NAME¶

syncsnoop.bt - Trace the sync() variety of syscalls. Uses bpftrace/eBPF.

SYNOPSIS¶

syncsnoop.bt

DESCRIPTION¶

syncsnoop traces calls to sync() syscalls (sync(), fsync(), msync(), etc), which flushes file system cache and buffers to storage devices. These calls can cause performance perturbations, and it can be useful to know if they are happening, when they happen, and how frequently.

This works by tracing the sync() variety of syscalls via tracepoints.

This program is also a basic example of eBPF/bcc.

Since this uses BPF, only the root user can use this tool.

REQUIREMENTS¶

CONFIG_BPF and bpftrace.

EXAMPLES¶

Trace calls to sync() syscalls:

# syncsnoop.bt

FIELDS¶

TIME

A timestamp on the output, in "HH:MM:SS" format.

PID

The process ID that was on-CPU during the event.

COMM

The process name that was on-CPU during the event.

EVENT

The tracepoint name for the sync event.

OVERHEAD¶

This traces sync syscalls and prints output for each event. As the rate of this is generally expected to be low (<< 100/s), the overhead is also expected to be negligible.

SOURCE¶

This is from bpftrace.

https://github.com/iovisor/bpftrace

Also look in the bpftrace distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.

This is a bpftrace version of the bcc tool of the same name.

https://github.com/iovisor/bcc

OS¶

Linux

STABILITY¶

Unstable - in development.

AUTHOR¶

Brendan Gregg

SEE ALSO¶

iostat(1)