From: Willy Tarreau <w@1wt.eu>
Date: Thu, 27 Feb 2025 18:50:09 +0000 (+0100)
Subject: MINOR: cpu-topo: consider capacity when forming clusters
X-Git-Tag: v3.2-dev8~52
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=204ac3c0b6b0af854de8c33a6b8b85b592f2f045;p=thirdparty%2Fhaproxy.git

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 5c3479bbb..834982222 100644
--- 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++;
 		}