Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760057AbYCZVkf (ORCPT ); Wed, 26 Mar 2008 17:40:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755382AbYCZVk1 (ORCPT ); Wed, 26 Mar 2008 17:40:27 -0400 Received: from relay1.sgi.com ([192.48.171.29]:53150 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755959AbYCZVk1 (ORCPT ); Wed, 26 Mar 2008 17:40:27 -0400 Date: Wed, 26 Mar 2008 16:40:26 -0500 (CDT) From: Alan Mayer To: Ingo Molnar Cc: Alan Mayer , torvalds@linux-foundation.org, linux-kernel list , Robin Holt , Jack Steiner , Russ Anderson Subject: Re: [PATCH] x86_64: resize NR_IRQS for large machines (re-submit) In-Reply-To: <20080326212312.GA27594@elte.hu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1532 Lines: 51 On Wed, 26 Mar 2008, Ingo Molnar wrote: > > * Alan Mayer wrote: > > > On machines with very large numbers of cpus, tables that are > > dimensioned by NR_IRQS get very large, especially the irq_desc table. > > They are also very sparsely used. When the cpu count is > > > MAX_IO_APICS, use MAX_IO_APICS to set NR_IRQS, otherwise use NR_CPUS. > > thanks Alan, applied this in place of the other patch. > > this bit is still ugly: > > > -#define NR_IRQS (NR_VECTORS + (32 *NR_CPUS)) > > +#if NR_CPUS < MAX_IO_APICS > > +#define NR_IRQS (NR_VECTORS + (32 * NR_CPUS)) > > +#else > > +#define NR_IRQS (NR_VECTORS + (32 * MAX_IO_APICS)) > > +#endif > > #define NR_IRQ_VECTORS NR_IRQS > > but it doesnt really depart from the current status quo of huge > [NR_IRQS] arrays either. Patches that make NR_IRQS a variable are > welcome :) > > Ingo > Good luck with that. If i come up with something that's elegant enough to make it worth the risk, I'll let you know. Changing NR_IRQS to a variable touches every arch and a lot of drivers. Someone is bound to choke on it, so it has to be something worth fighting for. --ajm Lately it occurs to me, What a long, strange trip it's been. -- Alan J. Mayer SGI ajm@sgi.com WORK: 651-683-3131 HOME: 651-407-0134 -- -- 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/