1. Latency Measurement Testing
John Kroon, G. Lamanna, R. Fantechi
12/07/2011

2. Outline
Lab Setup
Hardware Tools
Measurements
Looking Forward

3. Hardware Adapter for Parallel port PCATE is a Pentium 4 2.4GHz
Cache: L1 is 8 kB
L2 is 512 kB (no L3)
GPU1 is a 2*4 core Xeon E GHz (16 processors)
Cache: L1 is 256 kB
L2 is 1024 kB
L3 is kB
Direct Ethernet connection on hidden network
Each PC has a Parallel port I/F used for generating timing pulses
Lecroy Scope for:
Time measurements
Histograms
Save screenshots
PCATE
GPU1
Adapter for Parallel port

4. Hardware LKRPN0 is a Intel Xeon 2.0GHz (2 processors) Cache
L1: 4096 kB
L2: 64 kB
LKRPN0

5. Test Structure
GPU1
PCATE
LKRPN0

6. Latency GPU1PCATE

7. Opposite Way (PCATEGPU1)

8. Busy Script Running on Same CPU
PCATEGPU1

9. Selected Points 50 microsec pulse Package Size (Bytes) CPU Not Busy
CPU Busy
∆t=Busy – Not Busy
300
60.6
58.8
-1.8
700
66.7
64.9
1100
71.3
69.2
-2.1
30 microsec pulse
Package Size (Bytes)
CPU Not Busy
CPU Busy
∆t=Busy – Not Busy
300
50.8
49.9
-0.9
700
61.5
59.3
-2.2
1100
70.1
69.0
-1.1

10. Latency GPULKRPN0

11. Opposite Way (LKRPN0GPU)
Interesting and Unexpected!

12. Latency PCATELKRPN0

13. Opposite Way (LKRPN0PCATE)

14. Future Testing
We will investigate the latency after changing various Kernel settings using “sysctl” and/or “insmod”
Swappiness?
Further tests on latencyCache is important?
Test latency over different protocols (TCP,etc.)
Test with TELL1 (FPGA)