--- /dev/null
+============================
+NUMA resource associativity
+=============================
+
+Associativity represents the groupings of the various platform resources into
+domains of substantially similar mean performance relative to resources outside
+of that domain. Resources subsets of a given domain that exhibit better
+performance relative to each other than relative to other resources subsets
+are represented as being members of a sub-grouping domain. This performance
+characteristic is presented in terms of NUMA node distance within the Linux kernel.
+From the platform view, these groups are also referred to as domains.
+
+PAPR interface currently supports different ways of communicating these resource
+grouping details to the OS. These are referred to as Form 0, Form 1 and Form2
+associativity grouping. Form 0 is the oldest format and is now considered deprecated.
+
+Hypervisor indicates the type/form of associativity used via "ibm,architecture-vec-5 property".
+Bit 0 of byte 5 in the "ibm,architecture-vec-5" property indicates usage of Form 0 or Form 1.
+A value of 1 indicates the usage of Form 1 associativity. For Form 2 associativity
+bit 2 of byte 5 in the "ibm,architecture-vec-5" property is used.
+
+Form 0
+-----
+Form 0 associativity supports only two NUMA distances (LOCAL and REMOTE).
+
+Form 1
+-----
+With Form 1 a combination of ibm,associativity-reference-points, and ibm,associativity
+device tree properties are used to determine the NUMA distance between resource groups/domains.
+
+The “ibm,associativity” property contains a list of one or more numbers (domainID)
+representing the resource’s platform grouping domains.
+
+The “ibm,associativity-reference-points” property contains a list of one or more numbers
+(domainID index) that represents the 1 based ordinal in the associativity lists.
+The list of domainID indexes represents an increasing hierarchy of resource grouping.
+
+ex:
+{ primary domainID index, secondary domainID index, tertiary domainID index.. }
+
+Linux kernel uses the domainID at the primary domainID index as the NUMA node id.
+Linux kernel computes NUMA distance between two domains by recursively comparing
+if they belong to the same higher-level domains. For mismatch at every higher
+level of the resource group, the kernel doubles the NUMA distance between the
+comparing domains.
+
+Form 2
+-------
+Form 2 associativity format adds separate device tree properties representing NUMA node distance
+thereby making the node distance computation flexible. Form 2 also allows flexible primary
+domain numbering. With numa distance computation now detached from the index value in
+"ibm,associativity-reference-points" property, Form 2 allows a large number of primary domain
+ids at the same domainID index representing resource groups of different performance/latency
+characteristics.
+
+Hypervisor indicates the usage of FORM2 associativity using bit 2 of byte 5 in the
+"ibm,architecture-vec-5" property.
+
+"ibm,numa-lookup-index-table" property contains a list of one or more numbers representing
+the domainIDs present in the system. The offset of the domainID in this property is
+used as an index while computing numa distance information via "ibm,numa-distance-table".
+
+prop-encoded-array: The number N of the domainIDs encoded as with encode-int, followed by
+N domainID encoded as with encode-int
+
+For ex:
+"ibm,numa-lookup-index-table" = {4, 0, 8, 250, 252}. The offset of domainID 8 (2) is used when
+computing the distance of domain 8 from other domains present in the system. For the rest of
+this document, this offset will be referred to as domain distance offset.
+
+"ibm,numa-distance-table" property contains a list of one or more numbers representing the NUMA
+distance between resource groups/domains present in the system.
+
+prop-encoded-array: The number N of the distance values encoded as with encode-int, followed by
+N distance values encoded as with encode-bytes. The max distance value we could encode is 255.
+The number N must be equal to the square of m where m is the number of domainIDs in the
+numa-lookup-index-table.
+
+For ex:
+ibm,numa-lookup-index-table = <3 0 8 40>;
+ibm,numa-distace-table = <9>, /bits/ 8 < 10 20 80
+ 20 10 160
+ 80 160 10>;
+ | 0 8 40
+--|------------
+ |
+0 | 10 20 80
+ |
+8 | 20 10 160
+ |
+40| 80 160 10
+
+A possible "ibm,associativity" property for resources in node 0, 8 and 40
+
+{ 3, 6, 7, 0 }
+{ 3, 6, 9, 8 }
+{ 3, 6, 7, 40}
+
+With "ibm,associativity-reference-points" { 0x3 }
+
+"ibm,lookup-index-table" helps in having a compact representation of distance matrix.
+Since domainID can be sparse, the matrix of distances can also be effectively sparse.
+With "ibm,lookup-index-table" we can achieve a compact representation of
+distance information.
#define FORM0_AFFINITY 0
#define FORM1_AFFINITY 1
+#define FORM2_AFFINITY 2
static int affinity_form;
#define MAX_DISTANCE_REF_POINTS 4
static int distance_ref_points_depth;
static const __be32 *distance_ref_points;
static int distance_lookup_table[MAX_NUMNODES][MAX_DISTANCE_REF_POINTS];
+static int numa_distance_table[MAX_NUMNODES][MAX_NUMNODES] = {
+ [0 ... MAX_NUMNODES - 1] = { [0 ... MAX_NUMNODES - 1] = -1 }
+};
+static int numa_id_index_table[MAX_NUMNODES] = { [0 ... MAX_NUMNODES - 1] = NUMA_NO_NODE };
/*
* Allocate node_to_cpumask_map based on number of available nodes
}
#endif /* CONFIG_HOTPLUG_CPU || CONFIG_PPC_SPLPAR */
+static int __associativity_to_nid(const __be32 *associativity,
+ int max_array_sz)
+{
+ int nid;
+ /*
+ * primary_domain_index is 1 based array index.
+ */
+ int index = primary_domain_index - 1;
+
+ if (!numa_enabled || index >= max_array_sz)
+ return NUMA_NO_NODE;
+
+ nid = of_read_number(&associativity[index], 1);
+
+ /* POWER4 LPAR uses 0xffff as invalid node */
+ if (nid == 0xffff || nid >= nr_node_ids)
+ nid = NUMA_NO_NODE;
+ return nid;
+}
+/*
+ * Returns nid in the range [0..nr_node_ids], or -1 if no useful NUMA
+ * info is found.
+ */
+static int associativity_to_nid(const __be32 *associativity)
+{
+ int array_sz = of_read_number(associativity, 1);
+
+ /* Skip the first element in the associativity array */
+ return __associativity_to_nid((associativity + 1), array_sz);
+}
+
+static int __cpu_form2_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
+{
+ int dist;
+ int node1, node2;
+
+ node1 = associativity_to_nid(cpu1_assoc);
+ node2 = associativity_to_nid(cpu2_assoc);
+
+ dist = numa_distance_table[node1][node2];
+ if (dist <= LOCAL_DISTANCE)
+ return 0;
+ else if (dist <= REMOTE_DISTANCE)
+ return 1;
+ else
+ return 2;
+}
+
static int __cpu_form1_relative_distance(__be32 *cpu1_assoc, __be32 *cpu2_assoc)
{
int dist = 0;
{
/* We should not get called with FORM0 */
VM_WARN_ON(affinity_form == FORM0_AFFINITY);
-
- return __cpu_form1_relative_distance(cpu1_assoc, cpu2_assoc);
+ if (affinity_form == FORM1_AFFINITY)
+ return __cpu_form1_relative_distance(cpu1_assoc, cpu2_assoc);
+ return __cpu_form2_relative_distance(cpu1_assoc, cpu2_assoc);
}
/* must hold reference to node during call */
int i;
int distance = LOCAL_DISTANCE;
- if (affinity_form == FORM0_AFFINITY)
+ if (affinity_form == FORM2_AFFINITY)
+ return numa_distance_table[a][b];
+ else if (affinity_form == FORM0_AFFINITY)
return ((a == b) ? LOCAL_DISTANCE : REMOTE_DISTANCE);
for (i = 0; i < distance_ref_points_depth; i++) {
}
EXPORT_SYMBOL(__node_distance);
-static int __associativity_to_nid(const __be32 *associativity,
- int max_array_sz)
-{
- int nid;
- /*
- * primary_domain_index is 1 based array index.
- */
- int index = primary_domain_index - 1;
-
- if (!numa_enabled || index >= max_array_sz)
- return NUMA_NO_NODE;
-
- nid = of_read_number(&associativity[index], 1);
-
- /* POWER4 LPAR uses 0xffff as invalid node */
- if (nid == 0xffff || nid >= nr_node_ids)
- nid = NUMA_NO_NODE;
- return nid;
-}
-/*
- * Returns nid in the range [0..nr_node_ids], or -1 if no useful NUMA
- * info is found.
- */
-static int associativity_to_nid(const __be32 *associativity)
-{
- int array_sz = of_read_number(associativity, 1);
-
- /* Skip the first element in the associativity array */
- return __associativity_to_nid((associativity + 1), array_sz);
-}
-
/* Returns the nid associated with the given device tree node,
* or -1 if not found.
*/
*/
void update_numa_distance(struct device_node *node)
{
+ int nid;
+
if (affinity_form == FORM0_AFFINITY)
return;
else if (affinity_form == FORM1_AFFINITY) {
initialize_form1_numa_distance(associativity);
return;
}
+
+ /* FORM2 affinity */
+ nid = of_node_to_nid_single(node);
+ if (nid == NUMA_NO_NODE)
+ return;
+
+ /*
+ * With FORM2 we expect NUMA distance of all possible NUMA
+ * nodes to be provided during boot.
+ */
+ WARN(numa_distance_table[nid][nid] == -1,
+ "NUMA distance details for node %d not provided\n", nid);
+}
+
+/*
+ * ibm,numa-lookup-index-table= {N, domainid1, domainid2, ..... domainidN}
+ * ibm,numa-distance-table = { N, 1, 2, 4, 5, 1, 6, .... N elements}
+ */
+static void initialize_form2_numa_distance_lookup_table(void)
+{
+ int i, j;
+ struct device_node *root;
+ const __u8 *numa_dist_table;
+ const __be32 *numa_lookup_index;
+ int numa_dist_table_length;
+ int max_numa_index, distance_index;
+
+ if (firmware_has_feature(FW_FEATURE_OPAL))
+ root = of_find_node_by_path("/ibm,opal");
+ else
+ root = of_find_node_by_path("/rtas");
+ if (!root)
+ root = of_find_node_by_path("/");
+
+ numa_lookup_index = of_get_property(root, "ibm,numa-lookup-index-table", NULL);
+ max_numa_index = of_read_number(&numa_lookup_index[0], 1);
+
+ /* first element of the array is the size and is encode-int */
+ numa_dist_table = of_get_property(root, "ibm,numa-distance-table", NULL);
+ numa_dist_table_length = of_read_number((const __be32 *)&numa_dist_table[0], 1);
+ /* Skip the size which is encoded int */
+ numa_dist_table += sizeof(__be32);
+
+ pr_debug("numa_dist_table_len = %d, numa_dist_indexes_len = %d\n",
+ numa_dist_table_length, max_numa_index);
+
+ for (i = 0; i < max_numa_index; i++)
+ /* +1 skip the max_numa_index in the property */
+ numa_id_index_table[i] = of_read_number(&numa_lookup_index[i + 1], 1);
+
+
+ if (numa_dist_table_length != max_numa_index * max_numa_index) {
+ WARN(1, "Wrong NUMA distance information\n");
+ /* consider everybody else just remote. */
+ for (i = 0; i < max_numa_index; i++) {
+ for (j = 0; j < max_numa_index; j++) {
+ int nodeA = numa_id_index_table[i];
+ int nodeB = numa_id_index_table[j];
+
+ if (nodeA == nodeB)
+ numa_distance_table[nodeA][nodeB] = LOCAL_DISTANCE;
+ else
+ numa_distance_table[nodeA][nodeB] = REMOTE_DISTANCE;
+ }
+ }
+ }
+
+ distance_index = 0;
+ for (i = 0; i < max_numa_index; i++) {
+ for (j = 0; j < max_numa_index; j++) {
+ int nodeA = numa_id_index_table[i];
+ int nodeB = numa_id_index_table[j];
+
+ numa_distance_table[nodeA][nodeB] = numa_dist_table[distance_index++];
+ pr_debug("dist[%d][%d]=%d ", nodeA, nodeB, numa_distance_table[nodeA][nodeB]);
+ }
+ }
+ of_node_put(root);
}
static int __init find_primary_domain_index(void)
*/
if (firmware_has_feature(FW_FEATURE_OPAL)) {
affinity_form = FORM1_AFFINITY;
+ } else if (firmware_has_feature(FW_FEATURE_FORM2_AFFINITY)) {
+ dbg("Using form 2 affinity\n");
+ affinity_form = FORM2_AFFINITY;
} else if (firmware_has_feature(FW_FEATURE_FORM1_AFFINITY)) {
dbg("Using form 1 affinity\n");
affinity_form = FORM1_AFFINITY;
index = of_read_number(&distance_ref_points[1], 1);
} else {
+ /*
+ * Both FORM1 and FORM2 affinity find the primary domain details
+ * at the same offset.
+ */
index = of_read_number(distance_ref_points, 1);
}
-
/*
* Warn and cap if the hardware supports more than
* MAX_DISTANCE_REF_POINTS domains.
dbg("NUMA associativity depth for CPU/Memory: %d\n", primary_domain_index);
+ /*
+ * If it is FORM2 initialize the distance table here.
+ */
+ if (affinity_form == FORM2_AFFINITY)
+ initialize_form2_numa_distance_lookup_table();
+
/*
* Even though we connect cpus to numa domains later in SMP
* init, we need to know the node ids now. This is because
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