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54 lines
1.4 KiB
54 lines
1.4 KiB
7 months ago
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.TH syncsnoop 8 "2015-08-18" "USER COMMANDS"
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.SH NAME
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syncsnoop \- Trace sync() syscall. Uses Linux eBPF/bcc.
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.SH SYNOPSIS
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.B syncsnoop
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.SH DESCRIPTION
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syncsnoop traces calls to sync(), which flushes file system buffers to
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storage devices. These calls can cause performance perturbations, and it can
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be useful to know if they are happening and how frequently.
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This works by tracing the kernel sys_sync() function using dynamic tracing, and
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will need updating to match any changes to this function.
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This makes use of a Linux 4.5 feature (bpf_perf_event_output());
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for kernels older than 4.5, see the version under tools/old,
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which uses an older mechanism.
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This program is also a basic example of eBPF/bcc.
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Since this uses BPF, only the root user can use this tool.
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.SH REQUIREMENTS
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CONFIG_BPF and bcc.
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.SH EXAMPLES
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.TP
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Trace calls to sync():
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#
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.B syncsnoop
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.SH FIELDS
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.TP
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TIME(s)
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Time of the call, in seconds.
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.TP
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CALL
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Call traced.
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.SH OVERHEAD
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This traces the kernel sync function and prints output for each event. As the
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rate of this is generally expected to be low (<< 100/s), the overhead is also
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expected to be negligible.
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.SH SOURCE
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This is from bcc.
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.IP
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https://github.com/iovisor/bcc
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.PP
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Also look in the bcc distribution for a companion _examples.txt file containing
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example usage, output, and commentary for this tool.
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.SH OS
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Linux
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.SH STABILITY
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Unstable - in development.
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.SH AUTHOR
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Brendan Gregg
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.SH SEE ALSO
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iostat(1)
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