[libvirt] [PATCH v2 1/2] virnuma: Introduce virNumaGetDistances
The API gets a NUMA node and find distances to other nodes. The
distances are returned in an array. If an item X within the array
equals to value of zero, then there's no such node as X.
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
src/libvirt_private.syms | 1 +
src/util/virnuma.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++
src/util/virnuma.h | 3 +++
3 files changed, 59 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 4c1f61c..d73a9f5 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -1652,6 +1652,7 @@ virNodeSuspendGetTargetMask;
virDomainNumatuneMemModeTypeFromString;
virDomainNumatuneMemModeTypeToString;
virNumaGetAutoPlacementAdvice;
+virNumaGetDistances;
virNumaGetMaxNode;
virNumaGetNodeMemory;
virNumaIsAvailable;
diff --git a/src/util/virnuma.c b/src/util/virnuma.c
index 1e099eb..e8ceec8 100644
--- a/src/util/virnuma.c
+++ b/src/util/virnuma.c
@@ -217,6 +217,61 @@ virNumaGetMaxNode(void)
/**
+ * virNumaGetDistances:
+ * @node: identifier of the requested NUMA node
+ * @distances: array of distances to sibling nodes
+ * @ndistances: size of @distances
+ *
+ * Get array of distances to sibling nodes from @node. If a
+ * distances[x] equals to zero, the node x is not enabled or
+ * doesn't exist. As a special case, if @node itself refers to
+ * disabled or nonexistent NUMA node, then @distances and
+ * @ndistances are set to NULL and zero respectively.
+ *
+ * The distances are a bit of magic. For a local node the value
+ * is 10, for remote it's typically 20 meaning that time penalty
+ * for accessing a remote node is two time bigger than when
+ * accessing a local node.
+ *
+ * Returns 0 on success, -1 otherwise.
+ */
+int
+virNumaGetDistances(int node,
+ int **distances,
+ int *ndistances)
+{
+ int ret = -1;
+ int max_node;
+ size_t i;
+
+ if (!numa_bitmask_isbitset(numa_nodes_ptr, node)) {
+ VIR_DEBUG("Node %d does not exist", node);
+ *distances = NULL;
+ *ndistances = 0;
+ return 0;
+ }
+
+ if ((max_node = virNumaGetMaxNode()) < 0)
+ goto cleanup;
+
+ if (VIR_ALLOC_N(*distances, max_node) < 0)
+ goto cleanup;
+
+ *ndistances = max_node + 1;
+
+ for (i = 0; i<= max_node; i++) {
+ if (!numa_bitmask_isbitset(numa_nodes_ptr, i))
+ continue;
+
+ (*distances)[i] = numa_distance(node, i);
+ }
+
+ ret = 0;
+ cleanup:
+ return ret;
+}
+
+/**
* virNumaGetNodeMemory:
* @node: identifier of the requested NUMA node
* @memsize: returns the total size of memory in the NUMA node
diff --git a/src/util/virnuma.h b/src/util/virnuma.h
index 8464b19..fe1e966 100644
--- a/src/util/virnuma.h
+++ b/src/util/virnuma.h
@@ -58,6 +58,9 @@ int virNumaSetupMemoryPolicy(virNumaTuneDef numatune,
bool virNumaIsAvailable(void);
int virNumaGetMaxNode(void);
+int virNumaGetDistances(int node,
+ int **distances,
+ int *ndistances);
int virNumaGetNodeMemory(int node,
unsigned long long *memsize,
unsigned long long *memfree);
--
2.0.0