mysqld_qslower

NAME

mysqld_qslower - Trace MySQL server queries slower than a threshold.

SYNOPSIS

mysqld_qslower PID [min_ms]

DESCRIPTION

This traces queries served by a MySQL server, and prints those that exceed a custom latency (query duration) threshold. By default, a minimum threshold of 1 millisecond is used. If a threshold of 0 is used, all queries are printed.

This uses User Statically-Defined Tracing (USDT) probes, a feature added to MySQL for DTrace support, but which may not be enabled on a given MySQL installation. See requirements.

Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

CONFIG_BPF, bcc, and MySQL server with USDT probe support (when configuring the build: -DENABLE_DTRACE=1).

OPTIONS

PID Trace this mysqld PID.
min_ms

Minimum query latency (duration) to trace, in milliseconds. Default is 1 ms.

EXAMPLES

Trace MySQL server queries slower than 1 ms for PID 1981:

# mysqld_qslower 1981

Trace slower than 10 ms for PID 1981:

# mysqld_qslower 1981 10

FIELDS

TIME(s)

Time of query start, in seconds.

	PID		Process ID of the traced server.
	MS		Milliseconds for the query, from start to end.
	QUERY		Query string, truncated to 128 characters.

OVERHEAD

This adds low-overhead instrumentation to MySQL queries, and only emits output data from kernel to user-level if they query exceeds the threshold. If the server query rate is less than 1,000/sec, the overhead is expected to be negligible. If the query rate is higher, test to gauge overhead.

SOURCE

This is from bcc.

https://github.com/iovisor/bcc

Also look in the bcc distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool.

OS

Linux

STABILITY

Unstable - in development.

AUTHOR

Brendan Gregg

SEE ALSO

biosnoop(8)