RE: C_CAN: can frame drops

[Ssagarr Patil <hugarsagar@outlook.com>]

Hi Marc,

Thanks for the response!
>
> 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.
>
Yes agreed, although I also see some frame drops pointed by ifconfig can0
when dumping it to file (with -l option of candump)
I have also used chrt to increase the priority of candump.

Any suggestion on how to still improve the performance so as there is zero frame loss ?
either on driver or application side.

Thanks,
--Sagar