bcc-ext4dist(8)

1ext4dist(8)                 System Manager's Manual                ext4dist(8)
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NAME

6       ext4dist - Summarize ext4 operation latency. Uses Linux eBPF/bcc.
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SYNOPSIS

9       ext4dist [-h] [-T] [-m] [-p PID] [interval] [count]
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DESCRIPTION

12       This  tool  summarizes  time (latency) spent in common ext4 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       Since this works by tracing the  ext4_file_operations  interface  func‐
18       tions, it will need updating to match any changes to these functions.
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20       Since this uses BPF, only the root user can use this tool.
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REQUIREMENTS

23       CONFIG_BPF and bcc.
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OPTIONS

26       -h     Print usage message.
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28       -T     Don't include timestamps on interval output.
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30       -m     Output in milliseconds.
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32       -p PID Trace this PID only.
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EXAMPLES

35       Trace ext4 operation time, and print a summary on Ctrl-C:
36              # ext4dist
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38       Trace PID 181 only:
39              # ext4dist -p 181
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41       Print 1 second summaries, 10 times:
42              # ext4dist 1 10
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44       1 second summaries, printed in milliseconds
45              # ext4dist -m 1
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FIELDS

48       msecs  Range of milliseconds for this bucket.
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50       usecs  Range of microseconds for this bucket.
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52       count  Number of operations in this time range.
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54       distribution
55              ASCII representation of the distribution (the count column).
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OVERHEAD

58       This  adds  low-overhead  instrumentation  to  these  ext4  operations,
59       including reads and writes from the file system cache. Such  reads  and
60       writes can be very frequent (depending on the workload; eg, 1M/sec), at
61       which point the overhead of this tool may become  noticeable.   Measure
62       and quantify before use.
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SOURCE

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

73       Linux
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STABILITY

76       Unstable - in development.
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AUTHOR

79       Brendan Gregg
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