Inconsistent behavior of `get_messages` on Linux and Windows

pierreluctg commented 4 years ago

Hi, we are observing a very large delay between Tx and Rx (of that same Tx message) on Linux when using libicsneo legacy API.

I have attached a code example showing the issue. On windows this is results in a tx+rx delay mean time of about 0.0025 sec. on Linux we get about 1 sec.

This means that on Linux sending a message (CAN in our case) and receiving that same message on the same CAN adapter and same network takes about 1 seconds. This is, as you know a eternity.

The code attached basically send a message with the current time in the data portion, then receive that same message and compare the time stored in data (Tx time) and the current time (Rx time).

Can you please have a look.

Let me know if you need any additional information.

import struct
import time
from itertools import cycle
from statistics import mean, stdev

import ics

def tx(device):
    message = ics.SpyMessage()
    message.NetworkID = ics.NETID_HSCAN
    message.ArbIDOrHeader = 0x001
    message.NumberBytesData = 8
    ts = time.time()
    ba = bytearray(struct.pack("d", ts))
    message.Data = tuple(ba[:8])
    ics.transmit_messages(device, message)
    return ts

def rx(device):
    rx_message = None
    while rx_message is None:
        messages, errors = ics.get_messages(device, False, 1)
        for ics_msg in messages:
            is_tx = bool(ics_msg.StatusBitField & ics.SPY_STATUS_TX_MSG)
            if not is_tx:
                continue
            if bool(ics_msg.StatusBitField & ics.SPY_STATUS_GLOBAL_ERR):
                continue

            if ics_msg.ArbIDOrHeader == 0x001:
                rx_message = ics_msg

    return struct.unpack("d", bytearray(rx_message.Data))[0]

def tx_rx(device):
    tx_ts = tx(device)
    rx_ts = rx(device)
    tx_rx_time = time.time() - rx_ts

    # Confirm that we are looking at the right message
    assert tx_ts == rx_ts
    print(f"Tx and Rx took {tx_rx_time} seconds")
    return tx_rx_time

def main():
    devices = ics.find_devices()
    device = devices[0]
    print(device)
    ics.open_device(device)

    deltas = []
    for _ in range(1000):
        deltas.append(tx_rx(device))

    ics.close_device(device)

    print("=" * 20)
    print(f"Min: {min(deltas)}, Max: {max(deltas)}")
    print(f"Mean: {mean(deltas)}, Std: {stdev(deltas)}")

if __name__ == '__main__':
    main()

pierreluctg commented 4 years ago

Hi @drebbe-intrepid, please have a look.

I will also post a PR with a fix.

pierreluctg commented 4 years ago

Please see PR #85