> Evert Lammerts wrote:
>
>>> Imre Paniti wrote:
>>>
>>>
>>>> Hi,
>>>>
>>>>
>>>>
>>>> I'm getting a lot of ENOBUFS while repeatingly sending over 10
>>>> bytes of data data from a fast rt thread (100 packets per second). I
>>>> guess this makes
>>> I wouldn't consider 100 Hz as fast. Is this the correct rate? Or is
>>> the receiver overloaded and does some MAC layer overflow signalling?
>>
>> The rate is correct, and the reciever is probably not overloaded.
>>
>>
>>>> sense - no available buffers. But how does this work internally,
>>>> what happens with a que on a socket (we're using UDP, might a raw
>>>> socket be better?) when writing to it fast? I know we can increase
>>>> the buffer size, but that would only mean it fills up less fast but
>>>> still fills up. So on
>>>> the practical side of things, what can we do about this -105?
>>>>
>>>> We're using:
>>>> RTAI-3.3-CV
>>>> RTnet 0.9.3
>>>>
>>>>
>>> With or without RTmac? If /wo RTmac: which NIC driver? Switched
>>> Ethernet?
>>>
>>
>> This is lsmod after a simple start-up routine of RTnet:
>>
>>
>> emc2-2:~# lsmod
>> Module Size Used by
>> tdma 14852 1 rtmac 8976 1 tdma rtcfg
>> 37168 0
>> rt_loopback 2564 1 rt_8139too 11776 2 rtpacket
>> 4352 0
>> rtipv4 21536 1 rtcfg rtnet 29292 7
>> tdma,rtmac,rtcfg,rt_loopback,rt_8139too,rtpacket,rtipv4 rtai_rtdm
>> 16676 6 tdma,rtcfg,rt_8139too,rtpacket,rtipv4,rtnet
>> rtai_sem 15232 4 tdma,rtcfg,rtnet,rtai_rtdm rtai_up
>> 71736 8
>> tdma,rtcfg,rt_loopback,rt_8139too,rtipv4,rtnet,rtai_rtdm,rtai_sem
>> rtai_hal 29176 6
>> rtmac,rt_8139too,rtnet,rtai_rtdm,rtai_sem,rtai_up
>>
>> This means RTmac is used (right?). As you can see we're using a realtek
>> 8139 NIC.
>>
>>
>>>
>>> There are at least two error sources involved when sending out
>>> packets:
>>> first the per-socket pool of rtskbs that is charged when the outgoing
>>> frames are to be build. Later the NIC may report an overflow (EAGAIN)
>>> of its own hardware TX queue - unless you are using RTmac as flow
>>> control manager. This is true for both UDP and packet sockets.
>>
>> So I guess this means the error comes from rtskbs, because we're using
>> RTmac? If so, then what does that mean?
>>
>
> This means now that you do not provide enough bandwidth to your
> transmitter, thus it enqueues more packets then there are transmitted and
> runs out of buffers sooner or later.
>
> How does your TDMA configuration look like (see also
> /proc/rtnet/rtmac/tdma*? And how many other senders are sharing the
> transmission time slot(s) of the particular box?
There's only one sender.
I think I understand what you're saying. Stupid enough I didn't yet put
time into TDMA configuration - but I guess the error has to do with this
(?):
# Master parameters
# Simple setup: List of TDMA slaves
TDMA_SLAVES="192.168.1.100"
# Simple setup: Cycle time in microsecond
TDMA_CYCLE="5000"
# Simple setup: Offset in microsecond between TDMA slots
TDMA_OFFSET="200"
# Advanced setup: Config file containing all TDMA station parameters
# To use this mode, uncomment the following line and disable the
# three master parameters above (SLAVES, CYCLE, and OFFSET).
#TDMA_CONFIG="${prefix}/etc/tdma.conf"
The cycle time should be a lot faster, I guess? What about the offset? Or
do you recommend using the advanced set-up? If so, is there some
documentation around on that?
Thanks a bunch! It's great to have such easy and efficient communication
and support.
Evert
>
>>
>> It might be useful for you to take a look at my code. However, this is
>> for a module for CNC software (Enhanced Machine Controller 2, EMC2) and
>> it uses a custom RT API in combination with the RTnet and RTDM API,
>> which makes it a little harder to read. Apart from that, in the actual
>> functions that are exported as RT tasks, nothing really strange happens
>> - a socket
>> is created during module start-up, the RT tasks only either create
>> packets and send them or recieve packets and disect them.
>
> In fact, your problem should be independent of the actual application
> code.
>
> Jan
>
>
>
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