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67 lines
1.9 KiB
67 lines
1.9 KiB
.TH mysqld_qslower 8 "2016-08-01" "USER COMMANDS"
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.SH NAME
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mysqld_qslower \- Trace MySQL server queries slower than a threshold.
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.SH SYNOPSIS
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.B mysqld_qslower PID [min_ms]
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.SH DESCRIPTION
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This traces queries served by a MySQL server, and prints those that exceed a
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custom latency (query duration) threshold. By default, a minimum threshold of 1
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millisecond is used. If a threshold of 0 is used, all queries are printed.
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This uses User Statically-Defined Tracing (USDT) probes, a feature added to
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MySQL for DTrace support, but which may not be enabled on a given MySQL
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installation. See requirements.
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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, bcc, and MySQL server with USDT probe support (when configuring
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the build: \-DENABLE_DTRACE=1).
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.SH OPTIONS
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PID
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Trace this mysqld PID.
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.TP
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min_ms
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Minimum query latency (duration) to trace, in milliseconds. Default is 1 ms.
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.SH EXAMPLES
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.TP
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Trace MySQL server queries slower than 1 ms for PID 1981:
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#
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.B mysqld_qslower 1981
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.TP
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Trace slower than 10 ms for PID 1981:
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#
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.B mysqld_qslower 1981 10
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.SH FIELDS
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.TP
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TIME(s)
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Time of query start, in seconds.
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.TP
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PID
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Process ID of the traced server.
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.TP
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MS
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Milliseconds for the query, from start to end.
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.TP
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QUERY
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Query string, truncated to 128 characters.
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.SH OVERHEAD
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This adds low-overhead instrumentation to MySQL queries, and only emits output
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data from kernel to user-level if they query exceeds the threshold. If the
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server query rate is less than 1,000/sec, the overhead is expected to be
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negligible. If the query rate is higher, test to gauge overhead.
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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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biosnoop(8)
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