Imre Paniti wrote: > 2006/8/16, Jan Kiszka <[EMAIL PROTECTED]>: >> >> Imre Paniti wrote: >> > 2006/8/16, Jan Kiszka <[EMAIL PROTECTED]>: >> >> >> >> Imre Paniti wrote: >> >> > 2006/8/14, Jan Kiszka <[EMAIL PROTECTED]>: >> >> >> >> >> >> Imre Paniti wrote: >> >> >> > We want to test our RTnet aplication to see if the timing is >> right. >> >> >> >> >> >> What timing? On the cable? >> >> > >> >> > >> >> > The time difference between sending and reciving. >> >> > >> >> >> Actually we find a page for Active Probing at >> >> >> > >> >> >> http://www.cubinlab.ee.unimelb.edu.au/probing/software.php#tsc-rt-linux >> >> >> > but they dealing with RTnet based on RTLinux. >> >> >> > Our environment: 2 PC with 2.6.15 kernel, RTAI-3.3-cv and RTnet >> >> 0.9.3 >> >> >> > The NICs are RT8139. >> >> >> > >> >> >> > Do you have some suggestions for us? >> >> >> >> >> >> Do you have a chance to attach a third station as a sniffer to your >> >> >> network (works best with one of the rare 100 MBit hubs...)? Then >> >> >> grabbing the traffic with RTnet+RTcap on that box would give you a >> >> good >> >> >> impression with accurate timestamps (in the order of IRQ >> latencies). >> >> >> >> >> >> Jan >> >> > >> >> > >> >> > Thanks for the idea! >> >> > We can do that, but what about using RTnet+RTcap (+Ethereal as a >> >> capturing >> >> > tool) on those PCs without a third station? >> >> >> >> Also feasible. You just have different clocks then. And you see things >> >> like the stations see them. If you plan to load the boxes in order to >> >> generate worst case behaviour, your locally taken timestamps will >> suffer >> >> as well. Therefore the idea of a third station dedicated to measuring. >> >> >> >> Jan >> > >> > >> > I think I get it - with a third station we can measure the performance >> of >> > RTnet under high pressure, sending loads of data with a static interval >> and >> > see how much this interval differs from the interval with which our >> sniffer >> > sees a packet. Is that right? If it is, that is not really what we're >> > looking for. We're trying to find a way to see how RTnet affects our >> > real-time thread - while sending much data and little data, and with a >> busy >> > thread and a less busy thread. If possible, then how would a third >> machine >> > sniffer deal with that? Or would there be an other solution? >> >> Ah, I see. Then you are looking for something like LTTng (currently not >> supported over Adeos/I-pipe unfortunately, will come) or the latency >> tracer (http://download.gna.org/adeos/patches/v2.6/i386/tracer/). >> >> The latter can be used to record the maximum IRQs-off period and to >> trigger a back-trace from your application when it detects a high delay. >> This happens at kernel-level by logging every function entry with a >> timestamp. It also supports recording of PIDs which can be used to trace >> context switches, but RTAI doesn't make use of this yet. Note that, as >> the tracer degrades the performance of the target, its numbers are not >> directly transferable to the production system. To sum up, the tracer is >> specifically useful for finding long preemption locks and analysing >> scenarios that can be detected as critical at application level (e.g. a >> deadline miss). >> >> Don't know, maybe RTAI also provides an overview of the CPU load each RT >> thread consumes. Check /proc/rtai. This may give a rough impression of >> the average system load. We have such stuff in Xenomai since recently, >> but I do not have numbers of the RTnet threads (stack manager, TDMA, >> RTcfg) at hand. >> >> Jan > > > Thank You for Your help! > I'm afraid that we can not workaround the kernel patching, or? >
I didn't get the problem yet. The tracer is a kernel patch, correct, but it should apply without problems also on top of RTAI's I-pipe patch variant. Or what patching do you mean? Jan
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