On Fri 16-11-18 15:58:28, Wei Yang wrote: > On Fri, Nov 16, 2018 at 12:26:03PM +0100, Michal Hocko wrote: > >On Fri 16-11-18 12:05:04, osalvador wrote: > >> On Fri, 2018-11-16 at 10:57 +0100, Michal Hocko wrote: > >[...] > >> > E.g. memory hotplug decreases both managed and present counters. I > >> > am actually not sure that is 100% correct (put on my TODO list to > >> > check). There is no consistency in that regards. > >> > >> We can only offline non-reserved pages (so, managed pages). > > > >Yes > > > >> Since present pages holds reserved_pages + managed_pages, decreasing > >> both should be fine unless I am mistaken. > > > >Well, present_pages is defined as "physical pages existing within the zone" > >and those pages are still existing but they are offline. But as I've > >said I have to think about it some more > > I may not catch up with your discussions, while I'd like to share what I > learnt. > > online_pages() > online_pages_range() > zone->present_pages += onlined_pages; > > __offline_pages() > adjust_managed_page_count() > zone->present_pages -= offlined_pages; > > The two counters: present_pages & managed_pages would be adjusted during > online/offline. > > While I am not sure when *reserved_pages* would be adjusted. Will we add > this hot-added memory into memblock.reserved? and allocate memory by > memblock_alloc() after system bootup? This is not really related to this patch. I have only mentioned the memory hotplug as an example. I would rather focus on the change itself so let's not get too off topic here. -- Michal Hocko SUSE Labs
