syncsnoop(8) System Manager's Manual syncsnoop(8)
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 4.4 feature (bpf_perf_event_output()); for
kernels older than 4.4, 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)
USER COMMANDS 2015-08-18 syncsnoop(8)
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