"shogun" <[email protected]> wrote:
Your assumption is correct about the performance it less than I expected.
Sending a data block 2894 bytes every 200mS is 14.5kBytes/sec and it works
at that rate. It appears the fastest I can send that block of data is
about
every 100mS and that is about 28.9k Bytes per second. If I try to send
the
2894 byte block every 90mS the send starts failing after 3-4 sends and the
send returns an out of memory error. At 90mS, that is only
25.7kBytes/sec.
These rates should be easy for a 10MBit connection and I am running a
100MBit connection. I know the CPU can affect the performance but I am
running a 32 bit arm Cortex M# at 80MHz. Is this typical performance from
lwip on a TCPIP connection?
I can't comment on expected performance for your platform (I would expect it
to be higher), but there may be other factors influencing your throughput.
Two major factors will be the window size being offered by the receiver, and
the amount of buffer space and send queue length in LWIP. If the other
device starts by offering a small window, then you will only be able to send
as much data as that window before LWIP will have to stop sending and wait
for an acknowledgement to arrive. At this point, if you keep supplying
transmit data to LWIP, it will be filling its buffers while unable to send
anything. If you haven't configured LWIP to allow sufficient buffered
transmit data then this will result in out of memory errors.
After a TCP connection is established, it may take a little while for it to
stabilise with a steady flow of data, so the problem may be as simple as
increasing the relevant buffers to allow LWIP to hold more data at the start
of the connection.
The only information you have supplied so far showing the data transmission
pattern implies your device can send 2894 bytes in three packets within
approximately 200 microseconds. That's about 14 MB/s but only in a short
burst.
We may be able to provide more specific help if you could attach a wireshark
capture which shows the case where you are trying to send data every 90 ms
and errors are occurring. A copy of your lwipopts.h file might also provide
some relevant clues.
On another note, what do I have to be careful of in regards to lwip not
being reentrant?
If you are using the sockets or netconn API, don't use the same socket or
netconn from multiple threads. If you are using the raw API, don't allow the
LWIP core to be invoked from two threads (or from an interrupt handler and
main code simultaneously).
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