Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751867AbbHNWdQ (ORCPT ); Fri, 14 Aug 2015 18:33:16 -0400 Received: from mail-ig0-f170.google.com ([209.85.213.170]:32909 "EHLO mail-ig0-f170.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751102AbbHNWdO (ORCPT ); Fri, 14 Aug 2015 18:33:14 -0400 MIME-Version: 1.0 In-Reply-To: <20150814220605.GB3265@gmail.com> References: <20150813031253.36913.29580.stgit@otcpl-skl-sds-2.jf.intel.com> <20150813035005.36913.77364.stgit@otcpl-skl-sds-2.jf.intel.com> <20150814213714.GA3265@gmail.com> <20150814220605.GB3265@gmail.com> Date: Fri, 14 Aug 2015 15:33:13 -0700 Message-ID: Subject: Re: [RFC PATCH 1/7] x86, mm: ZONE_DEVICE for "device memory" From: Dan Williams To: Jerome Glisse Cc: "linux-kernel@vger.kernel.org" , Boaz Harrosh , Rik van Riel , "linux-nvdimm@lists.01.org" , Dave Hansen , david , Ingo Molnar , Linux MM , Ingo Molnar , Mel Gorman , "H. Peter Anvin" , Ross Zwisler , "torvalds@linux-foundation.org" , Christoph Hellwig Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1340 Lines: 30 On Fri, Aug 14, 2015 at 3:06 PM, Jerome Glisse wrote: > On Fri, Aug 14, 2015 at 02:52:15PM -0700, Dan Williams wrote: >> On Fri, Aug 14, 2015 at 2:37 PM, Jerome Glisse wrote: >> > On Wed, Aug 12, 2015 at 11:50:05PM -0400, Dan Williams wrote: [..] >> > What is the rational for not updating max_pfn, max_low_pfn, ... ? >> > >> >> The idea is that this memory is not meant to be available to the page >> allocator and should not count as new memory capacity. We're only >> hotplugging it to get struct page coverage. > > But this sounds bogus to me to rely on max_pfn to stay smaller than > first_dev_pfn. For instance you might plug a device that register > dev memory and then some regular memory might be hotplug, effectively > updating max_pfn to a value bigger than first_dev_pfn. > True. > Also i do not think that the buddy allocator use max_pfn or max_low_pfn > to consider page/zone for allocation or not. Yes, I took it out with no effects. I'll investigate further whether we should be touching those variables or not for this new usage. -- 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/