NAME¶

vfsstat - Statistics for some common VFS calls. Uses Linux eBPF/bcc.

SYNOPSIS¶

vfsstat [interval [count]]

DESCRIPTION¶

This traces some common VFS calls and prints per-second summaries. This can be useful for general workload characterization, and looking for patterns in operation usage over time.

This works by tracing some kernel vfs functions using dynamic tracing, and will need updating to match any changes to these functions. Edit the script to customize which functions are traced. Also see vfscount, which is more easily customized to trace multiple functions.

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

REQUIREMENTS¶

CONFIG_BPF and bcc.

EXAMPLES¶

Print summaries each second:

# vfsstat

Print output every five seconds, three times:

# vfsstat 5 3

FIELDS¶

READ/s

Number of vfs_read() calls as a per-second average.

WRITE/s

Number of vfs_write() calls as a per-second average.

CREATE/s

Number of vfs_create() calls as a per-second average.

OPEN/s

Number of vfs_open() calls as a per-second average.

FSYNC/s

Number of vfs_fsync() calls as a per-second average.

OVERHEAD¶

This traces various 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.

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

AUTHOR¶

Brendan Gregg

SEE ALSO¶

vfscount(8)