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81 lines
1.9 KiB
81 lines
1.9 KiB
.TH xfsdist 8 "2016-02-12" "USER COMMANDS"
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.SH NAME
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xfsdist \- Summarize XFS operation latency. Uses Linux eBPF/bcc.
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.SH SYNOPSIS
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.B xfsdist [\-h] [\-T] [\-m] [\-p PID] [interval] [count]
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.SH DESCRIPTION
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This tool summarizes time (latency) spent in common XFS file operations: reads,
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writes, opens, and syncs, and presents it as a power-of-2 histogram. It uses an
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in-kernel eBPF map to store the histogram for efficiency.
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Since this works by tracing the xfs_file_operations interface functions, it
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will need updating to match any changes to these functions.
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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 OPTIONS
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.TP
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\-h
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Print usage message.
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.TP
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\-T
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Don't include timestamps on interval output.
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.TP
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\-m
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Output in milliseconds.
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.TP
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\-p PID
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Trace this PID only.
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.SH EXAMPLES
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.TP
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Trace XFS operation time, and print a summary on Ctrl-C:
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#
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.B xfsdist
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.TP
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Trace PID 181 only:
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#
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.B xfsdist -p 181
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.TP
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Print 1 second summaries, 10 times:
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#
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.B xfsdist 1 10
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.TP
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1 second summaries, printed in milliseconds
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#
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.B xfsdist \-m 1
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.SH FIELDS
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.TP
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msecs
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Range of milliseconds for this bucket.
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.TP
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usecs
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Range of microseconds for this bucket.
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.TP
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count
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Number of operations in this time range.
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.TP
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distribution
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ASCII representation of the distribution (the count column).
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.SH OVERHEAD
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This adds low-overhead instrumentation to these XFS operations,
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including reads and writes from the file system cache. Such reads and writes
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can be very frequent (depending on the workload; eg, 1M/sec), at which
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point the overhead of this tool may become noticeable.
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Measure and quantify before use.
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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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xfssnoop(8)
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