From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Fri, 3 May 2019 09:35:50 +0200 From: Oscar Salvador Subject: Re: [PATCH v7 01/12] mm/sparsemem: Introduce struct mem_section_usage Message-ID: <20190503073550.GB15740@linux> References: <155677652226.2336373.8700273400832001094.stgit@dwillia2-desk3.amr.corp.intel.com> <155677652762.2336373.6522945152928524695.stgit@dwillia2-desk3.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <155677652762.2336373.6522945152928524695.stgit@dwillia2-desk3.amr.corp.intel.com> Sender: owner-linux-mm@kvack.org To: Dan Williams Cc: akpm@linux-foundation.org, Michal Hocko , Vlastimil Babka , Logan Gunthorpe , linux-nvdimm@lists.01.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, May 01, 2019 at 10:55:27PM -0700, Dan Williams wrote: > Towards enabling memory hotplug to track partial population of a > section, introduce 'struct mem_section_usage'. > > A pointer to a 'struct mem_section_usage' instance replaces the existing > pointer to a 'pageblock_flags' bitmap. Effectively it adds one more > 'unsigned long' beyond the 'pageblock_flags' (usemap) allocation to > house a new 'map_active' bitmap. The new bitmap enables the memory > hot{plug,remove} implementation to act on incremental sub-divisions of a > section. > > The primary motivation for this functionality is to support platforms > that mix "System RAM" and "Persistent Memory" within a single section, > or multiple PMEM ranges with different mapping lifetimes within a single > section. The section restriction for hotplug has caused an ongoing saga > of hacks and bugs for devm_memremap_pages() users. > > Beyond the fixups to teach existing paths how to retrieve the 'usemap' > from a section, and updates to usemap allocation path, there are no > expected behavior changes. > > Cc: Michal Hocko > Cc: Vlastimil Babka > Cc: Logan Gunthorpe > Signed-off-by: Dan Williams Reviewed-by: Oscar Salvador -- Oscar Salvador SUSE L3