| .TH mysqld_qslower 8 "2016-08-01" "USER COMMANDS" |
| .SH NAME |
| mysqld_qslower \- Trace MySQL server queries slower than a threshold. |
| .SH SYNOPSIS |
| .B mysqld_qslower PID [min_ms] |
| .SH 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. |
| .SH REQUIREMENTS |
| CONFIG_BPF, bcc, and MySQL server with USDT probe support (when configuring |
| the build: \-DENABLE_DTRACE=1). |
| .SH OPTIONS |
| PID |
| Trace this mysqld PID. |
| .TP |
| min_ms |
| Minimum query latency (duration) to trace, in milliseconds. Default is 1 ms. |
| .SH EXAMPLES |
| .TP |
| Trace MySQL server queries slower than 1 ms for PID 1981: |
| # |
| .B mysqld_qslower 1981 |
| .TP |
| Trace slower than 10 ms for PID 1981: |
| # |
| .B mysqld_qslower 1981 10 |
| .SH FIELDS |
| .TP |
| TIME(s) |
| Time of query start, in seconds. |
| .TP |
| PID |
| Process ID of the traced server. |
| .TP |
| MS |
| Milliseconds for the query, from start to end. |
| .TP |
| QUERY |
| Query string, truncated to 128 characters. |
| .SH 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. |
| .SH SOURCE |
| This is from bcc. |
| .IP |
| https://github.com/iovisor/bcc |
| .PP |
| Also look in the bcc distribution for a companion _examples.txt file containing |
| example usage, output, and commentary for this tool. |
| .SH OS |
| Linux |
| .SH STABILITY |
| Unstable - in development. |
| .SH AUTHOR |
| Brendan Gregg |
| .SH SEE ALSO |
| biosnoop(8) |
