On Fri, Feb 07, 2025 at 11:46:51AM -1000, Tejun Heo wrote: > On Fri, Feb 07, 2025 at 09:40:49PM +0100, Andrea Righi wrote: > > +/** > > + * for_each_numa_node - iterate over nodes at increasing distances from a > > + * given starting node. > > + * @node: the iteration variable and the starting node. > > + * @unvisited: a nodemask to keep track of the unvisited nodes. > > + * @state: state of NUMA nodes to iterate. > > + * > > + * This macro iterates over NUMA node IDs in increasing distance from the > > + * starting @node and yields MAX_NUMNODES when all the nodes have been > > + * visited. > > + * > > + * The difference between for_each_node() and for_each_numa_node() is that > > + * the former allows to iterate over nodes in numerical order, whereas the > > + * latter iterates over nodes in increasing order of distance. > > + * > > + * This complexity of this iterator is O(N^2), where N represents the > > + * number of nodes, as each iteration involves scanning all nodes to > > + * find the one with the shortest distance. > > + * > > + * Requires rcu_lock to be held. > > + */ > > +#define for_each_numa_node(node, unvisited, state) \ > > + for (int start = (node), \ > > + node = numa_nearest_nodemask((start), (state), &(unvisited)); \ > > + node < MAX_NUMNODES; \ > > + node_clear(node, (unvisited)), \ > > + node = numa_nearest_nodemask((start), (state), &(unvisited))) > > + > > /** > > * for_each_numa_hop_mask - iterate over cpumasks of increasing NUMA distance > > * from a given node. > > Bikeshedding: Maybe this has already been argued back and forth but I find > the distinction between for_each_node() and for_each_numa_node() way too > subtle. I wouldn't suspect that they are doing different things when > glancing through their usages in isolation. Can we add *something* to the > name that indicates that this is iteration by distance? The next one uses > "hop" which is fine, "_by_dist" can be fine too, or even "_from_nearest". I > don't really care which but let's make the name clearly signal what it's > doing. > > Thanks. How about for_each_node_state_by_dist()? It's essentialy a variant of for_each_node_state(), as it also accepts a state, with the only difference that node IDs are returned in increasing distance order. -Andrea
