Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> writes: > Hi Ying, > > On 2023/10/20 15:05, Huang, Ying wrote: >> Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> writes: >> >>> In offline_pages(), if a node becomes memoryless, we >>> will clear its N_MEMORY state by calling node_states_clear_node(). >>> But we do this after rebuilding the zonelists by calling >>> build_all_zonelists(), which will cause this memoryless node to >>> still be in the fallback list of other nodes. >> For fallback list, do you mean pgdat->node_zonelists[]? If so, in >> build_all_zonelists >> __build_all_zonelists >> build_zonelists >> build_zonelists_in_node_order >> build_zonerefs_node >> populated_zone() will be checked before adding zone into zonelist. >> So, IIUC, we will not try to allocate from the memory less node. > > Normally yes, but if it is the weird topology mentioned in [1], it's > possible to allocate memory from it, it is a memoryless node, but it > also has memory. > > In addition to the above case, I think it's reasonable to remove > memory less node from node_order[] in advance. In this way it will > not to be traversed in build_zonelists_in_node_order(). > > [1]. https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@xxxxxxxxxxxxx/ Got it! Thank you for information. I think that it may be good to include this in the patch description to avoid potential confusing in the future. -- Best Regards, Huang, Ying > Thanks, > Qi > > >> -- >> Best Regards, >> Huang, Ying >> >>> This will incur >>> some runtime overhead. >>> >>> To drop memoryless node from fallback lists in this case, just >>> call node_states_clear_node() before calling build_all_zonelists(). >>> >>> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> >>> Acked-by: David Hildenbrand <david@xxxxxxxxxx> >> [snip] >> -- >> Best Regards, >> Huang, Ying
