You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
94 lines
2.5 KiB
94 lines
2.5 KiB
"""Utilities for reading real time clocks and keeping soft real time constraints."""
|
|
import time
|
|
import ctypes
|
|
import platform
|
|
import subprocess
|
|
import multiprocessing
|
|
import os
|
|
|
|
CLOCK_MONOTONIC_RAW = 4 # see <linux/time.h>
|
|
CLOCK_BOOTTIME = 7
|
|
|
|
class timespec(ctypes.Structure):
|
|
_fields_ = [
|
|
('tv_sec', ctypes.c_long),
|
|
('tv_nsec', ctypes.c_long),
|
|
]
|
|
|
|
|
|
try:
|
|
libc = ctypes.CDLL('libc.so', use_errno=True)
|
|
except OSError:
|
|
try:
|
|
libc = ctypes.CDLL('libc.so.6', use_errno=True)
|
|
except OSError:
|
|
libc = None
|
|
|
|
if libc is not None:
|
|
libc.clock_gettime.argtypes = [ctypes.c_int, ctypes.POINTER(timespec)]
|
|
|
|
def clock_gettime(clk_id):
|
|
if platform.system() == "darwin":
|
|
# TODO: fix this
|
|
return time.time()
|
|
else:
|
|
t = timespec()
|
|
if libc.clock_gettime(clk_id, ctypes.pointer(t)) != 0:
|
|
errno_ = ctypes.get_errno()
|
|
raise OSError(errno_, os.strerror(errno_))
|
|
return t.tv_sec + t.tv_nsec * 1e-9
|
|
|
|
def monotonic_time():
|
|
return clock_gettime(CLOCK_MONOTONIC_RAW)
|
|
|
|
def sec_since_boot():
|
|
return clock_gettime(CLOCK_BOOTTIME)
|
|
|
|
|
|
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(object):
|
|
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):
|
|
self.monitor_time()
|
|
if self._remaining > 0:
|
|
time.sleep(self._remaining)
|
|
|
|
# this only monitor the cumulative lag, but does not enforce a rate
|
|
def monitor_time(self):
|
|
remaining = self._next_frame_time - sec_since_boot()
|
|
self._next_frame_time += self._interval
|
|
if remaining < -self._print_delay_threshold:
|
|
print self._process_name, "lagging by", round(-remaining * 1000, 2), "ms"
|
|
self._frame += 1
|
|
self._remaining = remaining
|
|
|