Re: C_CAN: can frame drops

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

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On 07/31/2014 02:41 PM, Ssagarr Patil wrote:
> Hi Oliver,
> 
> Sorry for the delayed response! was busy with other work load.
> 
>>
>>>>>> If you want to log all CAN
>>>>>> messages, you can probably make use of recvmmsg() to receive more than
>>>>>> one CAN frame at a time (instead of using recvmsg() or read()). When
>>>>>> writing to disk, don't write a single CAN frame at a time, it's better
>>>>>> to write large blocks, i.e. several 4k of data.
>>>>>>
>>>>> I am using the v3.16 (the master branch from git://gitorious.org/linux-can/linux-can.git)
>>>>>
>>>>> OK will try experiment with recvmmsg() & and writing to disk with large blocks.
>>>>>
>>>>
>>>> I implemented a proof-of-concept for recvmmsg() for candump.
>>>>
>>>> You can try:
>>>>
>>>> https://gitorious.org/linux-can/canpump
>>>>
>>>
>>> Any plans of adding this into mainline can-utils ?
>>>
>>
>> Hm - currently not.
>>
>> If it turns out to really help to increase the throughput for e.g. candump it
>> would be worth thinking to integrate it into candump.
>>
>> But so far there was no feedback from Sagar, if it was at least helpful.
>>
> Yes it was beneficial I used MSG_WAITALL flag for recvmmsg() so that 
> it waits for n frames and there is no memory wastage.
> 
> Also is it possible to configure qdiscs for improving the performance ?

AFAIK qdiscs are only used in the tx path.

Marc

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