memattrs: only build memory tiers and set subtypes when not loading from XML

XML already has its own subtype and tiers.
If importing from <2.8 (no subtypes) or <2.10 (no tiers), one may set
HWLOC_MEMTIERS_REFRESH=1 to force refresh them.
May also be used if the backend set wrong subtypes for some reason.

Signed-off-by: Brice Goglin <[email protected]>

Author: bgoglin

doc/hwloc.doxy

@@ -1136,6 +1136,12 @@ following environment variables.
   If an empty value or <tt>none</tt> is given, tiers are entirely disabled.
   </dd>
 
+<dt>HWLOC_MEMTIERS_REFRESH=1</dt>
+  <dd>Force the rebuilding of memory tiers.
+  This is mostly useful when importing a XML topology from an old hwloc
+  version which was not able to guess memory subtypes and tiers.
+  </dd>
+
 <dt>HWLOC_GROUPING=1</dt>
   <dd>enables or disables objects grouping based on distances.
   By default, hwloc uses distance matrices between objects (either read

hwloc/memattrs.c

@@ -1425,6 +1425,7 @@ hwloc__group_memory_tiers(hwloc_topology_t topology,
   /* Sort nodes.
    * We could also sort by the existing subtype.
    * KNL is the only case where subtypes are set in backends, but we set memattrs as well there.
+   * Also HWLOC_MEMTIERS_REFRESH would be a special value to ignore existing subtypes.
    */
   hwloc_debug("Sorting memory node infos...\n");
   qsort(nodeinfos, n, sizeof(*nodeinfos), compare_node_infos_by_type_and_bw);
@@ -1809,12 +1810,11 @@ hwloc__apply_memory_tiers_subtypes(hwloc_topology_t topology,
 }
 
 int
-hwloc_internal_memattrs_guess_memory_tiers(hwloc_topology_t topology)
+hwloc_internal_memattrs_guess_memory_tiers(hwloc_topology_t topology, int force_subtype)
 {
   struct hwloc_memory_tier_s *tiers;
   unsigned nr_tiers;
   unsigned i;
-  int force_subtype = 0;
   const char *env;
 
   env = getenv("HWLOC_MEMTIERS");

hwloc/topology.c

@@ -4299,10 +4299,13 @@ hwloc_topology_load (struct hwloc_topology *topology)
   }
 
   if (!(topology->flags & HWLOC_TOPOLOGY_FLAG_NO_MEMATTRS)) {
+    int force_memtiers = (getenv("HWLOC_MEMTIERS_REFRESH") != NULL);
     /* Same for memattrs */
     hwloc_internal_memattrs_need_refresh(topology);
     hwloc_internal_memattrs_refresh(topology);
-    hwloc_internal_memattrs_guess_memory_tiers(topology);
+    /* update memtiers unless XML */
+    if (force_memtiers || strcmp(topology->backends->component->name, "xml"))
+      hwloc_internal_memattrs_guess_memory_tiers(topology, force_memtiers);
   }
 
   topology->state &= ~HWLOC_TOPOLOGY_STATE_IS_LOADING;

include/private/private.h

@@ -431,7 +431,7 @@ extern void hwloc_internal_memattrs_need_refresh(hwloc_topology_t topology);
 extern void hwloc_internal_memattrs_refresh(hwloc_topology_t topology);
 extern int hwloc_internal_memattrs_dup(hwloc_topology_t new, hwloc_topology_t old);
 extern int hwloc_internal_memattr_set_value(hwloc_topology_t topology, hwloc_memattr_id_t id, hwloc_obj_type_t target_type, hwloc_uint64_t target_gp_index, unsigned target_os_index, struct hwloc_internal_location_s *initiator, hwloc_uint64_t value);
-extern int hwloc_internal_memattrs_guess_memory_tiers(hwloc_topology_t topology);
+extern int hwloc_internal_memattrs_guess_memory_tiers(hwloc_topology_t topology, int force_subtype);
 
 extern void hwloc_internal_cpukinds_init(hwloc_topology_t topology);
 extern int hwloc_internal_cpukinds_rank(hwloc_topology_t topology);

tests/hwloc/memtiers.c

@@ -137,6 +137,8 @@ main(void)
 
   hwloc_topology_export_xmlbuffer(topology, &xmlbuffer, &buflen, 0);
 
+  putenv((char*)"HWLOC_MEMTIERS_REFRESH=1");
+
   printf("checking NVM and SPM subtypes are set on XML reload\n");
   printf("UNKNOWN should be before SPM and NVM in tiers since we have no BW\n");
   err = hwloc_topology_init(&new);