xfsdist.bt(8) System Manager's Manual xfsdist.bt(8)
NAME
xfsdist.bt - Summarize XFS operation latency. Uses bpftrace/eBPF.
SYNOPSIS
xfsdist.bt
DESCRIPTION
This tool summarizes time (latency) spent in common XFS file opera-
tions: 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 ef-
ficiency.
Since this works by tracing the xfs_file_operations interface func-
tions, it will need updating to match any changes to these functions.
Since this uses BPF, only the root user can use this tool.
REQUIREMENTS
CONFIG_BPF and bpftrace.
EXAMPLES
Trace XFS operation time, and print a summary on Ctrl-C:
# xfsdist.bt
FIELDS
0th The operation name (shown in "@[...]") is printed before each
I/O histogram.
1st, 2nd
This is a range of latency, in microseconds (shown in "[...)"
set notation).
3rd A column showing the count of operations in this range.
4th This is an ASCII histogram representing the count column.
OVERHEAD
This adds low-overhead instrumentation to these XFS operations, includ-
ing 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.
SOURCE
This is from bpftrace.
https://github.com/iovisor/bpftrace
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.
https://github.com/iovisor/bcc
OS
Linux
STABILITY
Unstable - in development.
AUTHOR
Brendan Gregg
SEE ALSO
biolatency.bt(8)
USER COMMANDS 2018-09-08 xfsdist.bt(8)
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