Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756652Ab1DVUf4 (ORCPT ); Fri, 22 Apr 2011 16:35:56 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:46869 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756418Ab1DVUfx (ORCPT ); Fri, 22 Apr 2011 16:35:53 -0400 Subject: Re: [PATCH v3] mm: make expand_downwards symmetrical to expand_upwards From: James Bottomley To: Dave Hansen Cc: Christoph Lameter , KOSAKI Motohiro , David Rientjes , Pekka Enberg , Michal Hocko , Andrew Morton , Hugh Dickins , linux-mm@kvack.org, LKML , linux-parisc@vger.kernel.org, Ingo Molnar , x86 maintainers , Tejun Heo , Mel Gorman In-Reply-To: <1303503888.9308.6661.camel@nimitz> References: <1303337718.2587.51.camel@mulgrave.site> <20110421221712.9184.A69D9226@jp.fujitsu.com> <1303403847.4025.11.camel@mulgrave.site> <1303411537.9048.3583.camel@nimitz> <1303496357.2590.38.camel@mulgrave.site> <1303503888.9308.6661.camel@nimitz> Content-Type: text/plain; charset="UTF-8" Date: Fri, 22 Apr 2011 15:35:50 -0500 Message-ID: <1303504550.2590.43.camel@mulgrave.site> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1832 Lines: 38 On Fri, 2011-04-22 at 13:24 -0700, Dave Hansen wrote: > On Fri, 2011-04-22 at 13:19 -0500, James Bottomley wrote: > > I looked at converting parisc to sparsemem and there's one problem that > > none of these cover. How do you set up bootmem? If I look at the > > examples, they all seem to have enough memory in the first range to > > allocate from, so there's no problem. On parisc, with discontigmem, we > > set up all of our ranges as bootmem (we can do this because we > > effectively have one node per range). Obviously, since sparsemem has a > > single bitmap for all of the bootmem, we can no longer allocate all of > > our memory to it (well, without exploding because some of our gaps are > > gigabytes big). How does everyone cope with this (do you search for > > your largest range and use that as bootmem or something)? > > Sparsemem is purely post-bootmem. It doesn't deal with sparse > bootmem. :( Well, this is enabled in discontigmem, sigh. > That said, I'm not sure you're in trouble. One bit of bitmap covers 4k > (with 4k pages of course) of memory, one byte covers 32k, and A 32MB > bitmap can cover 1TB of address space. It explodes, but I think it's > manageable. It hasn't been a problem enough up to this point to go fix > it. I think the platform limited physical address range is 42 bits, so I suppose that's 128MB ... hopefully we should have that as a contiguous range from the end of the loaded kernel. We're lucky they didn't enable the full ZX1 address range; that would have been 48 bits (or a whole gigabyte just for the bitmap). James -- 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/