MINOR: cpu-topo: consider capacity when forming clusters

By using the cluster+capacity sorting function we can detect
heterogneous clusters which are not properly reported. Thanks to this,
the following misnumbered machine featuring 4 big cores, 4 medium ones
an 4 small ones is properly detected with its clusters correctly
assigned:

      [keep] thr=  0 -> cpu=  0 pk=00 no=00 cl=000 ts=000 capa=1024
      [keep] thr=  1 -> cpu=  1 pk=00 no=00 cl=002 ts=008 capa=278
      [keep] thr=  2 -> cpu=  2 pk=00 no=00 cl=002 ts=009 capa=278
      [keep] thr=  3 -> cpu=  3 pk=00 no=00 cl=002 ts=010 capa=278
      [keep] thr=  4 -> cpu=  4 pk=00 no=00 cl=002 ts=011 capa=278
      [keep] thr=  5 -> cpu=  5 pk=00 no=00 cl=001 ts=004 capa=905
      [keep] thr=  6 -> cpu=  6 pk=00 no=00 cl=001 ts=005 capa=905
      [keep] thr=  7 -> cpu=  7 pk=00 no=00 cl=001 ts=006 capa=866
      [keep] thr=  8 -> cpu=  8 pk=00 no=00 cl=001 ts=007 capa=866
      [keep] thr=  9 -> cpu=  9 pk=00 no=00 cl=000 ts=001 capa=984
      [keep] thr= 10 -> cpu= 10 pk=00 no=00 cl=000 ts=002 capa=984
      [keep] thr= 11 -> cpu= 11 pk=00 no=00 cl=000 ts=003 capa=1024

Also this has the benefit of always assigning highest performance
clusters with the smallest IDs so that simple configs can decide to
simply bind to cluster 0 or clusters 0,1 and benefit from optimal
performance.

diff --git a/src/cpu_topo.c b/src/cpu_topo.c
index 5c3479bbb5309808d022f3dc226ffb49c09a548a..8349822227bc0bb2aaf2ca18c32581b4ead49a84 100644 (file)
--- a/src/cpu_topo.c
+++ b/src/cpu_topo.c
@@ -684,10 +684,12 @@ void cpu_compose_clusters(void)
        int curr_gid, prev_gid;
        int curr_lid, prev_lid;
 
-       /* Now we'll sort CPUs by topology and assign cluster IDs to those that
-        * don't yet have one, based on the die/pkg/llc.
+       /* Now we'll sort CPUs by topology/cluster/capacity and assign cluster
+        * IDs to those that don't have one, based on the die/pkg/lcc, and
+        * double-check that capacity within a cluster doesn't vary by +/- 5%,
+        * otherwise it indicates different clusters (typically big.little).
         */
-       cpu_reorder_by_locality(ha_cpu_topo, cpu_topo_maxcpus);
+       cpu_reorder_by_cluster_capa(ha_cpu_topo, cpu_topo_maxcpus);
 
        prev_gid = prev_lid = -2; // make sure it cannot match even unassigned ones
        curr_gid = curr_lid = -1;
@@ -710,7 +712,10 @@ void cpu_compose_clusters(void)
                         (ha_cpu_topo[cpu].ca_id[4] < 0 && // no l4 ? check L3
                          ((ha_cpu_topo[cpu].ca_id[3] != ha_cpu_topo[cpu-1].ca_id[3]) ||
                           (ha_cpu_topo[cpu].ca_id[3] < 0 && // no l3 ? check L2
-                           (ha_cpu_topo[cpu].ca_id[2] != ha_cpu_topo[cpu-1].ca_id[2]))))) {
+                           (ha_cpu_topo[cpu].ca_id[2] != ha_cpu_topo[cpu-1].ca_id[2])))) ||
+                        (ha_cpu_topo[cpu].capa > 0 && ha_cpu_topo[cpu-1].capa > 0 &&
+                         (ha_cpu_topo[cpu].capa * 100 < ha_cpu_topo[cpu-1].capa * 95 ||
+                          ha_cpu_topo[cpu].capa * 95  > ha_cpu_topo[cpu-1].capa * 100))) {
                        curr_gid++;
                        curr_lid++;
                }