forked from iovisor/bcc
-
Notifications
You must be signed in to change notification settings - Fork 4
/
vfsreadlat_example.txt
63 lines (55 loc) · 3.53 KB
/
vfsreadlat_example.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
Demonstrations of vfsreadlat.py, the Linux eBPF/bcc version.
This example traces the latency of vfs_read (time from call to return), printing
it as a histogram distribution. By default, output is every five seconds:
# ./vfsreadlat.py
Tracing... Hit Ctrl-C to end.
usecs : count distribution
0 -> 1 : 4457 |*************************************+|
2 -> 3 : 447 |*** |
4 -> 7 : 2059 |***************** |
8 -> 15 : 1179 |********** |
16 -> 31 : 63 | |
32 -> 63 : 0 | |
64 -> 127 : 2 | |
128 -> 255 : 0 | |
256 -> 511 : 3 | |
512 -> 1023 : 1 | |
1024 -> 2047 : 3 | |
2048 -> 4095 : 2 | |
4096 -> 8191 : 0 | |
8192 -> 16383 : 0 | |
16384 -> 32767 : 0 | |
32768 -> 65535 : 0 | |
65536 -> 131071 : 4 | |
131072 -> 262143 : 2 | |
262144 -> 524287 : 0 | |
524288 -> 1048575 : 4 | |
^C
usecs : count distribution
0 -> 1 : 241 |*************************************+|
2 -> 3 : 17 |** |
4 -> 7 : 2 | |
8 -> 15 : 4 | |
16 -> 31 : 2 | |
32 -> 63 : 0 | |
64 -> 127 : 1 | |
128 -> 255 : 0 | |
256 -> 511 : 1 | |
512 -> 1023 : 1 | |
1024 -> 2047 : 0 | |
2048 -> 4095 : 1 | |
4096 -> 8191 : 0 | |
8192 -> 16383 : 0 | |
16384 -> 32767 : 0 | |
32768 -> 65535 : 0 | |
65536 -> 131071 : 0 | |
131072 -> 262143 : 0 | |
262144 -> 524287 : 0 | |
524288 -> 1048575 : 1 | |
These examples show outliers in the 524 - 1048 milliseconds range. Since
vfs_read() will catch many types of events, this could be anything including
keystroke latency on ssh sessions. Further drilling with bcc will be necessary
to identify more details.
Full usage:
# ./vfsreadlat.py -h
USAGE: ./vfsreadlat.py [interval [count]]