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
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
|
Demonstrations of softirqs, the Linux eBPF/bcc version.
This program traces soft interrupts (irqs), and stores timing statistics
in-kernel for efficiency. For example:
# ./softirqs
Tracing soft irq event time... Hit Ctrl-C to end.
^C
SOFTIRQ TOTAL_usecs
rcu_process_callbacks 974
run_rebalance_domains 1809
run_timer_softirq 2615
net_tx_action 14605
tasklet_action 38692
net_rx_action 88188
The SOFTIRQ column prints the interrupt action function name. While tracing,
the net_rx_action() soft interrupt ran for 20199 microseconds (20 milliseconds)
in total.
This tool works by dynamic tracing the individual softirq functions, and will
need to be adjusted to match kernel/module changes. Future versions should
use the softirq tracepoints instead.
An interval can be provided, and also optionally a count. Eg, printing output
every 1 second, and including timestamps (-T):
# ./softirqs -T 1 3
Tracing soft irq event time... Hit Ctrl-C to end.
22:29:16
SOFTIRQ TOTAL_usecs
rcu_process_callbacks 456
run_rebalance_domains 1005
run_timer_softirq 1196
net_tx_action 2796
tasklet_action 5534
net_rx_action 15075
22:29:17
SOFTIRQ TOTAL_usecs
rcu_process_callbacks 456
run_rebalance_domains 839
run_timer_softirq 1142
net_tx_action 1912
tasklet_action 4428
net_rx_action 14652
22:29:18
SOFTIRQ TOTAL_usecs
rcu_process_callbacks 502
run_rebalance_domains 840
run_timer_softirq 1192
net_tx_action 2341
tasklet_action 5496
net_rx_action 15656
This can be useful for quantifying where CPU cycles are spent among the soft
interrupts (summarized as the %softirq column from mpstat(1), and shown as
event counts in /proc/softirqs). The output above shows that most time was spent
processing net_rx_action(), which was around 15 milliseconds per second (total
time across all CPUs).
The distribution of interrupt run time can be printed as a histogram with the -d
option. Eg:
# ./softirqs -d
Tracing soft irq event time... Hit Ctrl-C to end.
^C
softirq = net_tx_action
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 440 | |
512 -> 1023 : 27613 |****************************************|
1024 -> 2047 : 5728 |******** |
2048 -> 4095 : 439 | |
4096 -> 8191 : 53 | |
8192 -> 16383 : 2 | |
softirq = net_rx_action
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 6 | |
1024 -> 2047 : 35 | |
2048 -> 4095 : 3562 |**************** |
4096 -> 8191 : 7023 |******************************** |
8192 -> 16383 : 8770 |****************************************|
16384 -> 32767 : 1780 |******** |
32768 -> 65535 : 216 | |
65536 -> 131071 : 4 | |
softirq = tasklet_action
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 95 | |
512 -> 1023 : 12521 |****************************************|
1024 -> 2047 : 1068 |*** |
2048 -> 4095 : 1077 |*** |
4096 -> 8191 : 12349 |*************************************** |
8192 -> 16383 : 464 |* |
16384 -> 32767 : 1 | |
softirq = rcu_process_callbacks
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 0 | |
512 -> 1023 : 708 |****************************************|
1024 -> 2047 : 495 |*************************** |
2048 -> 4095 : 98 |***** |
4096 -> 8191 : 62 |*** |
8192 -> 16383 : 4 | |
softirq = run_timer_softirq
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 2 | |
512 -> 1023 : 366 |********* |
1024 -> 2047 : 1525 |****************************************|
2048 -> 4095 : 629 |**************** |
4096 -> 8191 : 87 |** |
8192 -> 16383 : 1 | |
softirq = run_rebalance_domains
usecs : count distribution
0 -> 1 : 0 | |
2 -> 3 : 0 | |
4 -> 7 : 0 | |
8 -> 15 : 0 | |
16 -> 31 : 0 | |
32 -> 63 : 0 | |
64 -> 127 : 0 | |
128 -> 255 : 0 | |
256 -> 511 : 3 | |
512 -> 1023 : 18 |* |
1024 -> 2047 : 80 |******** |
2048 -> 4095 : 374 |****************************************|
4096 -> 8191 : 257 |*************************** |
8192 -> 16383 : 50 |***** |
16384 -> 32767 : 24 |** |
Sometimes you just want counts of events, and don't need the distribution
of times. You can use the -C or --events option:
# ./softirqs.py -C
Tracing soft irq events... Hit Ctrl-C to end.
^C
SOFTIRQ TOTAL_count
block 5
tasklet 6
net_rx 402
sched 5251
rcu 5748
timer 9530
USAGE message:
# ./softirqs -h
usage: softirqs [-h] [-T] [-N] [-C] [-d] [-c CPU] [interval] [count]
Summarize soft irq event time as histograms.
positional arguments:
interval output interval, in seconds
count number of outputs
optional arguments:
-h, --help show this help message and exit
-T, --timestamp include timestamp on output
-N, --nanoseconds output in nanoseconds
-C, --events show the number of soft irq events
-d, --dist show distributions as histograms
-c CPU, --cpu CPU trace this CPU only
examples:
./softirqs # sum soft irq event time
./softirqs -C # show the number of soft irq events
./softirqs -d # show soft irq event time as histograms
./softirqs 1 10 # print 1 second summaries, 10 times
./softirqs -NT 1 # 1s summaries, nanoseconds, and timestamps
./softirqs -c 1 # sum soft irq event time on CPU 1 only
|
