dragonpilot/common/realtime.py

"""Utilities for reading real time clocks and keeping soft real time constraints."""
import os
import time
import platform
import subprocess
import multiprocessing
from cffi import FFI

# Build and load cython module
import pyximport
installer = pyximport.install(inplace=True, build_dir='/tmp')
from common.clock import monotonic_time, sec_since_boot  # pylint: disable=no-name-in-module, import-error
pyximport.uninstall(*installer)
assert monotonic_time
assert sec_since_boot


# time step for each process
DT_CTRL = 0.01  # controlsd
DT_PLAN = 0.05  # mpc
DT_MDL = 0.05  # model
DT_RDR = 0.05  # radar
DT_DMON = 0.1  # driver monitoring
DT_TRML = 0.5  # thermald and manager


ffi = FFI()
ffi.cdef("long syscall(long number, ...);")
libc = ffi.dlopen(None)


def set_realtime_priority(level):
  if os.getuid() != 0:
    print("not setting priority, not root")
    return
  if platform.machine() == "x86_64":
    NR_gettid = 186
  elif platform.machine() == "aarch64":
    NR_gettid = 178
  else:
    raise NotImplementedError

  tid = libc.syscall(NR_gettid)
  return subprocess.call(['chrt', '-f', '-p', str(level), str(tid)])


class Ratekeeper():
  def __init__(self, rate, print_delay_threshold=0.):
    """Rate in Hz for ratekeeping. print_delay_threshold must be nonnegative."""
    self._interval = 1. / rate
    self._next_frame_time = sec_since_boot() + self._interval
    self._print_delay_threshold = print_delay_threshold
    self._frame = 0
    self._remaining = 0
    self._process_name = multiprocessing.current_process().name

  @property
  def frame(self):
    return self._frame

  @property
  def remaining(self):
    return self._remaining

  # Maintain loop rate by calling this at the end of each loop
  def keep_time(self):
    lagged = self.monitor_time()
    if self._remaining > 0:
      time.sleep(self._remaining)
    return lagged

  # this only monitor the cumulative lag, but does not enforce a rate
  def monitor_time(self):
    lagged = False
    remaining = self._next_frame_time - sec_since_boot()
    self._next_frame_time += self._interval
    if self._print_delay_threshold is not None and remaining < -self._print_delay_threshold:
      print("%s lagging by %.2f ms" % (self._process_name, -remaining * 1000))
      lagged = True
    self._frame += 1
    self._remaining = remaining
    return lagged