Tracing io_uring Request Latency and Ring Operations with bpftrace

This command executes an eBPF tracing script using bpftrace to measure the internal kernel latency of the io_uring_submit_req function in microseconds. The script attaches a kprobe at the entry of the kernel function to record a nanosecond timestamp indexed by thread ID, and a kretprobe at the return of the function to calculate execution duration. The calculated delta is stored in an eBPF log2 histogram map, providing real-time visibility into kernel submission queue processing overhead.

Performance engineers and SREs use this one-liner to diagnose sub-millisecond tail latencies and performance bottlenecks in asynchronous I/O pipelines. It helps determine whether I/O delays originate inside the kernel io_uring subsystem, driver queue depth limits, or physical storage devices, without modifying application source code or requiring binary re-compilation.

Attaching dynamic kernel probes (kprobes) introduces minimal CPU overhead per function invocation, making it safe for short-term diagnostic sessions in production environments. However, targeting frequently executed functions on system calls processing millions of IOPS can generate noticeable CPU overhead. Operators should limit trace duration and avoid running dynamic kprobes continuously on latency-sensitive production nodes.

> System.Execute()

bpftrace -e 'kprobe:io_uring_submit_req { @start[tid] = nsecs; } kretprobe:io_uring_submit_req /@start[tid]/ { @latency = hist((nsecs - @start[tid]) / 1000); delete(@start[tid]); } END { clear(@start); }'

> Architecture & Security Context

Verified for Valters IT Hub. When deploying this configuration in a production homelab or enterprise environment, ensure that you monitor system resources and implement strict access controls. Administrator privileges are required.

ID: VALTERSIT-D45CAF82AB70