Remove redundant calls to get child scheduler group during initializa…

…tion

The QoS orchagent call SAI APIs to get the number of child scheduler groups
and then initialize them.
After that, the size of child scheduler groups vector will be non-zero,
which indicates the child scheduler groups have been initialized and
prevent QoS orchagent from calling SAI APIs.
However, on Mellanox platform, some scheduler groups don't have child group,
leaving size of child scheduler groups always being zero.
This causes QoS orchagent to call the SAI API each time the scheduler group
is handled, which wastes a lot of time especially during fast reboot.

An extra flag indicating whether the child groups have been initialized
is introduced to avoid the redundant calls.

Signed-off-by: Stephen Sun <stephens@nvidia.com>

orchagent/qosorch.cpp

@@ -972,18 +972,29 @@ sai_object_id_t QosOrch::getSchedulerGroup(const Port &port, const sai_object_id
 
         m_scheduler_group_port_info[port.m_port_id] = {
             .groups = std::move(groups),
-            .child_groups = std::vector<std::vector<sai_object_id_t>>(groups_count)
+            .child_groups = std::vector<std::vector<sai_object_id_t>>(groups_count),
+            .group_has_been_initialized = std::vector<bool>(groups_count)
         };
-     }
+
+        SWSS_LOG_INFO("Port %s has been initialized with %u group(s)", port.m_alias.c_str(), groups_count);
+    }
 
     /* Lookup groups to which queue belongs */
-    const auto& groups = m_scheduler_group_port_info[port.m_port_id].groups;
+    auto& scheduler_group_port_info = m_scheduler_group_port_info[port.m_port_id];
+    const auto& groups = scheduler_group_port_info.groups;
     for (uint32_t ii = 0; ii < groups.size() ; ii++)
     {
         const auto& group_id = groups[ii];
-        const auto& child_groups_per_group = m_scheduler_group_port_info[port.m_port_id].child_groups[ii];
+        const auto& child_groups_per_group = scheduler_group_port_info.child_groups[ii];
         if (child_groups_per_group.empty())
         {
+            if (scheduler_group_port_info.group_has_been_initialized[ii])
+            {
+                // skip this iteration if it has been initialized which means there're no children in this group
+                SWSS_LOG_INFO("No child group for port %s group %lx, skip", port.m_alias.c_str(), group_id);
+                continue;
+            }
+
             attr.id = SAI_SCHEDULER_GROUP_ATTR_CHILD_COUNT;//Number of queues/groups childs added to scheduler group
             sai_status = sai_scheduler_group_api->get_scheduler_group_attribute(group_id, 1, &attr);
             if (SAI_STATUS_SUCCESS != sai_status)
@@ -997,14 +1008,18 @@ sai_object_id_t QosOrch::getSchedulerGroup(const Port &port, const sai_object_id
             }
 
             uint32_t child_count = attr.value.u32;
-            vector<sai_object_id_t> child_groups(child_count);
+
+            SWSS_LOG_INFO("Port %s group %lx has been initialized with %u child group(s)", port.m_alias.c_str(), group_id, child_count);
+            scheduler_group_port_info.group_has_been_initialized[ii] = true;
 
             // skip this iteration if there're no children in this group
             if (child_count == 0)
             {
+                SWSS_LOG_INFO("No child group for port %s group %lx, skip", port.m_alias.c_str(), group_id);
                 continue;
             }
 
+            vector<sai_object_id_t> child_groups(child_count);
             attr.id = SAI_SCHEDULER_GROUP_ATTR_CHILD_LIST;
             attr.value.objlist.list = child_groups.data();
             attr.value.objlist.count = child_count;
@@ -1019,13 +1034,15 @@ sai_object_id_t QosOrch::getSchedulerGroup(const Port &port, const sai_object_id
                 }
             }
 
-            m_scheduler_group_port_info[port.m_port_id].child_groups[ii] = std::move(child_groups);
+            scheduler_group_port_info.child_groups[ii] = std::move(child_groups);
         }
 
         for (const auto& child_group_id: child_groups_per_group)
         {
+            SWSS_LOG_INFO("Check child group %lx for port %s group %lx", child_group_id, port.m_alias.c_str(), group_id);
             if (child_group_id == queue_id)
             {
+                SWSS_LOG_INFO("Found group id %lx for port %s queue %lx", group_id, port.m_alias.c_str(), queue_id);
                 return group_id;
             }
         }

orchagent/qosorch.h

@@ -162,6 +162,7 @@ class QosOrch : public Orch
     {
         std::vector<sai_object_id_t> groups;
         std::vector<std::vector<sai_object_id_t>> child_groups;
+        std::vector<bool> group_has_been_initialized;
     };
 
     std::unordered_map<sai_object_id_t, SchedulerGroupPortInfo_t> m_scheduler_group_port_info;