---
name: "zfsdist-bpfcc"
section: "8"
platform: "linux"
package: "bpfcc-tools"
version: "0.31.0+ds-7"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/zfsdist-bpfcc"
---

# zfsdist-bpfcc(8)

Summarize ZFS operation latency. Uses Linux eBPF/bcc.

## NAME

zfsdist - Summarize ZFS operation latency. Uses Linux eBPF/bcc.

## SYNOPSIS

**zfsdist \[-h\] \[-T\] \[-m\] \[-p PID\] \[interval\] \[count\]**

## DESCRIPTION

This tool summarizes time (latency) spent in common ZFS 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.

This uses kernel dynamic tracing of the ZPL interface (ZFS POSIX Layer), and will need updates to match any changes to this interface.

- This is intended to work with the ZFS on Linux project:

  http://zfsonlinux.org

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 ZFS operation time, and print a summary on Ctrl-C:

  \# **zfsdist**

- Trace PID 181 only:

  \# **zfsdist -p 181**

- Print 1 second summaries, 10 times:

  \# **zfsdist 1 10**

- 1 second summaries, printed in milliseconds

  \# **zfsdist -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 these ZFS 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.

## 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

zfssnoop(8)