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Diffstat (limited to 'src')
| -rw-r--r-- | src/DEVELOPMENT | 56 |
1 files changed, 0 insertions, 56 deletions
diff --git a/src/DEVELOPMENT b/src/DEVELOPMENT deleted file mode 100644 index 18a8011..0000000 --- a/src/DEVELOPMENT +++ /dev/null @@ -1,56 +0,0 @@ -Architecture -=========== - - Current implementation follows UFO architecture: reader and dataset-builder are split in two filters. - * The reader is multi-threaded. However, only a single instance of the builder is possible to schedule. - This could limit maximum throughput on dual-head or even signle-head, but many-core systems. - * Another problem here is timing. All events in the builder are initiaded from the reader. Consequently, - as it seems we can't timeout on semi-complete dataset if no new data is arriving. - * Besides, performance this is also critical for stability. With continuous streaming there is no problem, - however, if a finite number of frames requested and some packets are lost, the software will wait forever - for missing bits. - - -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. - - -Questions -========= - - Can we pre-allocate several UFO buffers for forth-comming events. Currently, we need to buffer out-of-order - packets and copy them later (or buffer everything for simplicity). We can avoid this data copy if we can get - at least one packet in advance. - - - How I can execute 'generate' method on 'reductor' filter if no new data on the input for the specified - amount of time. One option is sending empty buffer with metadata indicating timeout. But this is again - hackish. - - - Can we use 16-bit buffers? I can set dimmensions to 1/4 of the correct value to address this. But is it - possible to do in a clean way? - - - What is 'ufotools' python package mentioned in documentation? Just a typo? |