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 characterization 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 operations 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