Man page - zfsdist-bpfcc(8)

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zfsdist(8) System Manager's Manual zfsdist(8)

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

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

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.

http://zfsonlinux.org

Since this uses BPF, only the root user can use this tool.

CONFIG_BPF and bcc.

Print usage message.
Don't include timestamps on interval output.
Output in milliseconds.
Trace this PID only.

# zfsdist
# zfsdist -p 181
# zfsdist 1 10
1 second summaries, printed in milliseconds
# zfsdist -m 1

Range of milliseconds for this bucket.
Range of microseconds for this bucket.
Number of operations in this time range.
ASCII representation of the distribution (the count column).

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.

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.

Linux

Unstable - in development.

Brendan Gregg

zfssnoop(8)

2016-02-12 USER COMMANDS