1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ================= 3 =================
4 Boot-time tracing 4 Boot-time tracing
5 ================= 5 =================
6 6
7 :Author: Masami Hiramatsu <mhiramat@kernel.org> 7 :Author: Masami Hiramatsu <mhiramat@kernel.org>
8 8
9 Overview 9 Overview
10 ======== 10 ========
11 11
12 Boot-time tracing allows users to trace boot-t 12 Boot-time tracing allows users to trace boot-time process including
13 device initialization with full features of ft 13 device initialization with full features of ftrace including per-event
14 filter and actions, histograms, kprobe-events 14 filter and actions, histograms, kprobe-events and synthetic-events,
15 and trace instances. 15 and trace instances.
16 Since kernel command line is not enough to con 16 Since kernel command line is not enough to control these complex features,
17 this uses bootconfig file to describe tracing 17 this uses bootconfig file to describe tracing feature programming.
18 18
19 Options in the Boot Config 19 Options in the Boot Config
20 ========================== 20 ==========================
21 21
22 Here is the list of available options list for 22 Here is the list of available options list for boot time tracing in
23 boot config file [1]_. All options are under " 23 boot config file [1]_. All options are under "ftrace." or "kernel."
24 prefix. See kernel parameters for the options 24 prefix. See kernel parameters for the options which starts
25 with "kernel." prefix [2]_. 25 with "kernel." prefix [2]_.
26 26
27 .. [1] See :ref:`Documentation/admin-guide/boo 27 .. [1] See :ref:`Documentation/admin-guide/bootconfig.rst <bootconfig>`
28 .. [2] See :ref:`Documentation/admin-guide/ker 28 .. [2] See :ref:`Documentation/admin-guide/kernel-parameters.rst <kernelparameters>`
29 29
30 Ftrace Global Options 30 Ftrace Global Options
31 --------------------- 31 ---------------------
32 32
33 Ftrace global options have "kernel." prefix in 33 Ftrace global options have "kernel." prefix in boot config, which means
34 these options are passed as a part of kernel l 34 these options are passed as a part of kernel legacy command line.
35 35
36 kernel.tp_printk 36 kernel.tp_printk
37 Output trace-event data on printk buffer to 37 Output trace-event data on printk buffer too.
38 38
39 kernel.dump_on_oops [= MODE] 39 kernel.dump_on_oops [= MODE]
40 Dump ftrace on Oops. If MODE = 1 or omitted 40 Dump ftrace on Oops. If MODE = 1 or omitted, dump trace buffer
41 on all CPUs. If MODE = 2, dump a buffer on 41 on all CPUs. If MODE = 2, dump a buffer on a CPU which kicks Oops.
42 42
43 kernel.traceoff_on_warning 43 kernel.traceoff_on_warning
44 Stop tracing if WARN_ON() occurs. 44 Stop tracing if WARN_ON() occurs.
45 45
46 kernel.fgraph_max_depth = MAX_DEPTH 46 kernel.fgraph_max_depth = MAX_DEPTH
47 Set MAX_DEPTH to maximum depth of fgraph tr 47 Set MAX_DEPTH to maximum depth of fgraph tracer.
48 48
49 kernel.fgraph_filters = FILTER[, FILTER2...] 49 kernel.fgraph_filters = FILTER[, FILTER2...]
50 Add fgraph tracing function filters. 50 Add fgraph tracing function filters.
51 51
52 kernel.fgraph_notraces = FILTER[, FILTER2...] 52 kernel.fgraph_notraces = FILTER[, FILTER2...]
53 Add fgraph non-tracing function filters. 53 Add fgraph non-tracing function filters.
54 54
55 55
56 Ftrace Per-instance Options 56 Ftrace Per-instance Options
57 --------------------------- 57 ---------------------------
58 58
59 These options can be used for each instance in 59 These options can be used for each instance including global ftrace node.
60 60
61 ftrace.[instance.INSTANCE.]options = OPT1[, OP 61 ftrace.[instance.INSTANCE.]options = OPT1[, OPT2[...]]
62 Enable given ftrace options. 62 Enable given ftrace options.
63 63
64 ftrace.[instance.INSTANCE.]tracing_on = 0|1 <<
65 Enable/Disable tracing on this instance whe <<
66 (you can enable it by the "traceon" event t <<
67 <<
68 ftrace.[instance.INSTANCE.]trace_clock = CLOCK 64 ftrace.[instance.INSTANCE.]trace_clock = CLOCK
69 Set given CLOCK to ftrace's trace_clock. 65 Set given CLOCK to ftrace's trace_clock.
70 66
71 ftrace.[instance.INSTANCE.]buffer_size = SIZE 67 ftrace.[instance.INSTANCE.]buffer_size = SIZE
72 Configure ftrace buffer size to SIZE. You c 68 Configure ftrace buffer size to SIZE. You can use "KB" or "MB"
73 for that SIZE. 69 for that SIZE.
74 70
75 ftrace.[instance.INSTANCE.]alloc_snapshot 71 ftrace.[instance.INSTANCE.]alloc_snapshot
76 Allocate snapshot buffer. 72 Allocate snapshot buffer.
77 73
78 ftrace.[instance.INSTANCE.]cpumask = CPUMASK 74 ftrace.[instance.INSTANCE.]cpumask = CPUMASK
79 Set CPUMASK as trace cpu-mask. 75 Set CPUMASK as trace cpu-mask.
80 76
81 ftrace.[instance.INSTANCE.]events = EVENT[, EV 77 ftrace.[instance.INSTANCE.]events = EVENT[, EVENT2[...]]
82 Enable given events on boot. You can use a 78 Enable given events on boot. You can use a wild card in EVENT.
83 79
84 ftrace.[instance.INSTANCE.]tracer = TRACER 80 ftrace.[instance.INSTANCE.]tracer = TRACER
85 Set TRACER to current tracer on boot. (e.g. 81 Set TRACER to current tracer on boot. (e.g. function)
86 82
87 ftrace.[instance.INSTANCE.]ftrace.filters 83 ftrace.[instance.INSTANCE.]ftrace.filters
88 This will take an array of tracing function 84 This will take an array of tracing function filter rules.
89 85
90 ftrace.[instance.INSTANCE.]ftrace.notraces 86 ftrace.[instance.INSTANCE.]ftrace.notraces
91 This will take an array of NON-tracing func 87 This will take an array of NON-tracing function filter rules.
92 88
93 89
94 Ftrace Per-Event Options 90 Ftrace Per-Event Options
95 ------------------------ 91 ------------------------
96 92
97 These options are setting per-event options. 93 These options are setting per-event options.
98 94
99 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.e 95 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.enable
100 Enable GROUP:EVENT tracing. 96 Enable GROUP:EVENT tracing.
101 97
102 ftrace.[instance.INSTANCE.]event.GROUP.enable <<
103 Enable all event tracing within GROUP. <<
104 <<
105 ftrace.[instance.INSTANCE.]event.enable <<
106 Enable all event tracing. <<
107 <<
108 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.f 98 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.filter = FILTER
109 Set FILTER rule to the GROUP:EVENT. 99 Set FILTER rule to the GROUP:EVENT.
110 100
111 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.a 101 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.actions = ACTION[, ACTION2[...]]
112 Set ACTIONs to the GROUP:EVENT. 102 Set ACTIONs to the GROUP:EVENT.
113 103
114 ftrace.[instance.INSTANCE.]event.kprobes.EVENT 104 ftrace.[instance.INSTANCE.]event.kprobes.EVENT.probes = PROBE[, PROBE2[...]]
115 Defines new kprobe event based on PROBEs. I 105 Defines new kprobe event based on PROBEs. It is able to define
116 multiple probes on one event, but those mus 106 multiple probes on one event, but those must have same type of
117 arguments. This option is available only fo 107 arguments. This option is available only for the event which
118 group name is "kprobes". 108 group name is "kprobes".
119 109
120 ftrace.[instance.INSTANCE.]event.synthetic.EVE 110 ftrace.[instance.INSTANCE.]event.synthetic.EVENT.fields = FIELD[, FIELD2[...]]
121 Defines new synthetic event with FIELDs. Ea 111 Defines new synthetic event with FIELDs. Each field should be
122 "type varname". 112 "type varname".
123 113
124 Note that kprobe and synthetic event definitio 114 Note that kprobe and synthetic event definitions can be written under
125 instance node, but those are also visible from 115 instance node, but those are also visible from other instances. So please
126 take care for event name conflict. 116 take care for event name conflict.
127 117
128 Ftrace Histogram Options <<
129 ------------------------ <<
130 <<
131 Since it is too long to write a histogram acti <<
132 action option, there are tree-style options un <<
133 for the histogram actions. For the detail of t <<
134 please read the event histogram document (Docu <<
135 <<
136 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
137 Set histogram key parameters. (Mandatory) <<
138 The 'N' is a digit string for the multiple h <<
139 if there is one histogram on the event. <<
140 <<
141 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
142 Set histogram value parameters. <<
143 <<
144 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
145 Set histogram sort parameter options. <<
146 <<
147 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
148 Set histogram size (number of entries). <<
149 <<
150 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
151 Set histogram name. <<
152 <<
153 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
154 Define a new VARIABLE by EXPR expression. <<
155 <<
156 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
157 Set histogram control parameter. You can set <<
158 <<
159 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
160 Set histogram 'onmatch' handler matching eve <<
161 The 'M' is a digit string for the multiple ' <<
162 if there is one 'onmatch' handler on this hi <<
163 <<
164 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
165 Set histogram 'trace' action for 'onmatch'. <<
166 EVENT must be a synthetic event name, and AR <<
167 for that event. Mandatory if 'onmatch.event' <<
168 <<
169 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
170 Set histogram 'onmax' handler variable param <<
171 <<
172 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
173 Set histogram 'onchange' handler variable pa <<
174 <<
175 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
176 Set histogram 'save' action parameters for ' <<
177 This option or below 'snapshot' option is ma <<
178 'onchange.var' option is set. <<
179 <<
180 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
181 Set histogram 'snapshot' action for 'onmax' <<
182 This option or above 'save' option is mandat <<
183 'onchange.var' option is set. <<
184 <<
185 ftrace.[instance.INSTANCE.]event.GROUP.EVENT.h <<
186 Set histogram filter expression. You don't n <<
187 <<
188 Note that this 'hist' option can conflict with <<
189 option if the 'actions' option has a histogram <<
190 <<
191 <<
192 When to Start <<
193 ============= <<
194 <<
195 All boot-time tracing options starting with `` <<
196 end of core_initcall. This means you can trace <<
197 Most of the subsystems and architecture depend <<
198 after that (arch_initcall or subsys_initcall). <<
199 boot-time tracing. <<
200 If you want to trace events before core_initca <<
201 starting with ``kernel``. Some of them will be <<
202 processing (for example,. ``kernel.ftrace=func <<
203 will start before the initcall.) <<
204 <<
205 118
206 Examples 119 Examples
207 ======== 120 ========
208 121
209 For example, to add filter and actions for eac 122 For example, to add filter and actions for each event, define kprobe
210 events, and synthetic events with histogram, w 123 events, and synthetic events with histogram, write a boot config like
211 below:: 124 below::
212 125
213 ftrace.event { 126 ftrace.event {
214 task.task_newtask { 127 task.task_newtask {
215 filter = "pid < 128" 128 filter = "pid < 128"
216 enable 129 enable
217 } 130 }
218 kprobes.vfs_read { 131 kprobes.vfs_read {
219 probes = "vfs_read $arg1 $arg2 132 probes = "vfs_read $arg1 $arg2"
220 filter = "common_pid < 200" 133 filter = "common_pid < 200"
221 enable 134 enable
222 } 135 }
223 synthetic.initcall_latency { 136 synthetic.initcall_latency {
224 fields = "unsigned long func", 137 fields = "unsigned long func", "u64 lat"
225 hist { !! 138 actions = "hist:keys=func.sym,lat:vals=lat:sort=lat"
226 keys = func.sym, lat !! 139 }
227 values = lat !! 140 initcall.initcall_start {
228 sort = lat !! 141 actions = "hist:keys=func:ts0=common_timestamp.usecs"
229 } !! 142 }
230 } !! 143 initcall.initcall_finish {
231 initcall.initcall_start.hist { !! 144 actions = "hist:keys=func:lat=common_timestamp.usecs-$ts0:onmatch(initcall.initcall_start).initcall_latency(func,$lat)"
232 keys = func <<
233 var.ts0 = common_timestamp.use <<
234 } <<
235 initcall.initcall_finish.hist { <<
236 keys = func <<
237 var.lat = common_timestamp.use <<
238 onmatch { <<
239 event = initcall.initc <<
240 trace = initcall_laten <<
241 } <<
242 } 145 }
243 } 146 }
244 147
245 Also, boot-time tracing supports "instance" no 148 Also, boot-time tracing supports "instance" node, which allows us to run
246 several tracers for different purpose at once. 149 several tracers for different purpose at once. For example, one tracer
247 is for tracing functions starting with "user\_ 150 is for tracing functions starting with "user\_", and others tracing
248 "kernel\_" functions, you can write boot confi 151 "kernel\_" functions, you can write boot config as below::
249 152
250 ftrace.instance { 153 ftrace.instance {
251 foo { 154 foo {
252 tracer = "function" 155 tracer = "function"
253 ftrace.filters = "user_*" 156 ftrace.filters = "user_*"
254 } 157 }
255 bar { 158 bar {
256 tracer = "function" 159 tracer = "function"
257 ftrace.filters = "kernel_*" 160 ftrace.filters = "kernel_*"
258 } 161 }
259 } 162 }
260 163
261 The instance node also accepts event nodes so 164 The instance node also accepts event nodes so that each instance
262 can customize its event tracing. 165 can customize its event tracing.
263 <<
264 With the trigger action and kprobes, you can t <<
265 a function is called. For example, this will t <<
266 the pci_proc_init():: <<
267 <<
268 ftrace { <<
269 tracing_on = 0 <<
270 tracer = function_graph <<
271 event.kprobes { <<
272 start_event { <<
273 probes = "pci_proc_ini <<
274 actions = "traceon" <<
275 } <<
276 end_event { <<
277 probes = "pci_proc_ini <<
278 actions = "traceoff" <<
279 } <<
280 } <<
281 } <<
282 <<
283 166
284 This boot-time tracing also supports ftrace ke 167 This boot-time tracing also supports ftrace kernel parameters via boot
285 config. 168 config.
286 For example, following kernel parameters:: 169 For example, following kernel parameters::
287 170
288 trace_options=sym-addr trace_event=initcall:* 171 trace_options=sym-addr trace_event=initcall:* tp_printk trace_buf_size=1M ftrace=function ftrace_filter="vfs*"
289 172
290 This can be written in boot config like below: 173 This can be written in boot config like below::
291 174
292 kernel { 175 kernel {
293 trace_options = sym-addr 176 trace_options = sym-addr
294 trace_event = "initcall:*" 177 trace_event = "initcall:*"
295 tp_printk 178 tp_printk
296 trace_buf_size = 1M 179 trace_buf_size = 1M
297 ftrace = function 180 ftrace = function
298 ftrace_filter = "vfs*" 181 ftrace_filter = "vfs*"
299 } 182 }
300 183
301 Note that parameters start with "kernel" prefi 184 Note that parameters start with "kernel" prefix instead of "ftrace".
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