On 22/01/21 11:09, Song Bao Hua (Barry Song) wrote: >> -----Original Message----- >> From: Dietmar Eggemann [mailto:dietmar.eggem...@arm.com] >> > For example, every cpu with the below numa_distance can have >> > "groups don't span domain->span": >> > node 0 1 2 3 >> > 0: 10 12 20 22 >> > 1: 12 10 22 24 >> > 2: 20 22 10 12 >> > 3: 22 24 12 10 >> 2 20 2 >> So this should look like: 1 --- 0 ---- 2 --- 3 > > Yes. So here we are facing another problem: > kernel/sched/topology.c has an assumption that: > node_distance(0,j) includes all distances in > node_distance(i,j). > > void sched_init_numa(void) > { > ... > * > * Assumes node_distance(0,j) includes all distances in > * node_distance(i,j) in order to avoid cubic time. > */ > next_distance = curr_distance; > for (i = 0; i < nr_node_ids; i++) { > for (j = 0; j < nr_node_ids; j++) { > for (k = 0; k < nr_node_ids; k++) > } > > but obviously we are not this case. Right now, we are getting > some performance decrease due to this, probably I'll start another > thread for it. >
It's not too difficult to solve that one; I must still have a patch laying somewhere using a bitmap - this relies on the ACPI spec stating distance values are 8bit, which gives us a reasonable bound for the bitmap size. Let me fish this out. > Thanks > Barry
