bcc-zfsdist(8)

1zfsdist(8)                  System Manager's Manual                 zfsdist(8)
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NAME

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

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

12       This  tool  summarizes  time  (latency) spent in common ZFS file opera‐
13       tions: reads, writes, opens, and syncs, and presents it as a power-of-2
14       histogram.  It  uses  an  in-kernel eBPF map to store the histogram for
15       efficiency.
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17       This uses kernel dynamic  tracing  of  the  ZPL  interface  (ZFS  POSIX
18       Layer), and will need updates to match any changes to this interface.
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20       This is intended to work with the ZFS on Linux project:
21              http://zfsonlinux.org
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23       Since this uses BPF, only the root user can use this tool.
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REQUIREMENTS

26       CONFIG_BPF and bcc.
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OPTIONS

29       -h     Print usage message.
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31       -T     Don't include timestamps on interval output.
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33       -m     Output in milliseconds.
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35       -p PID Trace this PID only.
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EXAMPLES

38       Trace ZFS operation time, and print a summary on Ctrl-C:
39              # zfsdist
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41       Trace PID 181 only:
42              # zfsdist -p 181
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44       Print 1 second summaries, 10 times:
45              # zfsdist 1 10
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47       1 second summaries, printed in milliseconds
48              # zfsdist -m 1
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FIELDS

51       msecs  Range of milliseconds for this bucket.
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53       usecs  Range of microseconds for this bucket.
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55       count  Number of operations in this time range.
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57       distribution
58              ASCII representation of the distribution (the count column).
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OVERHEAD

61       This adds low-overhead instrumentation to these ZFS operations, includ‐
62       ing reads and writes from the file system cache. Such reads and  writes
63       can  be very frequent (depending on the workload; eg, 1M/sec), at which
64       point the overhead of this tool may  become  noticeable.   Measure  and
65       quantify before use.
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SOURCE

68       This is from bcc.
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70              https://github.com/iovisor/bcc
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72       Also  look  in  the bcc distribution for a companion _examples.txt file
73       containing example usage, output, and commentary for this tool.
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OS

76       Linux
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STABILITY

79       Unstable - in development.
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AUTHOR

82       Brendan Gregg
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