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gerrit-public.fairphone.software / platform / external / bcc / 19e337295d2f587a03a1d6524a954252e90b1f42 / . / tools / dbstat_example.txt
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Sasha Goldshtein24956982017-02-09 06:21:43 -0500[diff] [blame]1Demonstrations of dbstat, the Linux eBPF/bcc version.
2
3
4dbstat traces queries performed by a MySQL or PostgreSQL database process, and
5displays a histogram of query latencies. For example:
6
7# dbstat mysql
8Tracing database queries for pids 25776 slower than 0 ms...
9 query latency (ms) : count distribution
10 0 -> 1 : 990 |****************************************|
11 2 -> 3 : 7 | |
12 4 -> 7 : 0 | |
13 8 -> 15 : 0 | |
14 16 -> 31 : 0 | |
15 32 -> 63 : 0 | |
16 64 -> 127 : 0 | |
17 128 -> 255 : 0 | |
18 256 -> 511 : 0 | |
19 512 -> 1023 : 0 | |
20 1024 -> 2047 : 2 | |
21^C
22
23It's immediately evident that the vast majority of queries finish very quickly,
24in under 1ms, but there are some super-slow queries occasionally, in the 1-2
25seconds bucket.
26
27We can filter out the shorter queries with the -m switch:
28
29# dbstat mysql -m 1000
30Tracing database queries for pids 25776 slower than 1000 ms...
31 query latency (ms) : count distribution
32 0 -> 1 : 0 | |
33 2 -> 3 : 0 | |
34 4 -> 7 : 0 | |
35 8 -> 15 : 0 | |
36 16 -> 31 : 0 | |
37 32 -> 63 : 0 | |
38 64 -> 127 : 0 | |
39 128 -> 255 : 0 | |
40 256 -> 511 : 0 | |
41 512 -> 1023 : 0 | |
42 1024 -> 2047 : 8 |****************************************|
43^C
44
45By default, dbstat will try to detect mysqld and postgres processes, but if
46necessary, you can specify the process ids with the -p switch. Here, the -i
47switch is also used to request histograms at 3 second intervals:
48
49# dbstat mysql -p $(pidof mysql) -i 3
50Tracing database queries for pids 25776 slower than 0 ms...
51[06:14:36]
52 query latency (ms) : count distribution
53 0 -> 1 : 758 |****************************************|
54 2 -> 3 : 1 | |
55 4 -> 7 : 0 | |
56 8 -> 15 : 0 | |
57 16 -> 31 : 0 | |
58 32 -> 63 : 0 | |
59 64 -> 127 : 0 | |
60 128 -> 255 : 0 | |
61 256 -> 511 : 0 | |
62 512 -> 1023 : 0 | |
63 1024 -> 2047 : 1 | |
64
65[06:14:39]
66 query latency (ms) : count distribution
67 0 -> 1 : 436 |****************************************|
68 2 -> 3 : 2 | |
69 4 -> 7 : 0 | |
70 8 -> 15 : 0 | |
71 16 -> 31 : 0 | |
72 32 -> 63 : 0 | |
73 64 -> 127 : 0 | |
74 128 -> 255 : 0 | |
75 256 -> 511 : 0 | |
76 512 -> 1023 : 0 | |
77 1024 -> 2047 : 1 | |
78
79[06:14:42]
80 query latency (ms) : count distribution
81 0 -> 1 : 399 |****************************************|
82 2 -> 3 : 0 | |
83 4 -> 7 : 0 | |
84 8 -> 15 : 0 | |
85 16 -> 31 : 0 | |
86 32 -> 63 : 0 | |
87 64 -> 127 : 0 | |
88 128 -> 255 : 0 | |
89 256 -> 511 : 0 | |
90 512 -> 1023 : 0 | |
91 1024 -> 2047 : 1 | |
92^C
93
94
95USAGE:
96# dbstat -h
97usage: dbstat.py [-h] [-v] [-p [PID [PID ...]]] [-m THRESHOLD] [-u]
98 [-i INTERVAL]
99 {mysql,postgres}
100
101positional arguments:
102 {mysql,postgres} the database engine to use
103
104optional arguments:
105 -h, --help show this help message and exit
106 -v, --verbose print the BPF program
107 -p [PID [PID ...]], --pid [PID [PID ...]]
108 the pid(s) to trace
109 -m THRESHOLD, --threshold THRESHOLD
110 trace queries slower than this threshold (ms)
111 -u, --microseconds display query latencies in microseconds (default:
112 milliseconds)
113 -i INTERVAL, --interval INTERVAL
114 print summary at this interval (seconds)
115
116 dbstat postgres # display a histogram of PostgreSQL query latencies
117 dbstat mysql -v # display MySQL latencies and print the BPF program
118 dbstat mysql -u # display query latencies in microseconds (default: ms)
119 dbstat mysql -m 5 # trace only queries slower than 5ms
120 dbstat mysql -p 408 # trace queries in a specific process