snabb top: refactor queue stats filtering

Use a simpler method to figure out which queue stats to filter
out. Revert change to symlink each counter for intel_mp and
just symlink the whole folder again. Then add a counter in the
per-app shm that just stores the rxcounter/txcounter.

Snabb top then looks through all the apps in a process and filters
out queue counters that don't match any app. This is not totally precise
in the case that a process uses multiple NICs with counters set
(it may show more counters than necessary).

src/apps/intel_mp/intel_mp.lua

@@ -313,15 +313,6 @@ byPciID = {
   [0x10fb] = { registers = "82599ES", driver = Intel82599, max_q = 16 }
 }
 
--- constant used in constructor below, keep synced with the actual
--- keys used for the driver stats shm frame that should be shared between
--- NIC processes
-local shm_frame_keys = { "dtime", "mtu", "speed", "status", "type",
-                         "promisc", "macaddr", "rxbytes", "rxpackets",
-                         "rxmcast", "rxbcast", "rxdrop", "rxerrors",
-                         "txbytes", "txpackets", "txmcast", "txbcast",
-                         "txdrop", "txerrors", "rxdmapackets" }
-
 -- The `driver' variable is used as a reference to the driver class in
 -- order to interchangeably use NIC drivers.
 driver = Intel
@@ -388,8 +379,10 @@ function Intel:new (conf)
 
    -- Initialize per app statistics
    self.shm = {
-      mtu    = {counter, self.mtu},
-      txdrop = {counter}
+      mtu       = {counter, self.mtu},
+      rxcounter = {counter, self.rxcounter},
+      txcounter = {counter, self.txcounter},
+      txdrop    = {counter}
    }
 
    -- Figure out if we are supposed to collect device statistics
@@ -424,33 +417,14 @@ function Intel:new (conf)
       self:init_queue_stats(frame)
       self.stats = shm.create_frame(self.shm_root.."stats", frame)
       self.sync_timer = lib.throttle(0.01)
-   else
-      -- use a dummy frame, this is just used to populate shm_frame_keys
-      self:init_queue_stats({})
-   end
-
-   -- Alias each counter in the shared stats frame in each process's pci dir
-   -- Not all counters in pci/ are shared, some are process specific
-   for _, name in ipairs(shm_frame_keys) do
-      -- The conditional checks if the symlink exists with lstat since
-      -- shm.exists requires the target exist, and the run_stats process
-      -- could go down and make the target cease to exist
-      if not S.lstat(shm.root.."/"..S.getpid().."/pci/"..
-                     self.pciaddress.."/"..name..".counter") then
-         shm.alias("pci/"..self.pciaddress.."/"..name..".counter",
-                   self.shm_root.."stats".."/"..name..".counter")
-      end
    end
 
-   -- Expose per-instance queue counter assignment, which allows a program like
-   -- `snabb top` to associate PIDs to queue counters
-   if self.rxcounter then
-      local rxcs = counter.create("pci/"..self.pciaddress.."/rxcounters.counter")
-      counter.set(rxcs, lib.bits({rxc=self.rxcounter}, counter.read(rxcs)))
-   end
-   if self.txcounter then
-      local txcs = counter.create("pci/"..self.pciaddress.."/txcounters.counter")
-      counter.set(txcs, lib.bits({rxc=self.txcounter}, counter.read(txcs)))
+   -- Alias to the shared stats frame in each process's pci dir
+   -- The conditional checks if the symlink exists with lstat since
+   -- shm.exists requires the target exist, and the run_stats process
+   -- could go down and make the target cease to exist
+   if not S.lstat(shm.root.."/"..S.getpid().."/pci/"..self.pciaddress) then
+      shm.alias("pci/"..self.pciaddress, self.shm_root.."stats")
    end
 
    alarms.add_to_inventory(
@@ -1219,7 +1193,6 @@ function Intel1g:init_queue_stats (frame)
          local name = "q" .. i .. "_" .. k
          table.insert(self.queue_stats, name)
          table.insert(self.queue_stats, self.r[v][i])
-         table.insert(shm_frame_keys, name)
          frame[name] = {counter}
       end
    end
@@ -1327,7 +1300,6 @@ function Intel82599:init_queue_stats (frame)
          local name = "q" .. i .. "_" .. k
          table.insert(self.queue_stats, name)
          table.insert(self.queue_stats, self.r[v][i])
-         table.insert(shm_frame_keys, name)
          frame[name] = {counter}
       end
    end

src/program/top/top.lua

@@ -352,14 +352,32 @@ local function compute_histograms_tree(histograms)
    return ret
 end
 
--- given a prefix (tx or rx), bitmap of enabled queue counters, & a table
--- of counters, remove the counters not matching the bitmap
-local function filter_queue_counters(prefix, bitmap, counters)
-   for i=0, 15 do
-      if not lib.bitset(bitmap, i) then
-         counters["q"..i.."_"..prefix.."packets"] = nil
-         counters["q"..i.."_"..prefix.."drops"] = nil
-         counters["q"..i.."_"..prefix.."bytes"] = nil
+-- given a table of apps in the process & table of sets of pci counters,
+-- remove the counters not used by the apps in the process
+local function filter_queue_counters(apps, pcis)
+   local enabled_rx = 0
+   local enabled_tx = 0
+   for _, app in pairs(apps) do
+      for name, leaf in pairs(app) do
+         if name == "rxcounter" then
+            enabled_rx = lib.bits({bit=leaf.value()}, enabled_rx)
+         elseif name == "txcounter" then
+            enabled_tx = lib.bits({bit=leaf.value()}, enabled_tx)
+         end
+      end
+   end
+   for _, pci in pairs(pcis) do
+      for i=0, 15 do
+         if not lib.bitset(enabled_rx, i) then
+            pci["q"..i.."_".."rxpackets"] = nil
+            pci["q"..i.."_".."rxdrops"] = nil
+            pci["q"..i.."_".."rxbytes"] = nil
+         end
+         if not lib.bitset(enabled_tx, i) then
+            pci["q"..i.."_".."txpackets"] = nil
+            pci["q"..i.."_".."txdrops"] = nil
+            pci["q"..i.."_".."txbytes"] = nil
+         end
       end
    end
 end
@@ -379,15 +397,8 @@ local function compute_counters_tree(counters, rrds)
             function() return counter.read(v) end, rrds[k])
       end
    end
-   if ret.pci then
-      for pci, counters in pairs(ret.pci) do
-         if counters.rxcounters then
-            filter_queue_counters("rx", counters.rxcounters.value(), counters)
-         end
-         if counters.txcounters then
-            filter_queue_counters("tx", counters.txcounters.value(), counters)
-         end
-      end
+   if ret.pci and ret.apps then
+      filter_queue_counters(ret.apps, ret.pci)
    end
    -- The rxpackets and rxbytes link counters are redundant.
    if ret.links then