.TH xfsdist 8  "2018-09-08" "USER COMMANDS"
.SH NAME
xfsdist.bt \- Summarize XFS operation latency. Uses bpftrace/eBPF.
.SH SYNOPSIS
.B xfsdist.bt
.SH DESCRIPTION
This tool summarizes time (latency) spent in common XFS file operations: reads,
writes, opens, and syncs, and presents it as a power-of-2 histogram. It uses an
in-kernel eBPF map to store the histogram for efficiency.

Since this works by tracing the xfs_file_operations interface functions, it
will need updating to match any changes to these functions.

Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bpftrace.
.SH EXAMPLES
.TP
Trace XFS operation time, and print a summary on Ctrl-C:
#
.B xfsdist.bt
.SH FIELDS
.TP
0th
The operation name (shown in "@[...]") is printed before each I/O histogram.
.TP
1st, 2nd
This is a range of latency, in microseconds (shown in "[...)" set notation).
.TP
3rd
A column showing the count of operations in this range.
.TP
4th
This is an ASCII histogram representing the count column.
.SH OVERHEAD
This adds low-overhead instrumentation to these XFS operations,
including reads and writes from the file system cache. Such reads and writes
can be very frequent (depending on the workload; eg, 1M/sec), at which
point the overhead of this tool may become noticeable.
Measure and quantify before use.
.SH SOURCE
This is from bpftrace.
.IP
https://github.com/iovisor/bpftrace
.PP
Also look in the bpftrace distribution for a companion _examples.txt file containing
example usage, output, and commentary for this tool.

This is a bpftrace version of the bcc tool of the same name. The bcc tool
may provide more options and customizations.
.IP
https://github.com/iovisor/bcc
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Brendan Gregg
.SH SEE ALSO
biolatency(8)