biolatpcts_example.txt

Demonstrations of biolatpcts.py, the Linux eBPF/bcc version.


This traces block I/O and uses layered percpu arrays to bucket the completion
latencies. Latency percentiles are calculated periodically from the buckets.

# ./biolatpcts.py
p50=595.0us p75=685.0us p90=1500.0us p99=2500.0us
p50=55.0us p75=95.0us p90=305.0us p99=2500.0us
p50=385.0us p75=655.0us p90=1500.0us p99=2500.0us
[...]

The latency is measured from I/O request to the device, to the device
completion. This excludes latency spent queued in the OS.

This is a simplified example to demonstrate the calculation of latency
percentiles. See tools/biolatpcts.py for the full utility.