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