Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932223AbWHGSzA (ORCPT ); Mon, 7 Aug 2006 14:55:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932307AbWHGSzA (ORCPT ); Mon, 7 Aug 2006 14:55:00 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:26331 "EHLO ebiederm.dsl.xmission.com") by vger.kernel.org with ESMTP id S932223AbWHGSzA (ORCPT ); Mon, 7 Aug 2006 14:55:00 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Andrew Morton Cc: "Randy.Dunlap" , Andi Kleen , "Protasevich, Natalie" , Subject: [PATCH] x86_64: Make NR_IRQS configurable in Kconfig In-Reply-To: <20060807105537.08557636.rdunlap@xenotime.net> (Randy Dunlap's message of "Mon, 7 Aug 2006 10:55:37 -0700") References: <20060807085924.72f832af.rdunlap@xenotime.net> <20060807105537.08557636.rdunlap@xenotime.net> User-Agent: Gnus/5.110004 (No Gnus v0.4) Emacs/21.4 (gnu/linux) Date: Mon, 07 Aug 2006 12:53:35 -0600 Message-ID: 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: 2731 Lines: 76 Currently on a SMP system we can theoretically support NR_CPUS*224 irqs. Unfortunately our data structures don't cope will with that many irqs, nor does hardware typically provide that many irq sources. With the number of cores starting to follow Moore's Law, and the apicid limits being raised beyond an 8bit number trying to track our current maximum with our current data structures would be fatal and wasteful. So this patch decouples the number of irqs we support from the number of cpus. We can revisit this decision once someone reworks the current data structures. This version has my stupid typos fix and the true maximum exposed to make it clear that I have a low default. The worst that I can see happening is there won't be any per_cpu space left for modules if someone sets this too high, but the system should still boot. For non-SMP systems the default is set to 224 IRQs. Signed-off-by: Eric W. Biederman --- arch/x86_64/Kconfig | 14 ++++++++++++++ include/asm-x86_64/irq.h | 3 ++- 2 files changed, 16 insertions(+), 1 deletions(-) diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig index 7598d99..c87b0bc 100644 --- a/arch/x86_64/Kconfig +++ b/arch/x86_64/Kconfig @@ -384,6 +384,20 @@ 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 (224-57344)" + range 224 57344 + default "4096" if SMP + default "224" if !SMP + help + This allows you to specify the maximum number of IRQs which this + kernel will support. Current default is 4096 IRQs as that + is slightly larger than has observed in the field. Setting + a noticeably larger value will exhaust your per cpu memory, + and waste memory in the per irq arrays. + + If unsure leave this at the default. + config HOTPLUG_CPU bool "Support for hot-pluggable CPUs (EXPERIMENTAL)" depends on SMP && HOTPLUG && EXPERIMENTAL diff --git a/include/asm-x86_64/irq.h b/include/asm-x86_64/irq.h index 5006c6e..34b264a 100644 --- a/include/asm-x86_64/irq.h +++ b/include/asm-x86_64/irq.h @@ -31,7 +31,8 @@ #define NR_VECTORS 256 #define FIRST_SYSTEM_VECTOR 0xef /* duplicated in hw_irq.h */ -#define NR_IRQS (NR_VECTORS + (32 *NR_CPUS)) +/* We can use at most NR_CPUS*224 irqs at one time */ +#define NR_IRQS (CONFIG_NR_IRQS) #define NR_IRQ_VECTORS NR_IRQS static __inline__ int irq_canonicalize(int irq) -- 1.4.2.rc3.g7e18e - 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/