1zfsdist(8)                  System Manager's Manual                 zfsdist(8)
2
3
4

NAME

6       zfsdist - Summarize ZFS operation latency. Uses Linux eBPF/bcc.
7

SYNOPSIS

9       zfsdist [-h] [-T] [-m] [-p PID] [interval] [count]
10

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.
16
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.
19
20       This is intended to work with the ZFS on Linux project:
21              http://zfsonlinux.org
22
23       Since this uses BPF, only the root user can use this tool.
24

REQUIREMENTS

26       CONFIG_BPF and bcc.
27

OPTIONS

29       -h     Print usage message.
30
31       -T     Don't include timestamps on interval output.
32
33       -m     Output in milliseconds.
34
35       -p PID Trace this PID only.
36

EXAMPLES

38       Trace ZFS operation time, and print a summary on Ctrl-C:
39              # zfsdist
40
41       Trace PID 181 only:
42              # zfsdist -p 181
43
44       Print 1 second summaries, 10 times:
45              # zfsdist 1 10
46
47       1 second summaries, printed in milliseconds
48              # zfsdist -m 1
49

FIELDS

51       msecs  Range of milliseconds for this bucket.
52
53       usecs  Range of microseconds for this bucket.
54
55       count  Number of operations in this time range.
56
57       distribution
58              ASCII representation of the distribution (the count column).
59

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.
66

SOURCE

68       This is from bcc.
69
70              https://github.com/iovisor/bcc
71
72       Also  look  in  the bcc distribution for a companion _examples.txt file
73       containing example usage, output, and commentary for this tool.
74

OS

76       Linux
77

STABILITY

79       Unstable - in development.
80

AUTHOR

82       Brendan Gregg
83

SEE ALSO

85       zfssnoop(8)
86
87
88
89USER COMMANDS                     2016-02-12                        zfsdist(8)
Impressum