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Problems
========
- When streaming at high speed (~ 16 data streams; 600 Mbit & 600 kpck each), the data streams quickly get
desynchronized (but all packets are delivered).
* It is unclear if problem is on the receiver side (no overloaded CPU cores) or de-synchronization is first
appear on the simmulation sender. The test with real hardware is required.
* For border case scenarios, increasing number of buffers from 2 to 10-20 helps. But at full speed, even 1000s
buffers are not enough. Packets counts are quickly going appart.
* Further increase of packet buffer provided to 'recvmmsg' does not help (even if blocking is enforced until
all packets are received)
* At the speed specified above, the system works also without libvma.
* Actually, with libvma a larger buffer is required. In the beginning the performance of libvma is gradually
speeding up (that was always like that). And during this period a significant desynchronization happens. To
compensate it, we need about 400 buffers with libvma as compared to only 10 required if standard Linux
networking is utilized.
- In any case (LibVMA or not), some packets will be lost in the beginning if high-speed communication is tested.
* Usually, first packets are transferred OK, but, then, a few packets will be lost occasionally here and there
(resulting in broken frames). This basically breaks grabbing a few packets and exitig. Unclear if server- or
client-side problem (makes sense to see how real-hardware will behave).
* Can we pre-heat to avoid this speeding-up problem (increase pre-allocated buffers, disable power-saving
mode, ??) Or it will be also not a problem with hardware? We can send UDP packets (should be send from another
host), but packets are still lost:
for i in $(seq 4000 4015); do echo "data" > /dev/udp/192.168.34.84/$i; done
* The following doesn't help: new version of libvma, tunning of the options.
- Communication breaks with small MTU sizes (bellow 1500), but this is probably not important (Packets are
delivered but with extreme latencies. Probably some tunning of network stack is required).
- Technically, everything should work if we start UFO server when data is already streamed. However, the first
dataset could be any. Therefore, the check fails as the data is shifted by a random number of datasets.
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