Reports and Measurements

This page serves to collect reports and measurements on the GMT.

Booster Test

Timing Receivers

White Rabbit Network

MPS Tests

Other

The Unofficial Feature List (Out of Date)

Although the subject is extremely complex, it is tried to summarize the status of some key characteristics of the GMT in the following table. It is intended to give safe (worst case) values of the actual performance including a reference; same for the specification. Values are taken at various conditions that might not be representative.

Sub-System Item Stat Reported Value Specified Value Date Rep (Spec) Ref Rep (Spec) Remark
OS              
CentOS RT: task switching latency DONE 100 us (ub), 20 us (av) < 1 ms (?) 09/2018 (<2010 ?) priv comm. from HEL (SR) measurement on SCU using preempt-test, only 3us gain without hyperthr
Timing Receiver              
FTRN userland latency @ API DONE 93 us (ub), 62 us (av) < 1 ms (?) 12/2012 (<2010 ?) article (N/A) 1 ms spec is overal FEC performance
FTRN userland latency @ saftlib ALERT! 2500 us (ub), 1400 us (av) < 1 ms (?) 11/2017 (<2010 ?) wiki (N/A) 1 ms spec is overal FEC performance, ok for 2018
FTRN output (Lemo) jitter (RMS) DONE 20 ps (av) 100 ps 11/2014 (01/2013) article (F-DS-C-06e) 'term jitter' defined in F-DS-C-05e
FTRN output (Lemo) precision (RMS) DONE 50 ps (av) 1 ns 11/2014 (01/2013) article (F-DS-C-06e) 'term precision' defined in F-DS-C-05e
FTRN output (Lemo) accuracy (RMS) DONE ok, needs re-checking with every release 2-3 ns 11/2014 (01/2013) wiki (F-DS-C-06e) 'term accuracy' defined in F-DS-C-05e
Timing Network              
upper bound latency DONE < 390 us @ 4 WRS layers 500 us [1] 06/2016 (2012 ?) report (minutes, wiki) F-DS-C-05e mentions '200 us' as 'should'
throughput (messages) DONE > 16 messages @ 500 us (sl) 16 msg. @ 500 us (sl) 12/2017 (12/2017) Dry Run #3 ( minutes )  
throughput (frame size) ALERT! < 60 MBit/s 100 MBits/s 08/2016 (09/2014) report (wiki) 1 to N ports @ 64 bytes/frame, ok for 2018
loss rate ALERT! < 2e-8 @ 600 Hz msg. rate 1e-12 08/2016 (01/2013) wiki (F-DS-C-05e) without forward error correction, ok for 2018
loss rate ALERT! > 90% @ > 10% bandwidth 1e-12 08/2016 (01/2013) wiki (F-DS-C-05e) for small packets of 64 and 128 bytes. Better for larger packets.
max numbers of WRS layers DONE 4 5 06/2016 (2012 ?) report (various minutes) maybe 4 layers are sufficient
Data Master @2018              
upper bound latency per lm32 CPU DONE < 500 us @ 16 msg (sl) 500 us [2] (sl) 12/2017 (12/2017) minutes (./.) update 2018-sep-03: max reported upper latency is 505 us
throughput per lm32 CPU DONE > 16 messages @ 500 us 16 msg. @ 500 us 12/2017 (12/2017) minutes (./.)  
capacity per lm32 CPU processing 600 msg @ 2018 600 msg @ 2018 12/2017 (12/2017) minutes (./.) 1 control block 'eats' 11msg
number of patterns lm32 CPU processing 4 @ 2018 > 10 ? 12/2017 (12/2017) minutes (N/A) not really specified; 4 patterns ok for 2018
number of lm32 CPU ALERT! 3 8 ? 12/2017 (2012 ?) minutes (N/A) not really specified; 3 cores ok for 2018
Table: Status of key characteristics of the GMT. Some values are marked by upper bound (ub), or average (av) or sliding window (sl).

[1] The Data Master sends messages to the White Rabbit network 500 us ahead of their scheduled time. The budget of 500 us includes the processing time in the timing receiver. [2] The upper bound latencies of the network and the data master must be added. It was decided to use a total upper bound latency of 1 ms for the 2018 beam time. Update: The '1ms upper bound' is kept for the 2019 und 2020 beam times.

-- DietrichBeck 22 April 2024
I Attachment Action Size Date Who Comment
WR_Switch_RFC_2889.pdfpdf WR_Switch_RFC_2889.pdf manage 1 MB 08 Sep 2016 - 08:12 UnknownUser  
report_gsi_use_case_wrs_v6.1.pdfpdf report_gsi_use_case_wrs_v6.1.pdf manage 589 K 01 Feb 2024 - 13:36 EnkhboldOchirsuren performance evaluation of the White Rabbit timing network
Topic revision: r37 - 22 Apr 2024, DietrichBeck
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