Re: [PATCH 1/3] sched/topology: Allow archs to populate distance map

* Valentin Schneider [off-list ref] [2021-05-25 11:21:02]:

On 24/05/21 21:48, Srikar Dronamraju wrote:

quoted

* Valentin Schneider [off-list ref] [2021-05-24 15:16:09]:

quoted

Ok so from your arch you can figure out the *size* of the set of unique
distances, but not the individual node_distance(a, b)... That's quite
unfortunate.

Yes, thats true.

quoted

I suppose one way to avoid the hook would be to write some "fake" distance
values into your distance_lookup_table[] for offline nodes using your
distance_ref_point_depth thing, i.e. ensure an iteration of
node_distance(a, b) covers all distance values [1]. You can then keep patch
3 around, and that should roughly be it.

Yes, this would suffice but to me its not very clean.
static int found[distance_ref_point_depth];

for_each_node(node){
      int i, nd, distance = LOCAL_DISTANCE;
              goto out;

      nd = node_distance(node, first_online_node)
      for (i=0; i < distance_ref_point_depth; i++, distance *= 2) {
              if (node_online) {
                      if (distance != nd)
                              continue;
                      found[i] ++;
                      break;
              }
              if (found[i])
                      continue;
              distance_lookup_table[node][i] = distance_lookup_table[first_online_node][i];
              found[i] ++;
              break;
      }
}

But do note: We are setting a precedent for node distance between two nodes
to change.

Indeed. AFAICT it's that or the unique-distance-values hook :/

Peter,

Please let me know which approach would you prefer.
I am open to try any other approach too.

In my humble opinion, unique-distance-values hook is more cleaner.
Do you still have any concerns with the unique-distance-values hook?

-- 
Thanks and Regards
Srikar Dronamraju