From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 559908D003B for ; Fri, 22 Apr 2011 16:35:55 -0400 (EDT) Subject: Re: [PATCH v3] mm: make expand_downwards symmetrical to expand_upwards From: James Bottomley 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 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: 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 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, 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org