[Dynamic buffer calc] Bug fix: Remove PGs from an administratively do…

…wn port. (sonic-net#1652)

Remove PGs from an administratively down port.
- Introduce a new state: PORT_ADMIN_DOWN which represents the port is administratively down.
- Remove all PGs when the port is shut down and re-add all configured PGs when port is started up
- Only record the new value but don't touch BUFFER_PG_TABLE if the following events come when a port is administratively down, a port's MTU, speed, or cable length is updated, a new PG is added to a port or an existing PG is removed from a port
- Optimize the port event handling flow since refreshPriorityGroupsForPort should be called only once in case more than one fields are updated
- Optimize the Lua plugin which calculates the buffer pool size according

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

How I verified it
Run regression and vs test

cfgmgr/buffer_pool_mellanox.lua

@@ -12,7 +12,7 @@ local lossypg_400g = 0
 local result = {}
 local profiles = {}
 
-local count_up_port = 0
+local total_port = 0
 
 local mgmt_pool_size = 256 * 1024
 local egress_mirror_headroom = 10 * 1024
@@ -30,56 +30,46 @@ end
 
 local function iterate_all_items(all_items)
     table.sort(all_items)
-    local prev_port = "None"
     local port
-    local is_up
     local fvpairs
-    local status
-    local admin_down_ports = 0
     for i = 1, #all_items, 1 do
-        -- Check whether the port on which pg or tc hosts is admin down
+        -- Count the number of priorities or queues in each BUFFER_PG or BUFFER_QUEUE item
+        -- For example, there are:
+        --     3 queues in 'BUFFER_QUEUE_TABLE:Ethernet0:0-2'
+        --     2 priorities in 'BUFFER_PG_TABLE:Ethernet0:3-4'
         port = string.match(all_items[i], "Ethernet%d+")
         if port ~= nil then
-            if prev_port ~= port then
-                status = redis.call('HGET', 'PORT_TABLE:'..port, 'admin_status')
-                prev_port = port
-                if status == "down" then
-                    is_up = false
-                else
-                    is_up = true
-                end
+            local range = string.match(all_items[i], "Ethernet%d+:([^%s]+)$")
+            local profile = redis.call('HGET', all_items[i], 'profile')
+            local index = find_profile(profile)
+            if index == 0 then
+                -- Indicate an error in case the referenced profile hasn't been inserted or has been removed
+                -- It's possible when the orchagent is busy
+                -- The buffermgrd will take care of it and retry later
+                return 1
             end
-            if is_up == true then
-                local range = string.match(all_items[i], "Ethernet%d+:([^%s]+)$")
-                local profile = redis.call('HGET', all_items[i], 'profile')
-                local index = find_profile(profile)
-                local size
-                if string.len(range) == 1 then
-                    size = 1
-                else
-                    size = 1 + tonumber(string.sub(range, -1)) - tonumber(string.sub(range, 1, 1))
-                end
-                profiles[index][2] = profiles[index][2] + size
-                local speed = redis.call('HGET', 'PORT_TABLE:'..port, 'speed')
-                if speed == '400000' and profile == '[BUFFER_PROFILE_TABLE:ingress_lossy_profile]' then
-                    lossypg_400g = lossypg_400g + size
-                end
+            local size
+            if string.len(range) == 1 then
+                size = 1
+            else
+                size = 1 + tonumber(string.sub(range, -1)) - tonumber(string.sub(range, 1, 1))
+            end
+            profiles[index][2] = profiles[index][2] + size
+            local speed = redis.call('HGET', 'PORT_TABLE:'..port, 'speed')
+            if speed == '400000' and profile == '[BUFFER_PROFILE_TABLE:ingress_lossy_profile]' then
+                lossypg_400g = lossypg_400g + size
             end
         end
     end
+    return 0
 end
 
 -- Connect to CONFIG_DB
 redis.call('SELECT', config_db)
 
 local ports_table = redis.call('KEYS', 'PORT|*')
 
-for i = 1, #ports_table do
-    local status = redis.call('HGET', ports_table[i], 'admin_status')
-    if status == "up" then
-        count_up_port = count_up_port + 1
-    end
-end
+total_port = #ports_table
 
 local egress_lossless_pool_size = redis.call('HGET', 'BUFFER_POOL|egress_lossless_pool', 'size')
 
@@ -114,8 +104,12 @@ end
 local all_pgs = redis.call('KEYS', 'BUFFER_PG*')
 local all_tcs = redis.call('KEYS', 'BUFFER_QUEUE*')
 
-iterate_all_items(all_pgs)
-iterate_all_items(all_tcs)
+local fail_count = 0
+fail_count = fail_count + iterate_all_items(all_pgs)
+fail_count = fail_count + iterate_all_items(all_tcs)
+if fail_count > 0 then
+    return {}
+end
 
 local statistics = {}
 
@@ -130,7 +124,7 @@ for i = 1, #profiles, 1 do
                 size = size + lossypg_reserved
             end
             if profiles[i][1] == "BUFFER_PROFILE_TABLE:egress_lossy_profile" then
-                profiles[i][2] = count_up_port
+                profiles[i][2] = total_port
             end
             if size ~= 0 then
                 if shp_enabled and shp_size == 0 then
@@ -152,7 +146,7 @@ local lossypg_extra_for_400g = (lossypg_reserved_400g - lossypg_reserved) * loss
 accumulative_occupied_buffer = accumulative_occupied_buffer + lossypg_extra_for_400g
 
 -- Accumulate sizes for egress mirror and management pool
-local accumulative_egress_mirror_overhead = count_up_port * egress_mirror_headroom
+local accumulative_egress_mirror_overhead = total_port * egress_mirror_headroom
 accumulative_occupied_buffer = accumulative_occupied_buffer + accumulative_egress_mirror_overhead + mgmt_pool_size
 
 -- Fetch mmu_size
@@ -240,5 +234,6 @@ table.insert(result, "debug:egress_mirror:" .. accumulative_egress_mirror_overhe
 table.insert(result, "debug:shp_enabled:" .. tostring(shp_enabled))
 table.insert(result, "debug:shp_size:" .. shp_size)
 table.insert(result, "debug:accumulative xoff:" .. accumulative_xoff)
+table.insert(result, "debug:total port:" .. total_port)
 
 return result