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82 lines
2.1 KiB
82 lines
2.1 KiB
.TH btrfsdist 8 "2016-02-15" "USER COMMANDS" |
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.SH NAME |
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btrfsdist \- Summarize btrfs operation latency. Uses Linux eBPF/bcc. |
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.SH SYNOPSIS |
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.B btrfsdist [\-h] [\-T] [\-N] [\-d] [interval] [count] |
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.SH DESCRIPTION |
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This tool summarizes time (latency) spent in common btrfs file operations: |
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reads, writes, opens, and syncs, and presents it as a power-of-2 histogram. It |
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uses an in-kernel eBPF map to store the histogram for efficiency. |
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Since this works by tracing the btrfs_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 btrfs operation time, and print a summary on Ctrl-C: |
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# |
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.B btrfsdist |
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.TP |
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Trace PID 181 only: |
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# |
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.B btrfsdist -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 btrfsdist 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 btrfsdist \-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 btrfs writes and fsyncs, as well |
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as all system reads and opens (due to the current implementation of the |
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btrfs_file_operations interface). Particularly, all reads and writes from |
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the file system cache will incur extra overhead while tracing. Such reads and |
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writes 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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btrfsslower(8)
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