zfsdist(8)

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)