bcc-syncsnoop(8)

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

6       syncsnoop - Trace sync() syscall. Uses Linux eBPF/bcc.
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SYNOPSIS

9       syncsnoop
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DESCRIPTION

12       syncsnoop  traces calls to sync(), which flushes file system buffers to
13       storage devices. These calls can cause performance  perturbations,  and
14       it can be useful to know if they are happening and how frequently.
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16       This  works  by  tracing  the  kernel sys_sync() function using dynamic
17       tracing, and will need updating to match any changes to this function.
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19       This makes use of a Linux 4.5  feature  (bpf_perf_event_output());  for
20       kernels  older than 4.5, see the version under tools/old, which uses an
21       older mechanism.
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23       This program is also a basic example of eBPF/bcc.
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25       Since this uses BPF, only the root user can use this tool.
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REQUIREMENTS

28       CONFIG_BPF and bcc.
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EXAMPLES

31       Trace calls to sync():
32              # syncsnoop
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FIELDS

35       TIME(s)
36              Time of the call, in seconds.
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38       CALL   Call traced.
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OVERHEAD

41       This traces the kernel sync function and prints output for each  event.
42       As  the  rate  of  this is generally expected to be low (<< 100/s), the
43       overhead is also expected to be negligible.
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SOURCE

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

54       Linux
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STABILITY

57       Unstable - in development.
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AUTHOR

60       Brendan Gregg
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