends on SMP >> + default "4096" >> + help >> + This allows you to specify the maximum number of IRQs which this >> + kernel will support. Current maximum is 4096 IRQs as that >> + is slightly larger than has observed in the field. >> + >> + This is purely to save memory - each supported IRQ requires >> + memory in the static kernel configuration. > > If (a) "nor does hardware typically provide that many irq sources" > and (b) "This is purely to save memory", why is the default > 4096 instead of something smaller? a) Because I would like to flush out bugs. b) Because I want a default that works for everyone. c) Because with MSI we have a potential for large irq counts on most systems. d) Because anyone who disagrees with me can send a patch and fix the default. e) Because with the default number of cpus we can very close to needing this many irqs in the worst case. f) This is much better than previous to my patch and setting NR_CPUS=255 and getting 8K IRQS. g) Because I probably should have been more inventive than copying the NR_IRQS text, but when I did the wording sounded ok to me. Eric - 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/