1 Demonstrations of mysqld_qslower, the Linux eBPF/bcc version. 2 3 4 mysqld_qslower traces queries served by a MySQL server, and prints those that 5 exceed a latency (query time) threshold. By default a threshold of 1 ms is 6 used. For example: 7 8 # ./mysqld_qslower.py `pgrep -n mysqld` 9 Tracing MySQL server queries for PID 14371 slower than 1 ms... 10 TIME(s) PID MS QUERY 11 0.000000 18608 130.751 SELECT * FROM words WHERE word REGEXP '^bre.*n$' 12 2.921535 18608 130.590 SELECT * FROM words WHERE word REGEXP '^alex.*$' 13 4.603549 18608 24.164 SELECT COUNT(*) FROM words 14 9.733847 18608 130.936 SELECT count(*) AS count FROM words WHERE word REGEXP '^bre.*n$' 15 17.864776 18608 130.298 SELECT * FROM words WHERE word REGEXP '^bre.*n$' ORDER BY word 16 17 This traced 5 queries, 4 of which took about 130 milliseconds. 18 19 A pgrep command was used to specify the PID of mysqld. 20 21 22 In this example, a lower threshold is used of 0.1 ms: 23 24 # ./mysqld_qslower.py `pgrep -n mysqld` 0.1 25 Tracing MySQL server queries for PID 14371 slower than 0.1 ms... 26 TIME(s) PID MS QUERY 27 0.000000 18608 24.201 SELECT COUNT(*) FROM words 28 13.242390 18608 130.378 SELECT * FROM words WHERE word REGEXP '^bre.*n$' 29 23.601751 18608 119.198 SELECT * FROM words WHERE word REGEXP '^zzzzzzzz$' 30 31 It worked, but I'm not catching any faster queries in this example. Notice I 32 added a query that searched for "zzzzzzzz": it returned an empty set, and ran 33 11 ms faster. 34 35 36 A 0 ms threshold can be specified to trace all queries: 37 38 # ./mysqld_qslower.py `pgrep -n mysqld` 0 39 Tracing MySQL server queries for PID 14371 slower than 0 ms... 40 TIME(s) PID MS QUERY 41 0.000000 18608 0.105 select @@version_comment limit 1 42 2.049312 18608 0.099 SELECT DATABASE() 43 2.050666 18608 0.274 show databases 44 2.051040 18608 0.176 show tables 45 5.730044 18608 130.365 SELECT count(*) AS count FROM words WHERE word REGEXP '^bre.*n$' 46 9.273837 18608 0.096 select 1 47 9.553742 18608 0.059 select 1 48 9.986087 18608 0.080 select 1 49 50 This includes an initialization of a mysql client command, and selecting the 51 database. I also added some "select 1;" queries, which do no work and return 52 quickly. 53 54 55 USAGE: 56 57 # ./mysqld_qslower.py -h 58 USAGE: mysqld_latency PID [min_ms] 59
