RAKOTOSALAMA, Nirilanto wrote: >>> Hello, >>> =20 >>> In order to test rtcap+wireshark perf to see if it could >> analize a full= >> loaded traffic, >>> I ran a simple program that sends n UDP packets of 1 kBytes >> from a box = >> (xenomai 2.3.1+ rtnet 0.9.9+ e1000) >>> to another (xenomai 2.3.1+ rtnet 0.9.9+ eepro100 + rtcap + >> wireshark). >>> Packets are sent without delay between each of them. >>> If more than 100 packets are sent, wireshark only shows 82 >> captured pac= >> kets and rt_sendmsg function doesn't=20 >>> return any error. >>> What could be the source of this loss ?=20 >>> Is it sure that packets are really sent ? Is there a means >> to know how = >> many packet did the NIC really send ? >>> Did rt_dev_sendmsg return error if NIC has not enough >> buffer space at d= >> river layer or below ? >> >> If you are sending at a very high rate, you may temporarily >> overload the >> sniffer. That may mean the RT queues overflow (not likely if >> both boxes >> have similar performance) or Linux fails to process all >> sniffed packets >> in time (because the RT load is too high. Check the drop counter under >> "ifconfig rteth0", maybe it is non-zero. Still, there are 128 >> buffers in >> the rtcap pool by default (module parameter "rtcap_rtskbs" or >> rtcap.ko). >> Also check if there are any suspicious error messages on any kernel >> console of both boxes. > > Ok, it seems that wireshark is overloaded.
Try capturing offline, eg. with tcpdump into a file. > No suspicious kernel error message. > No packets are dropped neither in receiving nor sending box. > BTW, for both, only RX packets counter increases. RX counter of RTcap devices? Do they match your actual transmissions? > The TX packets counter doesn't increase for sending box, why ? If you are referring to the RTcap device: they do not transmit packets, they only receive what the RT NICs receive or send. > Moreover, when promisc mode is activated and > rtcap_rtskbs > number of sent packets, are the packets stored > until wireshark has time to process them ? Is there an other > buffer size to increase ? rtcap_rtskbs (see documentation) is the buffer space between RT and non-RT. If Linux does not have enough time to process sniffed packets (allocate Linux buffers and move data over), you will loose packets (avoiding that other RT applications run short on buffers). But that would be indicated in the rtcap device stats. Jan
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