1. PowerPC / Intel Benchmark
Reflective Memory Recorder Upgrade: an opportunity to benchmark PowerPC and Intel architectures for real time. Roberto Abutera, Helmut Tischera, Robert Frahma aEuropean Southern Observatory,
07/11/2018
PowerPC / Intel Benchmark

2. PowerPC / Intel Benchmark
History & Status
mvme167 SBC based on 68k MPC MHz (1979)
mvme2600 SBC based on MPC MHz (1994)
mvme2700 SBC based on the MPC MHz (1997)
mvme6100 SBC based on the MPC GHz ( 2001)
Used on
~300 computers
Small fraction hard real time requirements, rest pseudo-real time
07/11/2018
PowerPC / Intel Benchmark

3. Why do we need new/more powerful CPUs
In fast control loops :
Reduce latency & pure computational delays => dramatically improve control system bandwidth
Simplify software architecture ( less asynchronous, less distribution, less communication requirements, etc )
And in general:
Confront imminent obsolescence.
Improve heat dissipation per unit of processing (6100 .aka. VME toaster)
Improve systems response time
Support , newer, more demanding applications ( wavefront control, huge detectors arrays, interferometry, etc)
07/11/2018
PowerPC / Intel Benchmark

4. Why do we need new more powerful CPUs
Dramatic effect of computational delay in control loops.
07/11/2018
PowerPC / Intel Benchmark

5. PowerPC / Intel Benchmark
Benchmark Hardware
PowerPC
MVME6100, MPC7457 PowerPC, GHz, VME, 0.5 GB RAM
Gigabit Ethernet.
GE Reflective Memory PMC-5565
Cost : ~6000 Euros
Intel MultiCore:
Intel Core i7 E , 2.8 GHz, 4 Cores, PCIExpress,12 GB RAM
Cost : ~1400 Euros
07/11/2018
PowerPC / Intel Benchmark

6. Benchmark Application
VLTI Reflective Memory Network Recorder
Based on a VxWorks real time operating system.
Based on the standard VLT instrument software framework.
Sequence of DMA read access to sparse pieces of reflective memory.
Streaming collected data up to 0.5 Gigabit/second.
Tasks :
trfmCtrl : DMA read Reflective Memory into the local memory.
trfmXfer : Transfer data from memory to remote system via TCP/IP.
tNet0 : system network stack task.
trfmMon: background task running a 1 Hz.
07/11/2018
PowerPC / Intel Benchmark

7. PowerPC / Intel Benchmark
07/11/2018
PowerPC / Intel Benchmark

8. RMN recorder configurations
Fragmented Configuration 10 KHz leading to a transfer rate of 68.3 Mbit/sec.
07/11/2018
PowerPC / Intel Benchmark

9. RMN recorder configurations
Big Data 10 KHz leading to a transfer rate of 290 Mbit/sec.
07/11/2018
PowerPC / Intel Benchmark

10. PowerPC / Intel Benchmark
Cycles to benchmark
Read-in cycle ( Control task)
Awake by interrupt of system clock
Sequential DMA accesses.
Few µsec available ( cycle frequency )
Can’t be delayed beyond µsec budget without losing samples.
Higher priority
Transfer cycle ( Transfer + Network tasks) :
Awake when read-in cycles buffers are filled ( .i.e. 3 seconds)
TCP/IP socket data transfer
Can be delayed within 3 seconds as long as the full buffer is transmitted in the available 3 seconds.
Lower priority
07/11/2018
PowerPC / Intel Benchmark

11. Read-in cycle - PowerPC - 10KHz - Fragmented
07/11/2018
PowerPC / Intel Benchmark

12. Read-in cycle - Intel (1 core) 10KHz - Fragmented
07/11/2018
PowerPC / Intel Benchmark

13. Transfer cycle – PowerPC - 10KHz - Fragmented
07/11/2018
PowerPC / Intel Benchmark

14. Transfer cycle – Intel (1 core) - 10KHz - Fragmented
07/11/2018
PowerPC / Intel Benchmark

15. Read-in cycle – PowerPC - 16KHz - Fragmented
Read-in cycle ( Control task) unable to execute in 62 µsec leads to :
Loose of data or
Crash of the computer.
Possibilities to overcome this :
Redesign the map of the reflective memory to reduce fragmentation => high development and integration costs .i.e. affects many systems.
Reprogram the reflective memory driver to have chained DMA access=>high development and complex maintenance
07/11/2018
PowerPC / Intel Benchmark

16. Read in cycle – Intel (1 core) - 16KHz – Big Data
07/11/2018
PowerPC / Intel Benchmark

17. Read in + Transfer cycle – Intel MultiCore - 16KHz – Big Data
07/11/2018
PowerPC / Intel Benchmark

18. PowerPC / Intel Benchmark
% Idle Time
16 KHz on PowerPC not possible.
MultiCore , on both configurations and frequencies remains mainly IDLE.
07/11/2018
PowerPC / Intel Benchmark

19. PowerPC / Intel Benchmark
Conclusions
RMN recorder range of operation can be extended to at least 16 KHz by moving to Intel MultiCore.
As expected, VxWorks isolates application software from hardware architecture. Low migration cost.
Performance scales with available CPU power and I/O bandwidth.
Applications access to VME bus very slow.
Cost per CPU power unit is dramatically reduced moving from PowerPC to Intel MultiCore.
07/11/2018
PowerPC / Intel Benchmark