Manual: zfsdist-bpfcc

zfsdist(8)					   System Manager's Manual					  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  over‐
       head 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)

USER COMMANDS						 2016-02-12						  zfsdist(8)