From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 143448D003B for ; Fri, 22 Apr 2011 16:24:56 -0400 (EDT) Received: from d01relay07.pok.ibm.com (d01relay07.pok.ibm.com [9.56.227.147]) by e7.ny.us.ibm.com (8.14.4/8.13.1) with ESMTP id p3MK2aGr025374 for ; Fri, 22 Apr 2011 16:02:36 -0400 Received: from d01av04.pok.ibm.com (d01av04.pok.ibm.com [9.56.224.64]) by d01relay07.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p3MKOq6W1097906 for ; Fri, 22 Apr 2011 16:24:52 -0400 Received: from d01av04.pok.ibm.com (loopback [127.0.0.1]) by d01av04.pok.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p3MKOp1u030839 for ; Fri, 22 Apr 2011 16:24:52 -0400 Subject: Re: [PATCH v3] mm: make expand_downwards symmetrical to expand_upwards From: Dave Hansen In-Reply-To: <1303496357.2590.38.camel@mulgrave.site> 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> Content-Type: text/plain; charset="ISO-8859-1" Date: Fri, 22 Apr 2011 13:24:48 -0700 Message-ID: <1303503888.9308.6661.camel@nimitz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: James Bottomley 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 13:19 -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. :( 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. -- Dave -- 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