biosnoop(8)

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

6       biosnoop.bt  -  Block  I/O  tracing tool, showing per I/O latency. Uses
7       bpftrace/eBPF.
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SYNOPSIS

10       biosnoop.bt
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DESCRIPTION

13       This is a basic block I/O (disk I/O) tracing  tool,  showing  each  I/O
14       event  along with the issuing process ID, and the I/O latency. This can
15       be used to investigate disk I/O performance issues.
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17       This tool currently works by dynamic tracing of the blk_account*() ker‐
18       nel  functions,  which will need updating to match any changes to these
19       functions in future kernels versions.
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21       Since this uses BPF, only the root user can use this tool.
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REQUIREMENTS

24       CONFIG_BPF and bpftrace.
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EXAMPLES

27       Trace block I/O events, printing per-line summaries:
28              # biosnoop.bt
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FIELDS

31       TIME   Time of the I/O completion, in milliseconds since program start.
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33       COMM   Issuing process name. This often identifies the issuing applica‐
34              tion process, but I/O may be initiated from kernel threads only.
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36       PID    Issuing  process  ID. This often identifies the issuing applica‐
37              tion process, but I/O may be initiated from kernel threads only.
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39       ARGS   Process name and arguments (16 word maximum).
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OVERHEAD

42       Since block device I/O  usually  has  a  relatively  low  frequency  (<
43       10,000/s), the overhead for this tool is expected to be negligible. For
44       high IOPS storage systems, test and quantify before use.
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SOURCE

47       This is from bpftrace.
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49              https://github.com/iovisor/bpftrace
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51       Also look in the bpftrace distribution for  a  companion  _examples.txt
52       file containing example usage, output, and commentary for this tool.
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54       This  is  a  bpftrace version of the bcc tool of the same name. The bcc
55       tool provides more fields.
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57              https://github.com/iovisor/bcc
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OS

60       Linux
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STABILITY

63       Unstable - in development.
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AUTHOR

66       Brendan Gregg
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