From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47BD55F6.5030203@firstfloor.org> Date: Thu, 21 Feb 2008 11:44:06 +0100 From: Andi Kleen MIME-Version: 1.0 Subject: Re: [PATCH] Document huge memory/cache overhead of memory controller in Kconfig References: <20080220122338.GA4352@basil.nowhere.org> <47BC2275.4060900@linux.vnet.ibm.com> <200802211535.38932.nickpiggin@yahoo.com.au> <47BD06C2.5030602@linux.vnet.ibm.com> In-Reply-To: <47BD06C2.5030602@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: balbir@linux.vnet.ibm.com Cc: Nick Piggin , akpm@osdl.org, torvalds@osdl.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: > 1. We could create something similar to mem_map, we would need to handle 4 4? At least x86 mainline only has two ways now. flatmem and vmemmap. > different ways of creating mem_map. Well it would be only a single way to create the "aux memory controller map" (or however it will be called). Basically just a call to single function from a few different places. > 2. On x86 with 64 GB ram, First i386 with 64GB just doesn't work, at least not with default 3:1 split. Just calculate it yourself how much of the lowmem area is left after the 64GB mem_map is allocated. Typical rule of thumb is that 16GB is the realistic limit for 32bit x86 kernels. Worrying about anything more does not make much sense. > if we decided to use vmalloc space, we would need 64 > MB of vmalloc'ed memory Yes and if you increase mem_map you need exactly the same space in lowmem too. So increasing the vmalloc reservation for this is equivalent. Just make sure you use highmem backed vmalloc. -Andi -- 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