btrfsdist(8) System Manager's Manual btrfsdist(8)
NAME
btrfsdist - Summarize btrfs operation latency. Uses Linux eBPF/bcc.
SYNOPSIS
btrfsdist [-h] [-T] [-N] [-d] [interval] [count]
DESCRIPTION
This tool summarizes time (latency) spent in common btrfs 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 btrfs_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 bcc.
OPTIONS
-h Print usage message.
-T Don't include timestamps on interval output.
-m Output in milliseconds.
-p PID Trace this PID only.
EXAMPLES
Trace btrfs operation time, and print a summary on Ctrl-C:
# btrfsdist
Trace PID 181 only:
# btrfsdist -p 181
Print 1 second summaries, 10 times:
# btrfsdist 1 10
1 second summaries, printed in milliseconds
# btrfsdist -m 1
FIELDS
msecs Range of milliseconds for this bucket.
usecs Range of microseconds for this bucket.
count Number of operations in this time range.
distribution
ASCII representation of the distribution (the count column).
OVERHEAD
This adds low-overhead instrumentation to btrfs writes and fsyncs, as
well as all system reads and opens (due to the current implementation
of the btrfs_file_operations interface). Particularly, all reads and
writes from the file system cache will incur extra overhead while trac-
ing. Such reads and writes can be very frequent (depending on the work-
load; eg, 1M/sec), at which point the overhead of this tool may become
noticeable. Measure and quantify before use.
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
btrfsslower(8)
USER COMMANDS 2016-02-15 btrfsdist(8)
Generated by dwww version 1.16 on Tue Dec 16 05:45:59 CET 2025.