Re: C_CAN: can frame drops

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 07/25/2014 10:22 AM, Ssagarr Patil wrote:
> Hi Marc,
> 
>>
>> On 07/25/2014 10:13 AM, Ssagarr Patil wrote:
>>>>> I am using the c_can driver for latest kernel and using the latest canutils to dump to a file.
>>>>> My can bus is set at a rate of 1Mb (receiving 7000fps bus load of 80%).
>>>>>
>>>>> When I use the candump tool to dump can frames I get following message,
>>>>>
>>>>> 'DROPCOUNT: dropped 2223 CAN frames on 'any' socket (total drops 1629092)'
>>>>
>>>> These are the CAN frames dropped by the socket, this means as Oliver
>>>> pointed out, that the candump fails to read the CAN frames fast enough
>>>> from the socket. How do you connect to the linux box with the c_can?
>>>> Where are the CAN frames printed to?
>>>>
>>> Agreed this is dropped by the socket, so for this to solve I increased the socket size
>>> (with -r option of candump to 111173056) after doing this I see that there is frame drop in
>>> the driver ie I see this function c_can_handle_lost_msg_obj() being called frequently in which
>>> can frame is overwritten.
>>>
>>> I have a can frame generator which I have connected to the EVM, the EVM is recieving the
>>> frames and just dumping it on stdout going ahead I need to log the canframes to SD card.
>>
>> ...and where is your stdout going? serial line, telnet, ssh?
>>
> Its the serial line.

That's not good. As printing to the serial console is quite costly.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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