On 05/23/2017 04:49 PM, Reza Arbab wrote: > On Tue, May 23, 2017 at 03:05:08PM -0500, Michael Bringmann wrote: >> On 05/23/2017 10:52 AM, Reza Arbab wrote: >>> On Tue, May 23, 2017 at 10:15:44AM -0500, Michael Bringmann wrote: >>>> +static void setup_nodes(void) >>>> +{ >>>> + int i, l = 32 /* MAX_NUMNODES */; >>>> + >>>> + for (i = 0; i < l; i++) { >>>> + if (!node_possible(i)) { >>>> + setup_node_data(i, 0, 0); >>>> + node_set(i, node_possible_map); >>>> + } >>>> + } >>>> +} >>> >>> This seems to be a workaround for 3af229f2071f ("powerpc/numa: Reset >>> node_possible_map to only node_online_map"). >> >> They may be related, but that commit is not a replacement. The above patch >> ensures that >> there are enough of the nodes initialized at startup to allow for memory >> hot-add into a >> node that was not used at boot. (See 'setup_node_data' function in >> 'numa.c'.) That and >> recording that the node was initialized. > > Is it really necessary to preinitialize these empty nodes using > setup_node_data()? When you do memory hotadd into a node that was not used at > boot, the node data already gets set up by > > add_memory > add_memory_resource > hotadd_new_pgdat > arch_alloc_nodedata <-- allocs the pg_data_t > ... > free_area_init_node <-- sets NODE_DATA(nid)->node_id, etc.
I see that code now, but for some reason it did not work when I hot-added memory. > > Removing setup_node_data() from that loop leaves only the call to node_set(). > If 3af229f2071f (which reduces node_possible_map) was reverted, you wouldn't > need to do that either. > >> I didn't see where any part of commit 3af229f2071f would touch the >> 'node_possible_map' >> which is needed by 'numa.c' and 'workqueue.c'. The nodemask created and >> updated by >> 'mem_cgroup_may_update_nodemask()' does not appear to be the same mask. > > Are you sure you're looking at 3af229f2071f? It only adds one line of code; > the reduction of node_possible_map. > The 3rd file in the patch set removes, - nodes_and(node_possible_map, node_possible_map, node_online_map); I need to add bits to 'node_possible_map' -- bits which may not be used for the memory at boot, but which would be used when memory is hot-added later. I haven't found anything outside of the boot code that adds bits to the 'possible' mask. -- Michael W. Bringmann Linux Technology Center IBM Corporation Tie-Line 363-5196 External: (512) 286-5196 Cell: (512) 466-0650 m...@linux.vnet.ibm.com