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• user "systemctl list-unit-files" to see if tdetsim.service or kcu.service is enabled
• associated .service files are in /usr/lib/systemd/system/
• to see if events are flowing from the hardware to the software: "cat /proc/datadev_0" and watch "Tot Buffer Use" counter under "Read Buffers"
• if you see the error "rogue.GeneralError: AxiStreamDma::AxiStreamDma: General Error: Failed to map dma buffers. Increase vm map limit: sysctl -w vm.max_map_count=262144".  This can be caused by that parameter being too low, but it can also be caused by loading the driver with CfgMode=1 in tdetsim.service (we use CfgMode=2).  This CfgMode parameter has to do with the way memory gets cached.
  • make sure the tdetsim.service is the same as another working node
  • make sure that the appropriate service is enabled (see first point)
  • check that the driver in /usr/local/sbin/datadev.ko is the same as a working node
  • check that /etc/sysctl.conf has the correct value of vm.max_map_count
• we have also seen this error when the datadev.ko buffer sizes and counts were configured incorrectly in tdetsim.service.
• For high rate running, many DMA buffers (cfgRxCount parameter) are needed to avoid deadtime. The number of DMA buffers is also used to size the DRPs' pebble, so slow but large DRPs like PvaDetector and EpicsArch need a comparatively small cfgRxCount value.  Neglecting to take this into account can result in attempting to allocate more memory than the machine has, resulting in the DRP throwing std::bad_alloc.
  
• DMA buffers can be small (cfgSize parameter) for most (all?) tdetsim applications.  16 KB is usually sufficient.  It must be larger than 4 KB or the driver throws and error.

An example tdetsim.service for an opal camera:

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