From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 26 Mar 2008 18:55:54 +0200 From: Adrian Bunk Subject: Re: [PATCH 2/2] x86: Modify Kconfig to allow up to 4096 cpus Message-ID: <20080326165554.GD1789@cs181133002.pp.htv.fi> References: <20080326014137.934171000@polaris-admin.engr.sgi.com> <20080326014138.292294000@polaris-admin.engr.sgi.com> <20080326160924.GC1789@cs181133002.pp.htv.fi> <47EA7A5A.5030207@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <47EA7A5A.5030207@sgi.com> Sender: owner-linux-mm@kvack.org Return-Path: To: Mike Travis Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, Mar 26, 2008 at 09:31:22AM -0700, Mike Travis wrote: > Adrian Bunk wrote: > > On Tue, Mar 25, 2008 at 06:41:39PM -0700, Mike Travis wrote: > >> Increase the limit of NR_CPUS to 4096 and introduce a boolean > >> called "MAXSMP" which when set (e.g. "allyesconfig"), will set > >> NR_CPUS = 4096 and NODES_SHIFT = 9 (512). > > > > > > I'm not really getting the point of MAXSMP - people should simply pick > > their values, and when they want the maximum "(2-4096)" and "(1-15)" > > already provide this information (except that your patch hides the > > latter information from the user). > > > > And with your patch, even with MAXSMP=y people could still set > > NR_CPUS=7 and NODES_SHIFT=15 or whatever else they want... > > > > More interesting would be why you want it to set NODES_SHIFT to > > something less than the maximum value of 15. I'm getting the fact that > > 2^15 > 4096 and that 15 might be nonsensical high, but this sounds more > > like requiring a patch to limit the range to 9? > > I guess the main effect is that "MAXSMP" represents what's really > usable for an architecture based on other factors. The limit of > NODES_SHIFT = 15 is that it's represented in some places as a signed > 16-bit value, so 15 is the hard limit without coding changes, not > an architecture limit. This is the x86-specific Kconfig file that presents the x86 specific limits to the users. If NODES_SHIFT=15 is offered to the user although it's higher than the current architecture limit on x86 then this is simply a bug that should be fixed. > Thanks, > Mike cu Adrian -- "Is there not promise of rain?" Ling Tan asked suddenly out of the darkness. There had been need of rain for many days. "Only a promise," Lao Er said. Pearl S. Buck - Dragon Seed -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org