focal (8) syncsnoop-bpfcc.8.gz

NAME

       syncsnoop - Trace sync() syscall. Uses Linux eBPF/bcc.

SYNOPSIS

       syncsnoop

DESCRIPTION

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

       This works by tracing the kernel sys_sync() function using dynamic tracing, and  will  need  updating  to
       match any changes to this function.

       This  makes  use  of  a  Linux 4.5 feature (bpf_perf_event_output()); for kernels older than 4.5, see the
       version under tools/old, which uses an older mechanism.

       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 bcc.

EXAMPLES

       Trace calls to sync():
              # syncsnoop

FIELDS

       TIME(s)
              Time of the call, in seconds.

       CALL   Call traced.

OVERHEAD

       This traces the kernel sync function 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 bcc.

              https://github.com/iovisor/bcc

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

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       iostat(1)