vfscount(8) System Manager's Manual vfscount(8)
NAME
vfscount - Count VFS calls ("vfs_*"). Uses Linux eBPF/bcc.
SYNOPSIS
vfscount [duration]
DESCRIPTION
This counts VFS calls. This can be useful for general workload charac-
terization of these operations.
This works by tracing all kernel functions beginning with "vfs_" using
dynamic tracing. This may match more functions than you are interested
in measuring: Edit the script to customize which functions to trace.
Since this uses BPF, only the root user can use this tool.
REQUIREMENTS
CONFIG_BPF and bcc.
OPTIONS
duration
duration of the trace in seconds.
EXAMPLES
Count some VFS calls until Ctrl-C is hit:
# vfscount
Count some VFS calls in ten seconds
# vfscount 10
FIELDS
ADDR Address of the instruction pointer that was traced (only useful
if the FUNC column is suspicious and you would like to double
check the translation).
FUNC Kernel function name
COUNT Number of calls while tracing
OVERHEAD
This traces kernel vfs functions and maintains in-kernel counts, which
are asynchronously copied to user-space. While the rate of VFS opera-
tions can be very high (>1M/sec), this is a relatively efficient way to
trace these events, and so the overhead is expected to be small for
normal workloads. Measure in a test environment, and if overheads are
an issue, edit the script to reduce the types of vfs functions traced
(currently all beginning with "vfs_").
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
vfsstat(8)
USER COMMANDS 2015-08-18 vfscount(8)
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