You must measure RDMA latency between two hosts. What do you run?
Why A is the answer
ib_write_lat
This perftest measures latency.
In detail
- ib_write_lat measures RDMA latency.
- It is a perftest tool.
Use case
An illustrative scenario, not a real incident.
A team checks RDMA latency with ib_write_lat.
See it in different ways
flowchart TD
A{"What do you want to know?"} -->|"Local port state"| B["ibstat"]
A -->|"Which nodes exist"| C["ibnodes"]
A -->|"Link details"| D["iblinkinfo"]
A -->|"Fabric errors"| E["ibdiagnet"]
A -->|"RDMA speed"| F["ib_write_bw and ib_write_lat"]stateDiagram-v2 [*] --> LocalPort: ibstat LocalPort --> Fabric: ibnodes and iblinkinfo Fabric --> Errors: ibdiagnet Errors --> Path: ibping Path --> Speed: ib_write_bw and ib_write_lat Speed --> [*]
flowchart TD
Q{"What are you measuring?"}
Q -->|"Bandwidth"| A0["ib_write_bw"]
Q -->|"Latency"| A1["ib_write_lat"]Key point: ib_write_lat measures latency.
Why the other options are wrong
- B. ib_write_bw
- That measures bandwidth.
- C. iblinkinfo
- That shows link details.
- D. ibstat
- That shows a local port.