Difference between revisions of "Feb 2013"
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To check if disk is a limitation, I turned off writing to disk in the coda config. And I still see these errors. So disk may not be an issue. (adaq1 has 1.1 GB/sec speed) | To check if disk is a limitation, I turned off writing to disk in the coda config. And I still see these errors. So disk may not be an issue. (adaq1 has 1.1 GB/sec speed) | ||
| − | Next is the network. We have 100MBits/sec (12.5 MBytes/sec). How can we max out at 5K Bytes/sec? | + | Next is the network. We have 100MBits/sec (12.5 MBytes/sec). How can we max out at 5K Bytes/sec? How can I turn off transfer through the network (instead write to local memory) to check the limitation? |
| + | |||
| + | I tried this by replacing dma_dabufp in faRead() with dummy pointer to local memory, but I could not make it work yet. I am still seeing these errors (although now the raw data contains full of 0x000000s) | ||
Revision as of 17:24, 6 February 2013
Date : 6 Feb 2013 (K.Allada)
We are now using the new FADC(v2) and a fixed pulser.
I did few more checks to find out why we are getting "data not ready" errors at trigger rates beyond ~250KHz (with PTW =75 samples). This is related to datascan becoming zero for few-tens-of-events/100 triggers, and this becomes worse as we go to higher trigger rates. When this happens the event is empty. And since we do blocking, we get a empty blocks. Blocksize is 100.
Also, note that the theoretical limit (from the excel sheet) with PTW=75 samples and FADC v2 is around ~430 kHz. We should be able to take this much rate with a fixed pulser.
From the routine tiSetTriggerHoldoff(1,40,0), the trigger limit, without additional deadtime, is 40*16=640ns (= 1.56MHz). So this is fine...we are not there yet.
Below is a table showing observed data rate from the Run Control GUI for different trigger rates. It seems like the data rate is saturating at ~5K Bytes/sec ( which is around 250 KHz) and that's when the datascan becomes zero (error).
run trigger rate observed event rate observed data rate error condition 1910 31 kHz 31 kHz ~600 Bytes/sec no error 1909 85 kHz 85 kHz ~1500 Bytes/sec no error 1908 121 kHz 121 kHz ~2200 Bytes/sec no error 1907 168 kHz 168 kHz ~3000 Bytes/sec no error 1906 251 kHz 251 kHz ~5000 Bytes/sec no error 1905 315 kHz 315 kHz ~5200 Bytes/sec error 1904 434 kHz 434 kHz ~5200 Bytes/sec error
To check if disk is a limitation, I turned off writing to disk in the coda config. And I still see these errors. So disk may not be an issue. (adaq1 has 1.1 GB/sec speed)
Next is the network. We have 100MBits/sec (12.5 MBytes/sec). How can we max out at 5K Bytes/sec? How can I turn off transfer through the network (instead write to local memory) to check the limitation?
I tried this by replacing dma_dabufp in faRead() with dummy pointer to local memory, but I could not make it work yet. I am still seeing these errors (although now the raw data contains full of 0x000000s)
