From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47EBB802.7000801@sgi.com> Date: Thu, 27 Mar 2008 08:06:42 -0700 From: Mike Travis MIME-Version: 1.0 Subject: Re: [PATCH 2/2] x86: Modify Kconfig to allow up to 4096 cpus 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> <20080326165554.GD1789@cs181133002.pp.htv.fi> In-Reply-To: <20080326165554.GD1789@cs181133002.pp.htv.fi> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Adrian Bunk Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: Adrian Bunk wrote: > 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 > Ok, I'll modify it in the next version. Thanks! Mike -- 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