Messages in this thread | | | Date | Tue, 23 May 2017 16:49:22 -0500 | From | Reza Arbab <> | Subject | Re: [Patch 2/2]: powerpc/hotplug/mm: Fix hot-add memory node assoc |
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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.
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.
-- Reza Arbab
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