On 08/01/2018 02:23 PM, osalvador@xxxxxxxxxxxxxxxxxx wrote: > From: Oscar Salvador <osalvador@xxxxxxx> > > Currently, whenever a new node is created/re-used from the memhotplug path, > we call free_area_init_node()->free_area_init_core(). > But there is some code that we do not really need to run when we are coming > from such path. > > free_area_init_core() performs the following actions: > > 1) Initializes pgdat internals, such as spinlock, waitqueues and more. > 2) Account # nr_all_pages and # nr_kernel_pages. These values are used later on > when creating hash tables. > 3) Account number of managed_pages per zone, substracting dma_reserved and memmap pages. > 4) Initializes some fields of the zone structure data > 5) Calls init_currently_empty_zone to initialize all the freelists > 6) Calls memmap_init to initialize all pages belonging to certain zone > > When called from memhotplug path, free_area_init_core() only performs actions #1 and #4. > > Action #2 is pointless as the zones do not have any pages since either the node was freed, > or we are re-using it, eitherway all zones belonging to this node should have 0 pages. > For the same reason, action #3 results always in manages_pages being 0. > > Action #5 and #6 are performed later on when onlining the pages: > online_pages()->move_pfn_range_to_zone()->init_currently_empty_zone() > online_pages()->move_pfn_range_to_zone()->memmap_init_zone() > > This patch does two things: > > First, moves the node/zone initializtion to their own function, so it allows us > to create a small version of free_area_init_core, where we only perform: > > 1) Initialization of pgdat internals, such as spinlock, waitqueues and more > 4) Initialization of some fields of the zone structure data > > These two functions are: pgdat_init_internals() and zone_init_internals(). > > The second thing this patch does, is to introduce free_area_init_core_hotplug(), > the memhotplug version of free_area_init_core(): > > Currently, we call free_area_init_node() from the memhotplug path. > In there, we set some pgdat's fields, and call calculate_node_totalpages(). > calculate_node_totalpages() calculates the # of pages the node has. > > Since the node is either new, or we are re-using it, the zones belonging to > this node should not have any pages, so there is no point to calculate this now. > > Actually, we re-set these values to 0 later on with the calls to: > > reset_node_managed_pages() > reset_node_present_pages() > > The # of pages per node and the # of pages per zone will be calculated when > onlining the pages: > > online_pages()->move_pfn_range()->move_pfn_range_to_zone()->resize_zone_range() > online_pages()->move_pfn_range()->move_pfn_range_to_zone()->resize_pgdat_range() > > Also, with this change, only pgdat_init_internals() and zone_init_internals() should > be kept around after initialization, since they can be called from memory-hotplug > code. > So let us reconvert all the other functions from __meminit to __init, as we do not need > them after initialization: > > zero_resv_unavail > set_pageblock_order > calc_memmap_size > free_area_init_core > free_area_init_node > > Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> > Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> > Acked-by: Michal Hocko <mhocko@xxxxxxxx> Yep, it's safer to only do the actions relevant to hotplug during hotplug. Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
