tests: add cpu load test for high rx

This is a regression test for
#1444

Signed-off-by: Ioana Chirca <[email protected]>

Author: ioanachirca

tests/framework/microvm.py

@@ -17,6 +17,7 @@
 
 from retry import retry
 
+import host_tools.cpu_load as cpu_tools
 import host_tools.memory as mem_tools
 import host_tools.network as net_tools
 
@@ -119,6 +120,10 @@ def __init__(
         else:
             self._memory_events_queue = None
 
+        # Cpu load monitoring has to be explicitly enabled using
+        # the `enable_cpu_load_monitor` method.
+        self._cpu_load_monitor = None
+
         # External clone/exec tool, because Python can't into clone
         self.bin_cloner_path = bin_cloner_path
 
@@ -138,6 +143,11 @@ def kill(self):
             raise mem_tools.MemoryUsageExceededException(
                 self._memory_events_queue.get())
 
+        if self._cpu_load_monitor:
+            self._cpu_load_monitor.signal_stop()
+            self._cpu_load_monitor.join()
+            self._cpu_load_monitor.check_samples()
+
     @property
     def api_session(self):
         """Return the api session associated with this microVM."""
@@ -215,6 +225,20 @@ def memory_events_queue(self, queue):
         """Set the memory usage events queue."""
         self._memory_events_queue = queue
 
+    def enable_cpu_load_monitor(self, threshold):
+        """Enable the cpu load monitor."""
+        process_pid = self.jailer_clone_pid
+        # We want to monitor the emulation thread, which is currently
+        # the first one created.
+        # A possible improvement is to find it by name.
+        thread_pid = self.jailer_clone_pid
+        self._cpu_load_monitor = cpu_tools.CpuLoadMonitor(
+            process_pid,
+            thread_pid,
+            threshold
+        )
+        self._cpu_load_monitor.start()
+
     def create_jailed_resource(self, path, create_jail=False):
         """Create a hard link to some resource inside this microvm."""
         return self.jailer.jailed_path(path, create=True,

tests/host_tools/cpu_load.py

@@ -0,0 +1,126 @@
+# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+"""Utilities for measuring cpu utilisation for a process."""
+import time
+
+from subprocess import run, CalledProcessError, PIPE
+from threading import Thread
+
+# /proc/<pid>/stat output taken from
+# https://www.man7.org/linux/man-pages/man5/proc.5.html
+STAT_UTIME_IDX = 13
+STAT_STIME_IDX = 14
+STAT_STARTTIME_IDX = 21
+
+
+class CpuLoadExceededException(Exception):
+    """A custom exception containing details on excessive cpu load."""
+
+    def __init__(self, cpu_load_samples, threshold):
+        """Compose the error message containing the cpu load details."""
+        super(CpuLoadExceededException, self).__init__(
+            'Cpu load samples {} exceeded maximum threshold {}.\n'
+            .format(cpu_load_samples, threshold)
+        )
+
+
+class CpuLoadMonitor(Thread):
+    """Class to represent a cpu load monitor for a thread."""
+
+    CPU_LOAD_SAMPLES_TIMEOUT_S = 1
+
+    def __init__(
+        self,
+        process_pid,
+        thread_pid,
+        threshold
+    ):
+        """Set up monitor attributes."""
+        Thread.__init__(self)
+        self._process_pid = process_pid
+        self._thread_pid = thread_pid
+        self._cpu_load_samples = []
+        self._threshold = threshold
+        self._should_stop = False
+
+    @property
+    def process_pid(self):
+        """Get the process pid."""
+        return self._process_pid
+
+    @property
+    def thread_pid(self):
+        """Get the thread pid."""
+        return self._thread_pid
+
+    @property
+    def threshold(self):
+        """Get the cpu load threshold."""
+        return self._threshold
+
+    @property
+    def cpu_load_samples(self):
+        """Get the cpu load samples."""
+        return self._cpu_load_samples
+
+    def signal_stop(self):
+        """Signal that the thread should stop."""
+        self._should_stop = True
+
+    def run(self):
+        """Thread for monitoring cpu load of some pid.
+
+        `/proc/<process pid>/task/<thread pid>/stat` is used to compute
+        the cpu load, which is then added to the list.
+        It is up to the caller to check the queue.
+        """
+        clock_ticks_cmd = 'getconf CLK_TCK'
+        try:
+            stdout = run(
+                    clock_ticks_cmd,
+                    shell=True,
+                    check=True,
+                    stdout=PIPE
+                ).stdout.decode('utf-8')
+        except CalledProcessError:
+            return
+        try:
+            clock_ticks = int(stdout.strip("\n"))
+        except ValueError:
+            return
+
+        while not self._should_stop:
+            try:
+                with open('/proc/uptime') as uptime_file:
+                    uptime = uptime_file.readline().strip("\n").split()[0]
+
+                with open('/proc/{pid}/task/{tid}/stat'.format(
+                    pid=self.process_pid,
+                    tid=self.thread_pid)
+                ) as stat_file:
+                    stat = stat_file.readline().strip("\n").split()
+            except IOError:
+                break
+
+            try:
+                uptime = float(uptime)
+                utime = int(stat[STAT_UTIME_IDX])
+                stime = int(stat[STAT_STIME_IDX])
+                starttime = int(stat[STAT_STARTTIME_IDX])
+            except ValueError:
+                break
+
+            total_time = utime + stime
+            seconds = uptime - starttime / clock_ticks
+            cpu_load = (total_time * 100 / clock_ticks) / seconds
+
+            if cpu_load > self.threshold:
+                self.cpu_load_samples.append(cpu_load)
+
+            time.sleep(self.CPU_LOAD_SAMPLES_TIMEOUT_S)
+
+    def check_samples(self):
+        """Check that there are no samples above the threshold."""
+        if len(self.cpu_load_samples) > 0:
+            raise CpuLoadExceededException(
+                self._cpu_load_samples, self._threshold)

tests/integration_tests/functional/test_rate_limiter.py

@@ -149,6 +149,48 @@ def test_rx_rate_limiting(test_microvm_with_ssh, network_config):
     _check_rx_rate_limit_patch(test_microvm, guest_ips)
 
 
+def test_rx_rate_limiting_cpu_load(test_microvm_with_ssh, network_config):
+    """Run iperf rx with rate limiting; verify cpu load is below threshold."""
+    test_microvm = test_microvm_with_ssh
+    test_microvm.spawn()
+
+    test_microvm.basic_config()
+
+    # Enable monitor that checks if the cpu load is over the threshold.
+    # After multiple runs, the average value for the cpu load
+    # seems to be around 10%. Setting the threshold a little
+    # higher to skip false positives.
+    threshold = 20
+    test_microvm.enable_cpu_load_monitor(threshold)
+
+    # Create interface with aggressive rate limiting enabled.
+    rx_rate_limiter_no_burst = {
+        'bandwidth': {
+            'size': 65536,  # 64KBytes
+            'refill_time': 1000  # 1s
+        }
+    }
+    _tap, _host_ip, guest_ip = test_microvm.ssh_network_config(
+        network_config,
+        '1',
+        rx_rate_limiter=rx_rate_limiter_no_burst
+    )
+
+    test_microvm.start()
+
+    # Start iperf server on guest.
+    _start_iperf_on_guest(test_microvm, guest_ip)
+
+    # Run iperf client sending UDP traffic.
+    iperf_cmd = '{} {} -u -c {} -b 1000000000 -t{} -f KBytes'.format(
+        test_microvm.jailer.netns_cmd_prefix(),
+        IPERF_BINARY,
+        guest_ip,
+        IPERF_TRANSMIT_TIME * 5
+    )
+    _iperf_out = _run_local_iperf(iperf_cmd)
+
+
 def _check_tx_rate_limiting(test_microvm, guest_ips, host_ips):
     """Check that the transmit rate is within expectations."""
     # Start iperf on the host as this is the tx rate limiting test.