In order to utilize both paths on dual-ported HBAs we cannot rely
on the NUMA affinity alone, but rather have to distribute the
locality information to get the best possible result.
This patch implements a two-pass algorithm for assinging NUMA
locality information:
1. Distribute existing locality information so that no core has
more than one 'local' controller
2. Assign a 'local' controller for each of the remaining cores,
so that the overall weight (ie the sum of all locality information)
per ctrl is minimal.
Signed-off-by: Hannes Reinecke <hare@xxxxxxxx>
---
drivers/nvme/host/multipath.c | 89 ++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 88 insertions(+), 1 deletion(-)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 6d1412af7332..4944ffdf6831 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -259,15 +259,60 @@ static void nvme_requeue_work(struct work_struct *work)
}
}
+void nvme_mpath_distribute_paths(struct nvme_subsystem *subsys, int num_ctrls,
+ struct nvme_ctrl *ctrl, int numa_node)
+{
+ int node;
+ int found_node = NUMA_NO_NODE;
+ int max = LOCAL_DISTANCE * num_ctrls;
+
+ for_each_node(node) {
+ struct nvme_ctrl *c;
+ int sum = 0;
+
+ list_for_each_entry(c, &subsys->ctrls, subsys_entry)
+ sum += c->node_map[node];
+ if (sum > max) {
+ max = sum;
+ found_node = node;
+ }
+ }
+ if (found_node != NUMA_NO_NODE) {
+ ctrl->node_map[found_node] = LOCAL_DISTANCE;
+ ctrl->node_map[numa_node] = REMOTE_DISTANCE;
+ }
+}
+
+void nvme_mpath_balance_node(struct nvme_subsystem *subsys,
+ int num_ctrls, int numa_node)
+{
+ struct nvme_ctrl *found = NULL, *ctrl;
+ int max = LOCAL_DISTANCE * num_ctrls, node;
+
+ list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+ int sum = 0;
+
+ for_each_node(node)
+ sum += ctrl->node_map[node];
+ if (sum > max) {
+ max = sum;
+ found = ctrl;
+ }
+ }
+ if (found)
+ found->node_map[numa_node] = LOCAL_DISTANCE;
+}
+
void nvme_mpath_balance_subsys(struct nvme_subsystem *subsys)
{
struct nvme_ctrl *ctrl;
+ int num_ctrls = 0;
int node;
mutex_lock(&subsys->lock);
/*
- * Reset set NUMA distance
+ * 1. Reset set NUMA distance
* During creation the NUMA distance is only set
* per controller, so after connecting the other
* controllers the NUMA information on the existing
@@ -280,7 +325,49 @@ void nvme_mpath_balance_subsys(struct nvme_subsystem *subsys)
ctrl->node_map[node] =
node_distance(node, ctrl->numa_node);
}
+ num_ctrls++;
+ }
+
+ /*
+ * 2. Distribute optimal paths:
+ * Only one primary paths per node.
+ * Additional primary paths are moved to unassigned nodes.
+ */
+ for_each_node(node) {
+ bool optimal = false;
+
+ list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+ if (ctrl->node_map[node] == LOCAL_DISTANCE) {
+ if (!optimal) {
+ optimal = true;
+ continue;
+ }
+ nvme_mpath_distribute_paths(subsys, num_ctrls,
+ ctrl, node);
+ }
+ }
+ }
+
+ /*
+ * 3. Balance unassigned nodes:
+ * Each unassigned node should have one primary path;
+ * the primary path is assigned to the ctrl with the
+ * minimal weight (ie the sum of distances over all nodes)
+ */
+ for_each_node(node) {
+ bool optimal = false;
+
+ list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+ if (ctrl->node_map[node] == LOCAL_DISTANCE) {
+ optimal = true;
+ break;
+ }
+ }
+ if (optimal)
+ continue;
+ nvme_mpath_balance_node(subsys, num_ctrls, node);
}
+
mutex_unlock(&subsys->lock);
}
--
2.16.4
