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

Outline Lab Setup Hardware Tools Measurements Looking Forward

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 E5630 2.53GHz (16 processors) Cache: L1 is 256 kB L2 is 1024 kB L3 is 12288 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

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

Test Structure GPU1 PCATE LKRPN0

Latency GPU1PCATE

Opposite Way (PCATEGPU1)

Busy Script Running on Same CPU PCATEGPU1

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

Latency GPULKRPN0

Opposite Way (LKRPN0GPU) Interesting and Unexpected!

Latency PCATELKRPN0

Opposite Way (LKRPN0PCATE)

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)