Added scheduling algorithms STFQ and WFQ

This commit adds the following two scheduling algorithms to the repo
using the new framework:
- Weighted Fair Queueing (WFQ)
- Start-Time Fair Queuing (STFQ)

Signed-off-by: Frey Alfredsson <[email protected]>

queue-exp/pifo_stfq.py

@@ -5,6 +5,15 @@
 #
 # pifo-stfq.py
 
+"""Start-Time Fair Queuing (STFQ)
+
+This scheduling algorithm is mentioned in the paper "Programmable packet
+scheduling at line rate" by Sivaraman, Anirudh, et al.
+
+It schedules packets by their start time within a flow. It defines the start
+time as the finish time of the last enqueued packet within a flow.
+"""
+
 __copyright__ = """
 Copyright (c) 2021 Toke Høiland-Jørgensen <[email protected]>
 Copyright (c) 2021 Frey Alfredsson <[email protected]>
@@ -26,23 +35,39 @@
 """
 
 from pifo_lib import Packet, Runner, Pifo
+from pifo_lib import SchedulingAlgorithm
+
 
+class Stfq(SchedulingAlgorithm):
+    """Start-Time Fair Queuing (STFQ)"""
 
-class Stfq(Pifo):
     def __init__(self):
-        super().__init__()
-        self.last_finish = {}
-        self.virt_time = 0
+        self._pifo = Pifo()
+
+        self._last_finish = {}
+        self._virt_time = 0
 
     def get_rank(self, pkt):
-        flow = pkt.flow
-        if flow in self.last_finish:
-            rank = max(self.virt_time, self.last_finish[flow])
+        flow_id = pkt.flow
+        if flow_id in self._last_finish:
+            rank = max(self._virt_time, self._last_finish[flow_id])
         else:
-            rank = self.virt_time
-        self.last_finish[flow] = rank + pkt.length
+            rank = self._virt_time
+        self._last_finish[flow_id] = rank + pkt.length
         return rank
 
+    def enqueue(self, item):
+        rank = self.get_rank(item)
+        self._pifo.enqueue(item, rank)
+
+    def dequeue(self):
+        return self._pifo.dequeue()
+
+    def dump(self):
+        self._pifo.dump()
+
+
+
 if __name__ == "__main__":
     pkts = [
         Packet(flow=1, idn=1, length=2),

queue-exp/pifo_wfq.py

@@ -0,0 +1,79 @@
+#!/usr/bin/env python3
+# coding: utf-8 -*-
+#
+# SPDX-License-Identifier: GPL-3.0-or-later
+#
+# pifo-wfq.py
+
+"""Weighted Fair Queueing (WFQ)
+
+This scheduling algorithm is mentioned in the paper "Programmable packet
+scheduling at line rate" by Sivaraman, Anirudh, et al. It schedules flows by
+giving them a fraction of the capacity using predefined weights. In our example,
+we defined flows with an odd number to get a weight of 50 and even numbers to
+get 100.
+"""
+
+__copyright__ = """
+Copyright (c) 2021 Toke Høiland-Jørgensen <[email protected]>
+Copyright (c) 2021 Frey Alfredsson <[email protected]>
+"""
+
+__license__ = """
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+
+from pifo_lib import Packet, Runner, Pifo
+from pifo_lib import SchedulingAlgorithm
+
+
+class Wfq(SchedulingAlgorithm):
+    """Weighted Fair Queueing (WFQ)"""
+
+    def __init__(self):
+        self._pifo = Pifo()
+        self._last_finish = {}
+        self._virt_time = 0
+
+    def get_rank(self, pkt):
+        flow = pkt.flow
+        weight = 50 if flow % 2 == 1 else 100
+        if flow in self._last_finish:
+            rank = max(self._virt_time, self._last_finish[flow])
+        else:
+            rank = self._virt_time
+        self._last_finish[flow] = rank + pkt.length / weight
+        return rank
+
+    def enqueue(self, item):
+        rank = self.get_rank(item)
+        self._pifo.enqueue(item, rank)
+
+    def dequeue(self):
+        return self._pifo.dequeue()
+
+    def dump(self):
+        self._pifo.dump()
+
+
+if __name__ == "__main__":
+    pkts = [
+        Packet(flow=1, idn=1, length=100),
+        Packet(flow=1, idn=2, length=100),
+        Packet(flow=1, idn=3, length=100),
+        Packet(flow=2, idn=1, length=100),
+        Packet(flow=2, idn=2, length=100),
+        Packet(flow=2, idn=3, length=100),
+    ]
+    Runner(pkts, Wfq()).run()