1 # SPDX-License-Identifier: GPL-2.0-only 1 # SPDX-License-Identifier: GPL-2.0-only
2 # 2 #
3 # Architectures that offer an FUNCTION_TRACER 3 # Architectures that offer an FUNCTION_TRACER implementation should
4 # select HAVE_FUNCTION_TRACER: 4 # select HAVE_FUNCTION_TRACER:
5 # 5 #
6 6
7 config USER_STACKTRACE_SUPPORT 7 config USER_STACKTRACE_SUPPORT
8 bool 8 bool
9 9
10 config NOP_TRACER 10 config NOP_TRACER
11 bool 11 bool
12 12
13 config HAVE_RETHOOK 13 config HAVE_RETHOOK
14 bool 14 bool
15 15
16 config RETHOOK 16 config RETHOOK
17 bool 17 bool
18 depends on HAVE_RETHOOK 18 depends on HAVE_RETHOOK
19 help 19 help
20 Enable generic return hooking featur 20 Enable generic return hooking feature. This is an internal
21 API, which will be used by other fun 21 API, which will be used by other function-entry hooking
22 features like fprobe and kprobes. 22 features like fprobe and kprobes.
23 23
24 config HAVE_FUNCTION_TRACER 24 config HAVE_FUNCTION_TRACER
25 bool 25 bool
26 help 26 help
27 See Documentation/trace/ftrace-desig 27 See Documentation/trace/ftrace-design.rst
28 28
29 config HAVE_FUNCTION_GRAPH_TRACER 29 config HAVE_FUNCTION_GRAPH_TRACER
30 bool 30 bool
31 help 31 help
32 See Documentation/trace/ftrace-desig 32 See Documentation/trace/ftrace-design.rst
33 33
34 config HAVE_FUNCTION_GRAPH_RETVAL <<
35 bool <<
36 <<
37 config HAVE_DYNAMIC_FTRACE 34 config HAVE_DYNAMIC_FTRACE
38 bool 35 bool
39 help 36 help
40 See Documentation/trace/ftrace-desig 37 See Documentation/trace/ftrace-design.rst
41 38
42 config HAVE_DYNAMIC_FTRACE_WITH_REGS 39 config HAVE_DYNAMIC_FTRACE_WITH_REGS
43 bool 40 bool
44 41
45 config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS 42 config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
46 bool 43 bool
47 44
48 config HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS 45 config HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
49 bool 46 bool
50 47
51 config HAVE_DYNAMIC_FTRACE_WITH_ARGS 48 config HAVE_DYNAMIC_FTRACE_WITH_ARGS
52 bool 49 bool
53 help 50 help
54 If this is set, then arguments and st 51 If this is set, then arguments and stack can be found from
55 the ftrace_regs passed into the funct 52 the ftrace_regs passed into the function callback regs parameter
56 by default, even without setting the 53 by default, even without setting the REGS flag in the ftrace_ops.
57 This allows for use of ftrace_regs_ge 54 This allows for use of ftrace_regs_get_argument() and
58 ftrace_regs_get_stack_pointer(). 55 ftrace_regs_get_stack_pointer().
59 56
60 config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE 57 config HAVE_DYNAMIC_FTRACE_NO_PATCHABLE
61 bool 58 bool
62 help 59 help
63 If the architecture generates __patc 60 If the architecture generates __patchable_function_entries sections
64 but does not want them included in t 61 but does not want them included in the ftrace locations.
65 62
66 config HAVE_FTRACE_MCOUNT_RECORD 63 config HAVE_FTRACE_MCOUNT_RECORD
67 bool 64 bool
68 help 65 help
69 See Documentation/trace/ftrace-desig 66 See Documentation/trace/ftrace-design.rst
70 67
71 config HAVE_SYSCALL_TRACEPOINTS 68 config HAVE_SYSCALL_TRACEPOINTS
72 bool 69 bool
73 help 70 help
74 See Documentation/trace/ftrace-desig 71 See Documentation/trace/ftrace-design.rst
75 72
76 config HAVE_FENTRY 73 config HAVE_FENTRY
77 bool 74 bool
78 help 75 help
79 Arch supports the gcc options -pg wi 76 Arch supports the gcc options -pg with -mfentry
80 77
81 config HAVE_NOP_MCOUNT 78 config HAVE_NOP_MCOUNT
82 bool 79 bool
83 help 80 help
84 Arch supports the gcc options -pg wi 81 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
85 82
86 config HAVE_OBJTOOL_MCOUNT 83 config HAVE_OBJTOOL_MCOUNT
87 bool 84 bool
88 help 85 help
89 Arch supports objtool --mcount 86 Arch supports objtool --mcount
90 87
91 config HAVE_OBJTOOL_NOP_MCOUNT 88 config HAVE_OBJTOOL_NOP_MCOUNT
92 bool 89 bool
93 help 90 help
94 Arch supports the objtool options -- 91 Arch supports the objtool options --mcount with --mnop.
95 An architecture can select this if i 92 An architecture can select this if it wants to enable nop'ing
96 of ftrace locations. 93 of ftrace locations.
97 94
98 config HAVE_C_RECORDMCOUNT 95 config HAVE_C_RECORDMCOUNT
99 bool 96 bool
100 help 97 help
101 C version of recordmcount available? 98 C version of recordmcount available?
102 99
103 config HAVE_BUILDTIME_MCOUNT_SORT 100 config HAVE_BUILDTIME_MCOUNT_SORT
104 bool 101 bool
105 help 102 help
106 An architecture selects this if it so 103 An architecture selects this if it sorts the mcount_loc section
107 at build time. 104 at build time.
108 105
109 config BUILDTIME_MCOUNT_SORT 106 config BUILDTIME_MCOUNT_SORT
110 bool 107 bool
111 default y 108 default y
112 depends on HAVE_BUILDTIME_MCOUNT_SORT & 109 depends on HAVE_BUILDTIME_MCOUNT_SORT && DYNAMIC_FTRACE
113 help 110 help
114 Sort the mcount_loc section at build 111 Sort the mcount_loc section at build time.
115 112
116 config TRACER_MAX_TRACE 113 config TRACER_MAX_TRACE
117 bool 114 bool
118 115
119 config TRACE_CLOCK 116 config TRACE_CLOCK
120 bool 117 bool
121 118
122 config RING_BUFFER 119 config RING_BUFFER
123 bool 120 bool
124 select TRACE_CLOCK 121 select TRACE_CLOCK
125 select IRQ_WORK 122 select IRQ_WORK
126 123
127 config EVENT_TRACING 124 config EVENT_TRACING
128 select CONTEXT_SWITCH_TRACER 125 select CONTEXT_SWITCH_TRACER
129 select GLOB 126 select GLOB
130 bool 127 bool
131 128
132 config CONTEXT_SWITCH_TRACER 129 config CONTEXT_SWITCH_TRACER
133 bool 130 bool
134 131
135 config RING_BUFFER_ALLOW_SWAP 132 config RING_BUFFER_ALLOW_SWAP
136 bool 133 bool
137 help 134 help
138 Allow the use of ring_buffer_swap_cpu 135 Allow the use of ring_buffer_swap_cpu.
139 Adds a very slight overhead to tracin 136 Adds a very slight overhead to tracing when enabled.
140 137
141 config PREEMPTIRQ_TRACEPOINTS 138 config PREEMPTIRQ_TRACEPOINTS
142 bool 139 bool
143 depends on TRACE_PREEMPT_TOGGLE || TRA 140 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
144 select TRACING 141 select TRACING
145 default y 142 default y
146 help 143 help
147 Create preempt/irq toggle tracepoint 144 Create preempt/irq toggle tracepoints if needed, so that other parts
148 of the kernel can use them to genera 145 of the kernel can use them to generate or add hooks to them.
149 146
150 # All tracer options should select GENERIC_TRA 147 # All tracer options should select GENERIC_TRACER. For those options that are
151 # enabled by all tracers (context switch and e 148 # enabled by all tracers (context switch and event tracer) they select TRACING.
152 # This allows those options to appear when no 149 # This allows those options to appear when no other tracer is selected. But the
153 # options do not appear when something else se 150 # options do not appear when something else selects it. We need the two options
154 # GENERIC_TRACER and TRACING to avoid circular 151 # GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
155 # hiding of the automatic options. 152 # hiding of the automatic options.
156 153
157 config TRACING 154 config TRACING
158 bool 155 bool
159 select RING_BUFFER 156 select RING_BUFFER
160 select STACKTRACE if STACKTRACE_SUPPOR 157 select STACKTRACE if STACKTRACE_SUPPORT
161 select TRACEPOINTS 158 select TRACEPOINTS
162 select NOP_TRACER 159 select NOP_TRACER
163 select BINARY_PRINTF 160 select BINARY_PRINTF
164 select EVENT_TRACING 161 select EVENT_TRACING
165 select TRACE_CLOCK 162 select TRACE_CLOCK
166 select NEED_TASKS_RCU !! 163 select TASKS_RCU if PREEMPTION
167 164
168 config GENERIC_TRACER 165 config GENERIC_TRACER
169 bool 166 bool
170 select TRACING 167 select TRACING
171 168
172 # 169 #
173 # Minimum requirements an architecture has to 170 # Minimum requirements an architecture has to meet for us to
174 # be able to offer generic tracing facilities: 171 # be able to offer generic tracing facilities:
175 # 172 #
176 config TRACING_SUPPORT 173 config TRACING_SUPPORT
177 bool 174 bool
178 depends on TRACE_IRQFLAGS_SUPPORT 175 depends on TRACE_IRQFLAGS_SUPPORT
179 depends on STACKTRACE_SUPPORT 176 depends on STACKTRACE_SUPPORT
180 default y 177 default y
181 178
182 menuconfig FTRACE 179 menuconfig FTRACE
183 bool "Tracers" 180 bool "Tracers"
184 depends on TRACING_SUPPORT 181 depends on TRACING_SUPPORT
185 default y if DEBUG_KERNEL 182 default y if DEBUG_KERNEL
186 help 183 help
187 Enable the kernel tracing infrastruc 184 Enable the kernel tracing infrastructure.
188 185
189 if FTRACE 186 if FTRACE
190 187
191 config BOOTTIME_TRACING 188 config BOOTTIME_TRACING
192 bool "Boot-time Tracing support" 189 bool "Boot-time Tracing support"
193 depends on TRACING 190 depends on TRACING
194 select BOOT_CONFIG 191 select BOOT_CONFIG
195 help 192 help
196 Enable developer to setup ftrace sub 193 Enable developer to setup ftrace subsystem via supplemental
197 kernel cmdline at boot time for debu 194 kernel cmdline at boot time for debugging (tracing) driver
198 initialization and boot process. 195 initialization and boot process.
199 196
200 config FUNCTION_TRACER 197 config FUNCTION_TRACER
201 bool "Kernel Function Tracer" 198 bool "Kernel Function Tracer"
202 depends on HAVE_FUNCTION_TRACER 199 depends on HAVE_FUNCTION_TRACER
203 select KALLSYMS 200 select KALLSYMS
204 select GENERIC_TRACER 201 select GENERIC_TRACER
205 select CONTEXT_SWITCH_TRACER 202 select CONTEXT_SWITCH_TRACER
206 select GLOB 203 select GLOB
207 select NEED_TASKS_RCU !! 204 select TASKS_RCU if PREEMPTION
208 select TASKS_RUDE_RCU 205 select TASKS_RUDE_RCU
209 help 206 help
210 Enable the kernel to trace every ker 207 Enable the kernel to trace every kernel function. This is done
211 by using a compiler feature to inser 208 by using a compiler feature to insert a small, 5-byte No-Operation
212 instruction at the beginning of ever 209 instruction at the beginning of every kernel function, which NOP
213 sequence is then dynamically patched 210 sequence is then dynamically patched into a tracer call when
214 tracing is enabled by the administra 211 tracing is enabled by the administrator. If it's runtime disabled
215 (the bootup default), then the overh 212 (the bootup default), then the overhead of the instructions is very
216 small and not measurable even in mic 213 small and not measurable even in micro-benchmarks (at least on
217 x86, but may have impact on other ar 214 x86, but may have impact on other architectures).
218 215
219 config FUNCTION_GRAPH_TRACER 216 config FUNCTION_GRAPH_TRACER
220 bool "Kernel Function Graph Tracer" 217 bool "Kernel Function Graph Tracer"
221 depends on HAVE_FUNCTION_GRAPH_TRACER 218 depends on HAVE_FUNCTION_GRAPH_TRACER
222 depends on FUNCTION_TRACER 219 depends on FUNCTION_TRACER
223 depends on !X86_32 || !CC_OPTIMIZE_FOR 220 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
224 default y 221 default y
225 help 222 help
226 Enable the kernel to trace a functio 223 Enable the kernel to trace a function at both its return
227 and its entry. 224 and its entry.
228 Its first purpose is to trace the du 225 Its first purpose is to trace the duration of functions and
229 draw a call graph for each thread wi 226 draw a call graph for each thread with some information like
230 the return value. This is done by se 227 the return value. This is done by setting the current return
231 address on the current task structur 228 address on the current task structure into a stack of calls.
232 229
233 config FUNCTION_GRAPH_RETVAL <<
234 bool "Kernel Function Graph Return Val <<
235 depends on HAVE_FUNCTION_GRAPH_RETVAL <<
236 depends on FUNCTION_GRAPH_TRACER <<
237 default n <<
238 help <<
239 Support recording and printing the f <<
240 using function graph tracer. It can <<
241 that return errors. This feature is <<
242 enable it via the trace option funcg <<
243 See Documentation/trace/ftrace.rst <<
244 <<
245 config DYNAMIC_FTRACE 230 config DYNAMIC_FTRACE
246 bool "enable/disable function tracing 231 bool "enable/disable function tracing dynamically"
247 depends on FUNCTION_TRACER 232 depends on FUNCTION_TRACER
248 depends on HAVE_DYNAMIC_FTRACE 233 depends on HAVE_DYNAMIC_FTRACE
249 default y 234 default y
250 help 235 help
251 This option will modify all the call 236 This option will modify all the calls to function tracing
252 dynamically (will patch them out of 237 dynamically (will patch them out of the binary image and
253 replace them with a No-Op instructio 238 replace them with a No-Op instruction) on boot up. During
254 compile time, a table is made of all 239 compile time, a table is made of all the locations that ftrace
255 can function trace, and this table i 240 can function trace, and this table is linked into the kernel
256 image. When this is enabled, functio 241 image. When this is enabled, functions can be individually
257 enabled, and the functions not enabl 242 enabled, and the functions not enabled will not affect
258 performance of the system. 243 performance of the system.
259 244
260 See the files in /sys/kernel/tracing 245 See the files in /sys/kernel/tracing:
261 available_filter_functions 246 available_filter_functions
262 set_ftrace_filter 247 set_ftrace_filter
263 set_ftrace_notrace 248 set_ftrace_notrace
264 249
265 This way a CONFIG_FUNCTION_TRACER ke 250 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
266 otherwise has native performance as 251 otherwise has native performance as long as no tracing is active.
267 252
268 config DYNAMIC_FTRACE_WITH_REGS 253 config DYNAMIC_FTRACE_WITH_REGS
269 def_bool y 254 def_bool y
270 depends on DYNAMIC_FTRACE 255 depends on DYNAMIC_FTRACE
271 depends on HAVE_DYNAMIC_FTRACE_WITH_RE 256 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
272 257
273 config DYNAMIC_FTRACE_WITH_DIRECT_CALLS 258 config DYNAMIC_FTRACE_WITH_DIRECT_CALLS
274 def_bool y 259 def_bool y
275 depends on DYNAMIC_FTRACE_WITH_REGS || 260 depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
276 depends on HAVE_DYNAMIC_FTRACE_WITH_DI 261 depends on HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
277 262
278 config DYNAMIC_FTRACE_WITH_CALL_OPS 263 config DYNAMIC_FTRACE_WITH_CALL_OPS
279 def_bool y 264 def_bool y
280 depends on HAVE_DYNAMIC_FTRACE_WITH_CA 265 depends on HAVE_DYNAMIC_FTRACE_WITH_CALL_OPS
281 266
282 config DYNAMIC_FTRACE_WITH_ARGS 267 config DYNAMIC_FTRACE_WITH_ARGS
283 def_bool y 268 def_bool y
284 depends on DYNAMIC_FTRACE 269 depends on DYNAMIC_FTRACE
285 depends on HAVE_DYNAMIC_FTRACE_WITH_AR 270 depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS
286 271
287 config FPROBE 272 config FPROBE
288 bool "Kernel Function Probe (fprobe)" 273 bool "Kernel Function Probe (fprobe)"
289 depends on FUNCTION_TRACER 274 depends on FUNCTION_TRACER
290 depends on DYNAMIC_FTRACE_WITH_REGS 275 depends on DYNAMIC_FTRACE_WITH_REGS
291 depends on HAVE_RETHOOK 276 depends on HAVE_RETHOOK
292 select RETHOOK 277 select RETHOOK
293 default n 278 default n
294 help 279 help
295 This option enables kernel function 280 This option enables kernel function probe (fprobe) based on ftrace.
296 The fprobe is similar to kprobes, bu 281 The fprobe is similar to kprobes, but probes only for kernel function
297 entries and exits. This also can pro 282 entries and exits. This also can probe multiple functions by one
298 fprobe. 283 fprobe.
299 284
300 If unsure, say N. 285 If unsure, say N.
301 286
302 config FUNCTION_PROFILER 287 config FUNCTION_PROFILER
303 bool "Kernel function profiler" 288 bool "Kernel function profiler"
304 depends on FUNCTION_TRACER 289 depends on FUNCTION_TRACER
305 default n 290 default n
306 help 291 help
307 This option enables the kernel funct 292 This option enables the kernel function profiler. A file is created
308 in debugfs called function_profile_e 293 in debugfs called function_profile_enabled which defaults to zero.
309 When a 1 is echoed into this file pr 294 When a 1 is echoed into this file profiling begins, and when a
310 zero is entered, profiling stops. A 295 zero is entered, profiling stops. A "functions" file is created in
311 the trace_stat directory; this file 296 the trace_stat directory; this file shows the list of functions that
312 have been hit and their counters. 297 have been hit and their counters.
313 298
314 If in doubt, say N. 299 If in doubt, say N.
315 300
316 config STACK_TRACER 301 config STACK_TRACER
317 bool "Trace max stack" 302 bool "Trace max stack"
318 depends on HAVE_FUNCTION_TRACER 303 depends on HAVE_FUNCTION_TRACER
319 select FUNCTION_TRACER 304 select FUNCTION_TRACER
320 select STACKTRACE 305 select STACKTRACE
321 select KALLSYMS 306 select KALLSYMS
322 help 307 help
323 This special tracer records the maxi 308 This special tracer records the maximum stack footprint of the
324 kernel and displays it in /sys/kerne 309 kernel and displays it in /sys/kernel/tracing/stack_trace.
325 310
326 This tracer works by hooking into ev 311 This tracer works by hooking into every function call that the
327 kernel executes, and keeping a maxim 312 kernel executes, and keeping a maximum stack depth value and
328 stack-trace saved. If this is confi 313 stack-trace saved. If this is configured with DYNAMIC_FTRACE
329 then it will not have any overhead w 314 then it will not have any overhead while the stack tracer
330 is disabled. 315 is disabled.
331 316
332 To enable the stack tracer on bootup 317 To enable the stack tracer on bootup, pass in 'stacktrace'
333 on the kernel command line. 318 on the kernel command line.
334 319
335 The stack tracer can also be enabled 320 The stack tracer can also be enabled or disabled via the
336 sysctl kernel.stack_tracer_enabled 321 sysctl kernel.stack_tracer_enabled
337 322
338 Say N if unsure. 323 Say N if unsure.
339 324
340 config TRACE_PREEMPT_TOGGLE 325 config TRACE_PREEMPT_TOGGLE
341 bool 326 bool
342 help 327 help
343 Enables hooks which will be called w 328 Enables hooks which will be called when preemption is first disabled,
344 and last enabled. 329 and last enabled.
345 330
346 config IRQSOFF_TRACER 331 config IRQSOFF_TRACER
347 bool "Interrupts-off Latency Tracer" 332 bool "Interrupts-off Latency Tracer"
348 default n 333 default n
349 depends on TRACE_IRQFLAGS_SUPPORT 334 depends on TRACE_IRQFLAGS_SUPPORT
350 select TRACE_IRQFLAGS 335 select TRACE_IRQFLAGS
351 select GENERIC_TRACER 336 select GENERIC_TRACER
352 select TRACER_MAX_TRACE 337 select TRACER_MAX_TRACE
353 select RING_BUFFER_ALLOW_SWAP 338 select RING_BUFFER_ALLOW_SWAP
354 select TRACER_SNAPSHOT 339 select TRACER_SNAPSHOT
355 select TRACER_SNAPSHOT_PER_CPU_SWAP 340 select TRACER_SNAPSHOT_PER_CPU_SWAP
356 help 341 help
357 This option measures the time spent 342 This option measures the time spent in irqs-off critical
358 sections, with microsecond accuracy. 343 sections, with microsecond accuracy.
359 344
360 The default measurement method is a 345 The default measurement method is a maximum search, which is
361 disabled by default and can be runti 346 disabled by default and can be runtime (re-)started
362 via: 347 via:
363 348
364 echo 0 > /sys/kernel/tracing/tra 349 echo 0 > /sys/kernel/tracing/tracing_max_latency
365 350
366 (Note that kernel size and overhead 351 (Note that kernel size and overhead increase with this option
367 enabled. This option and the preempt 352 enabled. This option and the preempt-off timing option can be
368 used together or separately.) 353 used together or separately.)
369 354
370 config PREEMPT_TRACER 355 config PREEMPT_TRACER
371 bool "Preemption-off Latency Tracer" 356 bool "Preemption-off Latency Tracer"
372 default n 357 default n
373 depends on PREEMPTION 358 depends on PREEMPTION
374 select GENERIC_TRACER 359 select GENERIC_TRACER
375 select TRACER_MAX_TRACE 360 select TRACER_MAX_TRACE
376 select RING_BUFFER_ALLOW_SWAP 361 select RING_BUFFER_ALLOW_SWAP
377 select TRACER_SNAPSHOT 362 select TRACER_SNAPSHOT
378 select TRACER_SNAPSHOT_PER_CPU_SWAP 363 select TRACER_SNAPSHOT_PER_CPU_SWAP
379 select TRACE_PREEMPT_TOGGLE 364 select TRACE_PREEMPT_TOGGLE
380 help 365 help
381 This option measures the time spent 366 This option measures the time spent in preemption-off critical
382 sections, with microsecond accuracy. 367 sections, with microsecond accuracy.
383 368
384 The default measurement method is a 369 The default measurement method is a maximum search, which is
385 disabled by default and can be runti 370 disabled by default and can be runtime (re-)started
386 via: 371 via:
387 372
388 echo 0 > /sys/kernel/tracing/tra 373 echo 0 > /sys/kernel/tracing/tracing_max_latency
389 374
390 (Note that kernel size and overhead 375 (Note that kernel size and overhead increase with this option
391 enabled. This option and the irqs-of 376 enabled. This option and the irqs-off timing option can be
392 used together or separately.) 377 used together or separately.)
393 378
394 config SCHED_TRACER 379 config SCHED_TRACER
395 bool "Scheduling Latency Tracer" 380 bool "Scheduling Latency Tracer"
396 select GENERIC_TRACER 381 select GENERIC_TRACER
397 select CONTEXT_SWITCH_TRACER 382 select CONTEXT_SWITCH_TRACER
398 select TRACER_MAX_TRACE 383 select TRACER_MAX_TRACE
399 select TRACER_SNAPSHOT 384 select TRACER_SNAPSHOT
400 help 385 help
401 This tracer tracks the latency of th 386 This tracer tracks the latency of the highest priority task
402 to be scheduled in, starting from th 387 to be scheduled in, starting from the point it has woken up.
403 388
404 config HWLAT_TRACER 389 config HWLAT_TRACER
405 bool "Tracer to detect hardware latenc 390 bool "Tracer to detect hardware latencies (like SMIs)"
406 select GENERIC_TRACER 391 select GENERIC_TRACER
407 select TRACER_MAX_TRACE 392 select TRACER_MAX_TRACE
408 help 393 help
409 This tracer, when enabled will create 394 This tracer, when enabled will create one or more kernel threads,
410 depending on what the cpumask file is 395 depending on what the cpumask file is set to, which each thread
411 spinning in a loop looking for interr 396 spinning in a loop looking for interruptions caused by
412 something other than the kernel. For 397 something other than the kernel. For example, if a
413 System Management Interrupt (SMI) tak 398 System Management Interrupt (SMI) takes a noticeable amount of
414 time, this tracer will detect it. Thi 399 time, this tracer will detect it. This is useful for testing
415 if a system is reliable for Real Time 400 if a system is reliable for Real Time tasks.
416 401
417 Some files are created in the tracing 402 Some files are created in the tracing directory when this
418 is enabled: 403 is enabled:
419 404
420 hwlat_detector/width - time in us 405 hwlat_detector/width - time in usecs for how long to spin for
421 hwlat_detector/window - time in us 406 hwlat_detector/window - time in usecs between the start of each
422 iteration 407 iteration
423 408
424 A kernel thread is created that will 409 A kernel thread is created that will spin with interrupts disabled
425 for "width" microseconds in every "wi 410 for "width" microseconds in every "window" cycle. It will not spin
426 for "window - width" microseconds, wh 411 for "window - width" microseconds, where the system can
427 continue to operate. 412 continue to operate.
428 413
429 The output will appear in the trace a 414 The output will appear in the trace and trace_pipe files.
430 415
431 When the tracer is not running, it ha 416 When the tracer is not running, it has no affect on the system,
432 but when it is running, it can cause 417 but when it is running, it can cause the system to be
433 periodically non responsive. Do not r 418 periodically non responsive. Do not run this tracer on a
434 production system. 419 production system.
435 420
436 To enable this tracer, echo in "hwlat 421 To enable this tracer, echo in "hwlat" into the current_tracer
437 file. Every time a latency is greater 422 file. Every time a latency is greater than tracing_thresh, it will
438 be recorded into the ring buffer. 423 be recorded into the ring buffer.
439 424
440 config OSNOISE_TRACER 425 config OSNOISE_TRACER
441 bool "OS Noise tracer" 426 bool "OS Noise tracer"
442 select GENERIC_TRACER 427 select GENERIC_TRACER
443 select TRACER_MAX_TRACE 428 select TRACER_MAX_TRACE
444 help 429 help
445 In the context of high-performance c 430 In the context of high-performance computing (HPC), the Operating
446 System Noise (osnoise) refers to the 431 System Noise (osnoise) refers to the interference experienced by an
447 application due to activities inside 432 application due to activities inside the operating system. In the
448 context of Linux, NMIs, IRQs, SoftIR 433 context of Linux, NMIs, IRQs, SoftIRQs, and any other system thread
449 can cause noise to the system. Moreo 434 can cause noise to the system. Moreover, hardware-related jobs can
450 also cause noise, for example, via S 435 also cause noise, for example, via SMIs.
451 436
452 The osnoise tracer leverages the hwl 437 The osnoise tracer leverages the hwlat_detector by running a similar
453 loop with preemption, SoftIRQs and I 438 loop with preemption, SoftIRQs and IRQs enabled, thus allowing all
454 the sources of osnoise during its ex 439 the sources of osnoise during its execution. The osnoise tracer takes
455 note of the entry and exit point of 440 note of the entry and exit point of any source of interferences,
456 increasing a per-cpu interference co 441 increasing a per-cpu interference counter. It saves an interference
457 counter for each source of interfere 442 counter for each source of interference. The interference counter for
458 NMI, IRQs, SoftIRQs, and threads is 443 NMI, IRQs, SoftIRQs, and threads is increased anytime the tool
459 observes these interferences' entry 444 observes these interferences' entry events. When a noise happens
460 without any interference from the op 445 without any interference from the operating system level, the
461 hardware noise counter increases, po 446 hardware noise counter increases, pointing to a hardware-related
462 noise. In this way, osnoise can acco 447 noise. In this way, osnoise can account for any source of
463 interference. At the end of the peri 448 interference. At the end of the period, the osnoise tracer prints
464 the sum of all noise, the max single 449 the sum of all noise, the max single noise, the percentage of CPU
465 available for the thread, and the co 450 available for the thread, and the counters for the noise sources.
466 451
467 In addition to the tracer, a set of 452 In addition to the tracer, a set of tracepoints were added to
468 facilitate the identification of the 453 facilitate the identification of the osnoise source.
469 454
470 The output will appear in the trace 455 The output will appear in the trace and trace_pipe files.
471 456
472 To enable this tracer, echo in "osno 457 To enable this tracer, echo in "osnoise" into the current_tracer
473 file. 458 file.
474 459
475 config TIMERLAT_TRACER 460 config TIMERLAT_TRACER
476 bool "Timerlat tracer" 461 bool "Timerlat tracer"
477 select OSNOISE_TRACER 462 select OSNOISE_TRACER
478 select GENERIC_TRACER 463 select GENERIC_TRACER
479 help 464 help
480 The timerlat tracer aims to help the 465 The timerlat tracer aims to help the preemptive kernel developers
481 to find sources of wakeup latencies 466 to find sources of wakeup latencies of real-time threads.
482 467
483 The tracer creates a per-cpu kernel 468 The tracer creates a per-cpu kernel thread with real-time priority.
484 The tracer thread sets a periodic ti 469 The tracer thread sets a periodic timer to wakeup itself, and goes
485 to sleep waiting for the timer to fi 470 to sleep waiting for the timer to fire. At the wakeup, the thread
486 then computes a wakeup latency value 471 then computes a wakeup latency value as the difference between
487 the current time and the absolute ti 472 the current time and the absolute time that the timer was set
488 to expire. 473 to expire.
489 474
490 The tracer prints two lines at every 475 The tracer prints two lines at every activation. The first is the
491 timer latency observed at the hardir 476 timer latency observed at the hardirq context before the
492 activation of the thread. The second 477 activation of the thread. The second is the timer latency observed
493 by the thread, which is the same lev 478 by the thread, which is the same level that cyclictest reports. The
494 ACTIVATION ID field serves to relate 479 ACTIVATION ID field serves to relate the irq execution to its
495 respective thread execution. 480 respective thread execution.
496 481
497 The tracer is build on top of osnois 482 The tracer is build on top of osnoise tracer, and the osnoise:
498 events can be used to trace the sour 483 events can be used to trace the source of interference from NMI,
499 IRQs and other threads. It also enab 484 IRQs and other threads. It also enables the capture of the
500 stacktrace at the IRQ context, which 485 stacktrace at the IRQ context, which helps to identify the code
501 path that can cause thread delay. 486 path that can cause thread delay.
502 487
503 config MMIOTRACE 488 config MMIOTRACE
504 bool "Memory mapped IO tracing" 489 bool "Memory mapped IO tracing"
505 depends on HAVE_MMIOTRACE_SUPPORT && P 490 depends on HAVE_MMIOTRACE_SUPPORT && PCI
506 select GENERIC_TRACER 491 select GENERIC_TRACER
507 help 492 help
508 Mmiotrace traces Memory Mapped I/O a 493 Mmiotrace traces Memory Mapped I/O access and is meant for
509 debugging and reverse engineering. I 494 debugging and reverse engineering. It is called from the ioremap
510 implementation and works via page fa 495 implementation and works via page faults. Tracing is disabled by
511 default and can be enabled at run-ti 496 default and can be enabled at run-time.
512 497
513 See Documentation/trace/mmiotrace.rs 498 See Documentation/trace/mmiotrace.rst.
514 If you are not helping to develop dr 499 If you are not helping to develop drivers, say N.
515 500
516 config ENABLE_DEFAULT_TRACERS 501 config ENABLE_DEFAULT_TRACERS
517 bool "Trace process context switches a 502 bool "Trace process context switches and events"
518 depends on !GENERIC_TRACER 503 depends on !GENERIC_TRACER
519 select TRACING 504 select TRACING
520 help 505 help
521 This tracer hooks to various trace p 506 This tracer hooks to various trace points in the kernel,
522 allowing the user to pick and choose 507 allowing the user to pick and choose which trace point they
523 want to trace. It also includes the 508 want to trace. It also includes the sched_switch tracer plugin.
524 509
525 config FTRACE_SYSCALLS 510 config FTRACE_SYSCALLS
526 bool "Trace syscalls" 511 bool "Trace syscalls"
527 depends on HAVE_SYSCALL_TRACEPOINTS 512 depends on HAVE_SYSCALL_TRACEPOINTS
528 select GENERIC_TRACER 513 select GENERIC_TRACER
529 select KALLSYMS 514 select KALLSYMS
530 help 515 help
531 Basic tracer to catch the syscall en 516 Basic tracer to catch the syscall entry and exit events.
532 517
533 config TRACER_SNAPSHOT 518 config TRACER_SNAPSHOT
534 bool "Create a snapshot trace buffer" 519 bool "Create a snapshot trace buffer"
535 select TRACER_MAX_TRACE 520 select TRACER_MAX_TRACE
536 help 521 help
537 Allow tracing users to take snapshot 522 Allow tracing users to take snapshot of the current buffer using the
538 ftrace interface, e.g.: 523 ftrace interface, e.g.:
539 524
540 echo 1 > /sys/kernel/tracing/sna 525 echo 1 > /sys/kernel/tracing/snapshot
541 cat snapshot 526 cat snapshot
542 527
543 config TRACER_SNAPSHOT_PER_CPU_SWAP 528 config TRACER_SNAPSHOT_PER_CPU_SWAP
544 bool "Allow snapshot to swap per CPU" 529 bool "Allow snapshot to swap per CPU"
545 depends on TRACER_SNAPSHOT 530 depends on TRACER_SNAPSHOT
546 select RING_BUFFER_ALLOW_SWAP 531 select RING_BUFFER_ALLOW_SWAP
547 help 532 help
548 Allow doing a snapshot of a single C 533 Allow doing a snapshot of a single CPU buffer instead of a
549 full swap (all buffers). If this is 534 full swap (all buffers). If this is set, then the following is
550 allowed: 535 allowed:
551 536
552 echo 1 > /sys/kernel/tracing/per 537 echo 1 > /sys/kernel/tracing/per_cpu/cpu2/snapshot
553 538
554 After which, only the tracing buffer 539 After which, only the tracing buffer for CPU 2 was swapped with
555 the main tracing buffer, and the oth 540 the main tracing buffer, and the other CPU buffers remain the same.
556 541
557 When this is enabled, this adds a li 542 When this is enabled, this adds a little more overhead to the
558 trace recording, as it needs to add 543 trace recording, as it needs to add some checks to synchronize
559 recording with swaps. But this does 544 recording with swaps. But this does not affect the performance
560 of the overall system. This is enabl 545 of the overall system. This is enabled by default when the preempt
561 or irq latency tracers are enabled, 546 or irq latency tracers are enabled, as those need to swap as well
562 and already adds the overhead (plus 547 and already adds the overhead (plus a lot more).
563 548
564 config TRACE_BRANCH_PROFILING 549 config TRACE_BRANCH_PROFILING
565 bool 550 bool
566 select GENERIC_TRACER 551 select GENERIC_TRACER
567 552
568 choice 553 choice
569 prompt "Branch Profiling" 554 prompt "Branch Profiling"
570 default BRANCH_PROFILE_NONE 555 default BRANCH_PROFILE_NONE
571 help 556 help
572 The branch profiling is a software pr 557 The branch profiling is a software profiler. It will add hooks
573 into the C conditionals to test which 558 into the C conditionals to test which path a branch takes.
574 559
575 The likely/unlikely profiler only loo 560 The likely/unlikely profiler only looks at the conditions that
576 are annotated with a likely or unlike 561 are annotated with a likely or unlikely macro.
577 562
578 The "all branch" profiler will profil 563 The "all branch" profiler will profile every if-statement in the
579 kernel. This profiler will also enabl 564 kernel. This profiler will also enable the likely/unlikely
580 profiler. 565 profiler.
581 566
582 Either of the above profilers adds a 567 Either of the above profilers adds a bit of overhead to the system.
583 If unsure, choose "No branch profilin 568 If unsure, choose "No branch profiling".
584 569
585 config BRANCH_PROFILE_NONE 570 config BRANCH_PROFILE_NONE
586 bool "No branch profiling" 571 bool "No branch profiling"
587 help 572 help
588 No branch profiling. Branch profilin 573 No branch profiling. Branch profiling adds a bit of overhead.
589 Only enable it if you want to analys 574 Only enable it if you want to analyse the branching behavior.
590 Otherwise keep it disabled. 575 Otherwise keep it disabled.
591 576
592 config PROFILE_ANNOTATED_BRANCHES 577 config PROFILE_ANNOTATED_BRANCHES
593 bool "Trace likely/unlikely profiler" 578 bool "Trace likely/unlikely profiler"
594 select TRACE_BRANCH_PROFILING 579 select TRACE_BRANCH_PROFILING
595 help 580 help
596 This tracer profiles all likely and 581 This tracer profiles all likely and unlikely macros
597 in the kernel. It will display the r 582 in the kernel. It will display the results in:
598 583
599 /sys/kernel/tracing/trace_stat/branc 584 /sys/kernel/tracing/trace_stat/branch_annotated
600 585
601 Note: this will add a significant ov 586 Note: this will add a significant overhead; only turn this
602 on if you need to profile the system 587 on if you need to profile the system's use of these macros.
603 588
604 config PROFILE_ALL_BRANCHES 589 config PROFILE_ALL_BRANCHES
605 bool "Profile all if conditionals" if 590 bool "Profile all if conditionals" if !FORTIFY_SOURCE
606 select TRACE_BRANCH_PROFILING 591 select TRACE_BRANCH_PROFILING
607 help 592 help
608 This tracer profiles all branch cond 593 This tracer profiles all branch conditions. Every if ()
609 taken in the kernel is recorded whet 594 taken in the kernel is recorded whether it hit or miss.
610 The results will be displayed in: 595 The results will be displayed in:
611 596
612 /sys/kernel/tracing/trace_stat/branc 597 /sys/kernel/tracing/trace_stat/branch_all
613 598
614 This option also enables the likely/ 599 This option also enables the likely/unlikely profiler.
615 600
616 This configuration, when enabled, wi 601 This configuration, when enabled, will impose a great overhead
617 on the system. This should only be e 602 on the system. This should only be enabled when the system
618 is to be analyzed in much detail. 603 is to be analyzed in much detail.
619 endchoice 604 endchoice
620 605
621 config TRACING_BRANCHES 606 config TRACING_BRANCHES
622 bool 607 bool
623 help 608 help
624 Selected by tracers that will trace 609 Selected by tracers that will trace the likely and unlikely
625 conditions. This prevents the tracer 610 conditions. This prevents the tracers themselves from being
626 profiled. Profiling the tracing infr 611 profiled. Profiling the tracing infrastructure can only happen
627 when the likelys and unlikelys are n 612 when the likelys and unlikelys are not being traced.
628 613
629 config BRANCH_TRACER 614 config BRANCH_TRACER
630 bool "Trace likely/unlikely instances" 615 bool "Trace likely/unlikely instances"
631 depends on TRACE_BRANCH_PROFILING 616 depends on TRACE_BRANCH_PROFILING
632 select TRACING_BRANCHES 617 select TRACING_BRANCHES
633 help 618 help
634 This traces the events of likely and 619 This traces the events of likely and unlikely condition
635 calls in the kernel. The difference 620 calls in the kernel. The difference between this and the
636 "Trace likely/unlikely profiler" is 621 "Trace likely/unlikely profiler" is that this is not a
637 histogram of the callers, but actual 622 histogram of the callers, but actually places the calling
638 events into a running trace buffer t 623 events into a running trace buffer to see when and where the
639 events happened, as well as their re 624 events happened, as well as their results.
640 625
641 Say N if unsure. 626 Say N if unsure.
642 627
643 config BLK_DEV_IO_TRACE 628 config BLK_DEV_IO_TRACE
644 bool "Support for tracing block IO act 629 bool "Support for tracing block IO actions"
645 depends on SYSFS 630 depends on SYSFS
646 depends on BLOCK 631 depends on BLOCK
647 select RELAY 632 select RELAY
648 select DEBUG_FS 633 select DEBUG_FS
649 select TRACEPOINTS 634 select TRACEPOINTS
650 select GENERIC_TRACER 635 select GENERIC_TRACER
651 select STACKTRACE 636 select STACKTRACE
652 help 637 help
653 Say Y here if you want to be able to 638 Say Y here if you want to be able to trace the block layer actions
654 on a given queue. Tracing allows you 639 on a given queue. Tracing allows you to see any traffic happening
655 on a block device queue. For more in 640 on a block device queue. For more information (and the userspace
656 support tools needed), fetch the blk 641 support tools needed), fetch the blktrace tools from:
657 642
658 git://git.kernel.dk/blktrace.git 643 git://git.kernel.dk/blktrace.git
659 644
660 Tracing also is possible using the f 645 Tracing also is possible using the ftrace interface, e.g.:
661 646
662 echo 1 > /sys/block/sda/sda1/trace 647 echo 1 > /sys/block/sda/sda1/trace/enable
663 echo blk > /sys/kernel/tracing/cur 648 echo blk > /sys/kernel/tracing/current_tracer
664 cat /sys/kernel/tracing/trace_pipe 649 cat /sys/kernel/tracing/trace_pipe
665 650
666 If unsure, say N. 651 If unsure, say N.
667 652
668 config FPROBE_EVENTS <<
669 depends on FPROBE <<
670 depends on HAVE_REGS_AND_STACK_ACCESS_ <<
671 bool "Enable fprobe-based dynamic even <<
672 select TRACING <<
673 select PROBE_EVENTS <<
674 select DYNAMIC_EVENTS <<
675 default y <<
676 help <<
677 This allows user to add tracing even <<
678 exit via ftrace interface. The synta <<
679 and the kprobe events on function en <<
680 transparently converted to this fpro <<
681 <<
682 config PROBE_EVENTS_BTF_ARGS <<
683 depends on HAVE_FUNCTION_ARG_ACCESS_AP <<
684 depends on FPROBE_EVENTS || KPROBE_EVE <<
685 depends on DEBUG_INFO_BTF && BPF_SYSCA <<
686 bool "Support BTF function arguments f <<
687 default y <<
688 help <<
689 The user can specify the arguments o <<
690 of the arguments of the probed funct <<
691 kernel function entry or a tracepoin <<
692 This is available only if BTF (BPF T <<
693 <<
694 config KPROBE_EVENTS 653 config KPROBE_EVENTS
695 depends on KPROBES 654 depends on KPROBES
696 depends on HAVE_REGS_AND_STACK_ACCESS_ 655 depends on HAVE_REGS_AND_STACK_ACCESS_API
697 bool "Enable kprobes-based dynamic eve 656 bool "Enable kprobes-based dynamic events"
698 select TRACING 657 select TRACING
699 select PROBE_EVENTS 658 select PROBE_EVENTS
700 select DYNAMIC_EVENTS 659 select DYNAMIC_EVENTS
701 default y 660 default y
702 help 661 help
703 This allows the user to add tracing 662 This allows the user to add tracing events (similar to tracepoints)
704 on the fly via the ftrace interface. 663 on the fly via the ftrace interface. See
705 Documentation/trace/kprobetrace.rst 664 Documentation/trace/kprobetrace.rst for more details.
706 665
707 Those events can be inserted whereve 666 Those events can be inserted wherever kprobes can probe, and record
708 various register and memory values. 667 various register and memory values.
709 668
710 This option is also required by perf 669 This option is also required by perf-probe subcommand of perf tools.
711 If you want to use perf tools, this 670 If you want to use perf tools, this option is strongly recommended.
712 671
713 config KPROBE_EVENTS_ON_NOTRACE 672 config KPROBE_EVENTS_ON_NOTRACE
714 bool "Do NOT protect notrace function 673 bool "Do NOT protect notrace function from kprobe events"
715 depends on KPROBE_EVENTS 674 depends on KPROBE_EVENTS
716 depends on DYNAMIC_FTRACE 675 depends on DYNAMIC_FTRACE
717 default n 676 default n
718 help 677 help
719 This is only for the developers who 678 This is only for the developers who want to debug ftrace itself
720 using kprobe events. 679 using kprobe events.
721 680
722 If kprobes can use ftrace instead of 681 If kprobes can use ftrace instead of breakpoint, ftrace related
723 functions are protected from kprobe- 682 functions are protected from kprobe-events to prevent an infinite
724 recursion or any unexpected executio 683 recursion or any unexpected execution path which leads to a kernel
725 crash. 684 crash.
726 685
727 This option disables such protection 686 This option disables such protection and allows you to put kprobe
728 events on ftrace functions for debug 687 events on ftrace functions for debugging ftrace by itself.
729 Note that this might let you shoot y 688 Note that this might let you shoot yourself in the foot.
730 689
731 If unsure, say N. 690 If unsure, say N.
732 691
733 config UPROBE_EVENTS 692 config UPROBE_EVENTS
734 bool "Enable uprobes-based dynamic eve 693 bool "Enable uprobes-based dynamic events"
735 depends on ARCH_SUPPORTS_UPROBES 694 depends on ARCH_SUPPORTS_UPROBES
736 depends on MMU 695 depends on MMU
737 depends on PERF_EVENTS 696 depends on PERF_EVENTS
738 select UPROBES 697 select UPROBES
739 select PROBE_EVENTS 698 select PROBE_EVENTS
740 select DYNAMIC_EVENTS 699 select DYNAMIC_EVENTS
741 select TRACING 700 select TRACING
742 default y 701 default y
743 help 702 help
744 This allows the user to add tracing 703 This allows the user to add tracing events on top of userspace
745 dynamic events (similar to tracepoin 704 dynamic events (similar to tracepoints) on the fly via the trace
746 events interface. Those events can b 705 events interface. Those events can be inserted wherever uprobes
747 can probe, and record various regist 706 can probe, and record various registers.
748 This option is required if you plan 707 This option is required if you plan to use perf-probe subcommand
749 of perf tools on user space applicat 708 of perf tools on user space applications.
750 709
751 config BPF_EVENTS 710 config BPF_EVENTS
752 depends on BPF_SYSCALL 711 depends on BPF_SYSCALL
753 depends on (KPROBE_EVENTS || UPROBE_EV 712 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
754 bool 713 bool
755 default y 714 default y
756 help 715 help
757 This allows the user to attach BPF p 716 This allows the user to attach BPF programs to kprobe, uprobe, and
758 tracepoint events. 717 tracepoint events.
759 718
760 config DYNAMIC_EVENTS 719 config DYNAMIC_EVENTS
761 def_bool n 720 def_bool n
762 721
763 config PROBE_EVENTS 722 config PROBE_EVENTS
764 def_bool n 723 def_bool n
765 724
766 config BPF_KPROBE_OVERRIDE 725 config BPF_KPROBE_OVERRIDE
767 bool "Enable BPF programs to override 726 bool "Enable BPF programs to override a kprobed function"
768 depends on BPF_EVENTS 727 depends on BPF_EVENTS
769 depends on FUNCTION_ERROR_INJECTION 728 depends on FUNCTION_ERROR_INJECTION
770 default n 729 default n
771 help 730 help
772 Allows BPF to override the execution 731 Allows BPF to override the execution of a probed function and
773 set a different return value. This i 732 set a different return value. This is used for error injection.
774 733
775 config FTRACE_MCOUNT_RECORD 734 config FTRACE_MCOUNT_RECORD
776 def_bool y 735 def_bool y
777 depends on DYNAMIC_FTRACE 736 depends on DYNAMIC_FTRACE
778 depends on HAVE_FTRACE_MCOUNT_RECORD 737 depends on HAVE_FTRACE_MCOUNT_RECORD
779 738
780 config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_EN 739 config FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
781 bool 740 bool
782 depends on FTRACE_MCOUNT_RECORD 741 depends on FTRACE_MCOUNT_RECORD
783 742
784 config FTRACE_MCOUNT_USE_CC 743 config FTRACE_MCOUNT_USE_CC
785 def_bool y 744 def_bool y
786 depends on $(cc-option,-mrecord-mcount 745 depends on $(cc-option,-mrecord-mcount)
787 depends on !FTRACE_MCOUNT_USE_PATCHABL 746 depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
788 depends on FTRACE_MCOUNT_RECORD 747 depends on FTRACE_MCOUNT_RECORD
789 748
790 config FTRACE_MCOUNT_USE_OBJTOOL 749 config FTRACE_MCOUNT_USE_OBJTOOL
791 def_bool y 750 def_bool y
792 depends on HAVE_OBJTOOL_MCOUNT 751 depends on HAVE_OBJTOOL_MCOUNT
793 depends on !FTRACE_MCOUNT_USE_PATCHABL 752 depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
794 depends on !FTRACE_MCOUNT_USE_CC 753 depends on !FTRACE_MCOUNT_USE_CC
795 depends on FTRACE_MCOUNT_RECORD 754 depends on FTRACE_MCOUNT_RECORD
796 select OBJTOOL 755 select OBJTOOL
797 756
798 config FTRACE_MCOUNT_USE_RECORDMCOUNT 757 config FTRACE_MCOUNT_USE_RECORDMCOUNT
799 def_bool y 758 def_bool y
800 depends on !FTRACE_MCOUNT_USE_PATCHABL 759 depends on !FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY
801 depends on !FTRACE_MCOUNT_USE_CC 760 depends on !FTRACE_MCOUNT_USE_CC
802 depends on !FTRACE_MCOUNT_USE_OBJTOOL 761 depends on !FTRACE_MCOUNT_USE_OBJTOOL
803 depends on FTRACE_MCOUNT_RECORD 762 depends on FTRACE_MCOUNT_RECORD
804 763
805 config TRACING_MAP 764 config TRACING_MAP
806 bool 765 bool
807 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG 766 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
808 help 767 help
809 tracing_map is a special-purpose loc 768 tracing_map is a special-purpose lock-free map for tracing,
810 separated out as a stand-alone facil 769 separated out as a stand-alone facility in order to allow it
811 to be shared between multiple tracer 770 to be shared between multiple tracers. It isn't meant to be
812 generally used outside of that conte 771 generally used outside of that context, and is normally
813 selected by tracers that use it. 772 selected by tracers that use it.
814 773
815 config SYNTH_EVENTS 774 config SYNTH_EVENTS
816 bool "Synthetic trace events" 775 bool "Synthetic trace events"
817 select TRACING 776 select TRACING
818 select DYNAMIC_EVENTS 777 select DYNAMIC_EVENTS
819 default n 778 default n
820 help 779 help
821 Synthetic events are user-defined tr 780 Synthetic events are user-defined trace events that can be
822 used to combine data from other trac 781 used to combine data from other trace events or in fact any
823 data source. Synthetic events can b 782 data source. Synthetic events can be generated indirectly
824 via the trace() action of histogram 783 via the trace() action of histogram triggers or directly
825 by way of an in-kernel API. 784 by way of an in-kernel API.
826 785
827 See Documentation/trace/events.rst o 786 See Documentation/trace/events.rst or
828 Documentation/trace/histogram.rst fo 787 Documentation/trace/histogram.rst for details and examples.
829 788
830 If in doubt, say N. 789 If in doubt, say N.
831 790
832 config USER_EVENTS 791 config USER_EVENTS
833 bool "User trace events" 792 bool "User trace events"
834 select TRACING 793 select TRACING
835 select DYNAMIC_EVENTS 794 select DYNAMIC_EVENTS
836 help 795 help
837 User trace events are user-defined t 796 User trace events are user-defined trace events that
838 can be used like an existing kernel 797 can be used like an existing kernel trace event. User trace
839 events are generated by writing to a 798 events are generated by writing to a tracefs file. User
840 processes can determine if their tra 799 processes can determine if their tracing events should be
841 generated by registering a value and 800 generated by registering a value and bit with the kernel
842 that reflects when it is enabled or 801 that reflects when it is enabled or not.
843 802
844 See Documentation/trace/user_events. 803 See Documentation/trace/user_events.rst.
845 If in doubt, say N. 804 If in doubt, say N.
846 805
847 config HIST_TRIGGERS 806 config HIST_TRIGGERS
848 bool "Histogram triggers" 807 bool "Histogram triggers"
849 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG 808 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
850 select TRACING_MAP 809 select TRACING_MAP
851 select TRACING 810 select TRACING
852 select DYNAMIC_EVENTS 811 select DYNAMIC_EVENTS
853 select SYNTH_EVENTS 812 select SYNTH_EVENTS
854 default n 813 default n
855 help 814 help
856 Hist triggers allow one or more arbi 815 Hist triggers allow one or more arbitrary trace event fields
857 to be aggregated into hash tables an 816 to be aggregated into hash tables and dumped to stdout by
858 reading a debugfs/tracefs file. The 817 reading a debugfs/tracefs file. They're useful for
859 gathering quick and dirty (though pr 818 gathering quick and dirty (though precise) summaries of
860 event activity as an initial guide f 819 event activity as an initial guide for further investigation
861 using more advanced tools. 820 using more advanced tools.
862 821
863 Inter-event tracing of quantities su 822 Inter-event tracing of quantities such as latencies is also
864 supported using hist triggers under 823 supported using hist triggers under this option.
865 824
866 See Documentation/trace/histogram.rs 825 See Documentation/trace/histogram.rst.
867 If in doubt, say N. 826 If in doubt, say N.
868 827
869 config TRACE_EVENT_INJECT 828 config TRACE_EVENT_INJECT
870 bool "Trace event injection" 829 bool "Trace event injection"
871 depends on TRACING 830 depends on TRACING
872 help 831 help
873 Allow user-space to inject a specifi 832 Allow user-space to inject a specific trace event into the ring
874 buffer. This is mainly used for test 833 buffer. This is mainly used for testing purpose.
875 834
876 If unsure, say N. 835 If unsure, say N.
877 836
878 config TRACEPOINT_BENCHMARK 837 config TRACEPOINT_BENCHMARK
879 bool "Add tracepoint that benchmarks t 838 bool "Add tracepoint that benchmarks tracepoints"
880 help 839 help
881 This option creates the tracepoint "b 840 This option creates the tracepoint "benchmark:benchmark_event".
882 When the tracepoint is enabled, it ki 841 When the tracepoint is enabled, it kicks off a kernel thread that
883 goes into an infinite loop (calling c 842 goes into an infinite loop (calling cond_resched() to let other tasks
884 run), and calls the tracepoint. Each 843 run), and calls the tracepoint. Each iteration will record the time
885 it took to write to the tracepoint an 844 it took to write to the tracepoint and the next iteration that
886 data will be passed to the tracepoint 845 data will be passed to the tracepoint itself. That is, the tracepoint
887 will report the time it took to do th 846 will report the time it took to do the previous tracepoint.
888 The string written to the tracepoint 847 The string written to the tracepoint is a static string of 128 bytes
889 to keep the time the same. The initia 848 to keep the time the same. The initial string is simply a write of
890 "START". The second string records th 849 "START". The second string records the cold cache time of the first
891 write which is not added to the rest 850 write which is not added to the rest of the calculations.
892 851
893 As it is a tight loop, it benchmarks 852 As it is a tight loop, it benchmarks as hot cache. That's fine because
894 we care most about hot paths that are 853 we care most about hot paths that are probably in cache already.
895 854
896 An example of the output: 855 An example of the output:
897 856
898 START 857 START
899 first=3672 [COLD CACHED] 858 first=3672 [COLD CACHED]
900 last=632 first=3672 max=632 min= 859 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
901 last=278 first=3672 max=632 min= 860 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
902 last=277 first=3672 max=632 min= 861 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
903 last=273 first=3672 max=632 min= 862 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
904 last=273 first=3672 max=632 min= 863 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
905 last=281 first=3672 max=632 min= 864 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
906 865
907 866
908 config RING_BUFFER_BENCHMARK 867 config RING_BUFFER_BENCHMARK
909 tristate "Ring buffer benchmark stress 868 tristate "Ring buffer benchmark stress tester"
910 depends on RING_BUFFER 869 depends on RING_BUFFER
911 help 870 help
912 This option creates a test to stress 871 This option creates a test to stress the ring buffer and benchmark it.
913 It creates its own ring buffer such 872 It creates its own ring buffer such that it will not interfere with
914 any other users of the ring buffer ( 873 any other users of the ring buffer (such as ftrace). It then creates
915 a producer and consumer that will ru 874 a producer and consumer that will run for 10 seconds and sleep for
916 10 seconds. Each interval it will pr 875 10 seconds. Each interval it will print out the number of events
917 it recorded and give a rough estimat 876 it recorded and give a rough estimate of how long each iteration took.
918 877
919 It does not disable interrupts or ra 878 It does not disable interrupts or raise its priority, so it may be
920 affected by processes that are runni 879 affected by processes that are running.
921 880
922 If unsure, say N. 881 If unsure, say N.
923 882
924 config TRACE_EVAL_MAP_FILE 883 config TRACE_EVAL_MAP_FILE
925 bool "Show eval mappings for trace even 884 bool "Show eval mappings for trace events"
926 depends on TRACING 885 depends on TRACING
927 help 886 help
928 The "print fmt" of the trace events wi 887 The "print fmt" of the trace events will show the enum/sizeof names
929 instead of their values. This can caus 888 instead of their values. This can cause problems for user space tools
930 that use this string to parse the raw 889 that use this string to parse the raw data as user space does not know
931 how to convert the string to its value 890 how to convert the string to its value.
932 891
933 To fix this, there's a special macro i 892 To fix this, there's a special macro in the kernel that can be used
934 to convert an enum/sizeof into its val 893 to convert an enum/sizeof into its value. If this macro is used, then
935 the print fmt strings will be converte 894 the print fmt strings will be converted to their values.
936 895
937 If something does not get converted pr 896 If something does not get converted properly, this option can be
938 used to show what enums/sizeof the ker 897 used to show what enums/sizeof the kernel tried to convert.
939 898
940 This option is for debugging the conve 899 This option is for debugging the conversions. A file is created
941 in the tracing directory called "eval_ 900 in the tracing directory called "eval_map" that will show the
942 names matched with their values and wh 901 names matched with their values and what trace event system they
943 belong too. 902 belong too.
944 903
945 Normally, the mapping of the strings t 904 Normally, the mapping of the strings to values will be freed after
946 boot up or module load. With this opti 905 boot up or module load. With this option, they will not be freed, as
947 they are needed for the "eval_map" fil 906 they are needed for the "eval_map" file. Enabling this option will
948 increase the memory footprint of the r 907 increase the memory footprint of the running kernel.
949 908
950 If unsure, say N. 909 If unsure, say N.
951 910
952 config FTRACE_RECORD_RECURSION 911 config FTRACE_RECORD_RECURSION
953 bool "Record functions that recurse in 912 bool "Record functions that recurse in function tracing"
954 depends on FUNCTION_TRACER 913 depends on FUNCTION_TRACER
955 help 914 help
956 All callbacks that attach to the fun 915 All callbacks that attach to the function tracing have some sort
957 of protection against recursion. Eve 916 of protection against recursion. Even though the protection exists,
958 it adds overhead. This option will c 917 it adds overhead. This option will create a file in the tracefs
959 file system called "recursed_functio 918 file system called "recursed_functions" that will list the functions
960 that triggered a recursion. 919 that triggered a recursion.
961 920
962 This will add more overhead to cases 921 This will add more overhead to cases that have recursion.
963 922
964 If unsure, say N 923 If unsure, say N
965 924
966 config FTRACE_RECORD_RECURSION_SIZE 925 config FTRACE_RECORD_RECURSION_SIZE
967 int "Max number of recursed functions 926 int "Max number of recursed functions to record"
968 default 128 !! 927 default 128
969 depends on FTRACE_RECORD_RECURSION 928 depends on FTRACE_RECORD_RECURSION
970 help 929 help
971 This defines the limit of number of 930 This defines the limit of number of functions that can be
972 listed in the "recursed_functions" f 931 listed in the "recursed_functions" file, that lists all
973 the functions that caused a recursio 932 the functions that caused a recursion to happen.
974 This file can be reset, but the limi 933 This file can be reset, but the limit can not change in
975 size at runtime. 934 size at runtime.
976 935
977 config FTRACE_VALIDATE_RCU_IS_WATCHING <<
978 bool "Validate RCU is on during ftrace <<
979 depends on FUNCTION_TRACER <<
980 depends on ARCH_WANTS_NO_INSTR <<
981 help <<
982 All callbacks that attach to the fun <<
983 protection against recursion. This o <<
984 ftrace (and other users of ftrace_te <<
985 called outside of RCU, as if they ar <<
986 also has a noticeable overhead when <<
987 <<
988 If unsure, say N <<
989 <<
990 config RING_BUFFER_RECORD_RECURSION 936 config RING_BUFFER_RECORD_RECURSION
991 bool "Record functions that recurse in 937 bool "Record functions that recurse in the ring buffer"
992 depends on FTRACE_RECORD_RECURSION 938 depends on FTRACE_RECORD_RECURSION
993 # default y, because it is coupled wit 939 # default y, because it is coupled with FTRACE_RECORD_RECURSION
994 default y 940 default y
995 help 941 help
996 The ring buffer has its own internal 942 The ring buffer has its own internal recursion. Although when
997 recursion happens it won't cause har 943 recursion happens it won't cause harm because of the protection,
998 but it does cause unwanted overhead. 944 but it does cause unwanted overhead. Enabling this option will
999 place where recursion was detected i 945 place where recursion was detected into the ftrace "recursed_functions"
1000 file. 946 file.
1001 947
1002 This will add more overhead to case 948 This will add more overhead to cases that have recursion.
1003 949
1004 config GCOV_PROFILE_FTRACE 950 config GCOV_PROFILE_FTRACE
1005 bool "Enable GCOV profiling on ftrace 951 bool "Enable GCOV profiling on ftrace subsystem"
1006 depends on GCOV_KERNEL 952 depends on GCOV_KERNEL
1007 help 953 help
1008 Enable GCOV profiling on ftrace sub 954 Enable GCOV profiling on ftrace subsystem for checking
1009 which functions/lines are tested. 955 which functions/lines are tested.
1010 956
1011 If unsure, say N. 957 If unsure, say N.
1012 958
1013 Note that on a kernel compiled with 959 Note that on a kernel compiled with this config, ftrace will
1014 run significantly slower. 960 run significantly slower.
1015 961
1016 config FTRACE_SELFTEST 962 config FTRACE_SELFTEST
1017 bool 963 bool
1018 964
1019 config FTRACE_STARTUP_TEST 965 config FTRACE_STARTUP_TEST
1020 bool "Perform a startup test on ftrac 966 bool "Perform a startup test on ftrace"
1021 depends on GENERIC_TRACER 967 depends on GENERIC_TRACER
1022 select FTRACE_SELFTEST 968 select FTRACE_SELFTEST
1023 help 969 help
1024 This option performs a series of st 970 This option performs a series of startup tests on ftrace. On bootup
1025 a series of tests are made to verif 971 a series of tests are made to verify that the tracer is
1026 functioning properly. It will do te 972 functioning properly. It will do tests on all the configured
1027 tracers of ftrace. 973 tracers of ftrace.
1028 974
1029 config EVENT_TRACE_STARTUP_TEST 975 config EVENT_TRACE_STARTUP_TEST
1030 bool "Run selftest on trace events" 976 bool "Run selftest on trace events"
1031 depends on FTRACE_STARTUP_TEST 977 depends on FTRACE_STARTUP_TEST
1032 default y 978 default y
1033 help 979 help
1034 This option performs a test on all 980 This option performs a test on all trace events in the system.
1035 It basically just enables each even 981 It basically just enables each event and runs some code that
1036 will trigger events (not necessaril 982 will trigger events (not necessarily the event it enables)
1037 This may take some time run as ther 983 This may take some time run as there are a lot of events.
1038 984
1039 config EVENT_TRACE_TEST_SYSCALLS 985 config EVENT_TRACE_TEST_SYSCALLS
1040 bool "Run selftest on syscall events" 986 bool "Run selftest on syscall events"
1041 depends on EVENT_TRACE_STARTUP_TEST 987 depends on EVENT_TRACE_STARTUP_TEST
1042 help 988 help
1043 This option will also enable testing 989 This option will also enable testing every syscall event.
1044 It only enables the event and disabl 990 It only enables the event and disables it and runs various loads
1045 with the event enabled. This adds a 991 with the event enabled. This adds a bit more time for kernel boot
1046 up since it runs this on every syste 992 up since it runs this on every system call defined.
1047 993
1048 TBD - enable a way to actually call 994 TBD - enable a way to actually call the syscalls as we test their
1049 events 995 events
1050 996
1051 config FTRACE_SORT_STARTUP_TEST 997 config FTRACE_SORT_STARTUP_TEST
1052 bool "Verify compile time sorting of f 998 bool "Verify compile time sorting of ftrace functions"
1053 depends on DYNAMIC_FTRACE 999 depends on DYNAMIC_FTRACE
1054 depends on BUILDTIME_MCOUNT_SORT 1000 depends on BUILDTIME_MCOUNT_SORT
1055 help 1001 help
1056 Sorting of the mcount_loc sections t 1002 Sorting of the mcount_loc sections that is used to find the
1057 where the ftrace knows where to patc 1003 where the ftrace knows where to patch functions for tracing
1058 and other callbacks is done at compi 1004 and other callbacks is done at compile time. But if the sort
1059 is not done correctly, it will cause 1005 is not done correctly, it will cause non-deterministic failures.
1060 When this is set, the sorted section 1006 When this is set, the sorted sections will be verified that they
1061 are in deed sorted and will warn if 1007 are in deed sorted and will warn if they are not.
1062 1008
1063 If unsure, say N 1009 If unsure, say N
1064 1010
1065 config RING_BUFFER_STARTUP_TEST 1011 config RING_BUFFER_STARTUP_TEST
1066 bool "Ring buffer startup self test" 1012 bool "Ring buffer startup self test"
1067 depends on RING_BUFFER 1013 depends on RING_BUFFER
1068 help 1014 help
1069 Run a simple self test on the ring b 1015 Run a simple self test on the ring buffer on boot up. Late in the
1070 kernel boot sequence, the test will 1016 kernel boot sequence, the test will start that kicks off
1071 a thread per cpu. Each thread will w 1017 a thread per cpu. Each thread will write various size events
1072 into the ring buffer. Another thread 1018 into the ring buffer. Another thread is created to send IPIs
1073 to each of the threads, where the IP 1019 to each of the threads, where the IPI handler will also write
1074 to the ring buffer, to test/stress t 1020 to the ring buffer, to test/stress the nesting ability.
1075 If any anomalies are discovered, a w 1021 If any anomalies are discovered, a warning will be displayed
1076 and all ring buffers will be disable 1022 and all ring buffers will be disabled.
1077 1023
1078 The test runs for 10 seconds. This w 1024 The test runs for 10 seconds. This will slow your boot time
1079 by at least 10 more seconds. 1025 by at least 10 more seconds.
1080 1026
1081 At the end of the test, statistics a 1027 At the end of the test, statistics and more checks are done.
1082 It will output the stats of each per 1028 It will output the stats of each per cpu buffer: What
1083 was written, the sizes, what was rea 1029 was written, the sizes, what was read, what was lost, and
1084 other similar details. 1030 other similar details.
1085 1031
1086 If unsure, say N 1032 If unsure, say N
1087 1033
1088 config RING_BUFFER_VALIDATE_TIME_DELTAS 1034 config RING_BUFFER_VALIDATE_TIME_DELTAS
1089 bool "Verify ring buffer time stamp d 1035 bool "Verify ring buffer time stamp deltas"
1090 depends on RING_BUFFER 1036 depends on RING_BUFFER
1091 help 1037 help
1092 This will audit the time stamps on 1038 This will audit the time stamps on the ring buffer sub
1093 buffer to make sure that all the ti 1039 buffer to make sure that all the time deltas for the
1094 events on a sub buffer matches the 1040 events on a sub buffer matches the current time stamp.
1095 This audit is performed for every e 1041 This audit is performed for every event that is not
1096 interrupted, or interrupting anothe 1042 interrupted, or interrupting another event. A check
1097 is also made when traversing sub bu 1043 is also made when traversing sub buffers to make sure
1098 that all the deltas on the previous 1044 that all the deltas on the previous sub buffer do not
1099 add up to be greater than the curre 1045 add up to be greater than the current time stamp.
1100 1046
1101 NOTE: This adds significant overhea 1047 NOTE: This adds significant overhead to recording of events,
1102 and should only be used to test the 1048 and should only be used to test the logic of the ring buffer.
1103 Do not use it on production systems 1049 Do not use it on production systems.
1104 1050
1105 Only say Y if you understand what t 1051 Only say Y if you understand what this does, and you
1106 still want it enabled. Otherwise sa 1052 still want it enabled. Otherwise say N
1107 1053
1108 config MMIOTRACE_TEST 1054 config MMIOTRACE_TEST
1109 tristate "Test module for mmiotrace" 1055 tristate "Test module for mmiotrace"
1110 depends on MMIOTRACE && m 1056 depends on MMIOTRACE && m
1111 help 1057 help
1112 This is a dumb module for testing m 1058 This is a dumb module for testing mmiotrace. It is very dangerous
1113 as it will write garbage to IO memo 1059 as it will write garbage to IO memory starting at a given address.
1114 However, it should be safe to use o 1060 However, it should be safe to use on e.g. unused portion of VRAM.
1115 1061
1116 Say N, unless you absolutely know w 1062 Say N, unless you absolutely know what you are doing.
1117 1063
1118 config PREEMPTIRQ_DELAY_TEST 1064 config PREEMPTIRQ_DELAY_TEST
1119 tristate "Test module to create a pre 1065 tristate "Test module to create a preempt / IRQ disable delay thread to test latency tracers"
1120 depends on m 1066 depends on m
1121 help 1067 help
1122 Select this option to build a test 1068 Select this option to build a test module that can help test latency
1123 tracers by executing a preempt or i 1069 tracers by executing a preempt or irq disable section with a user
1124 configurable delay. The module busy 1070 configurable delay. The module busy waits for the duration of the
1125 critical section. 1071 critical section.
1126 1072
1127 For example, the following invocati 1073 For example, the following invocation generates a burst of three
1128 irq-disabled critical sections for 1074 irq-disabled critical sections for 500us:
1129 modprobe preemptirq_delay_test test 1075 modprobe preemptirq_delay_test test_mode=irq delay=500 burst_size=3
1130 1076
1131 What's more, if you want to attach 1077 What's more, if you want to attach the test on the cpu which the latency
1132 tracer is running on, specify cpu_a 1078 tracer is running on, specify cpu_affinity=cpu_num at the end of the
1133 command. 1079 command.
1134 1080
1135 If unsure, say N 1081 If unsure, say N
1136 1082
1137 config SYNTH_EVENT_GEN_TEST 1083 config SYNTH_EVENT_GEN_TEST
1138 tristate "Test module for in-kernel s 1084 tristate "Test module for in-kernel synthetic event generation"
1139 depends on SYNTH_EVENTS && m !! 1085 depends on SYNTH_EVENTS
1140 help 1086 help
1141 This option creates a test module t 1087 This option creates a test module to check the base
1142 functionality of in-kernel syntheti 1088 functionality of in-kernel synthetic event definition and
1143 generation. 1089 generation.
1144 1090
1145 To test, insert the module, and the 1091 To test, insert the module, and then check the trace buffer
1146 for the generated sample events. 1092 for the generated sample events.
1147 1093
1148 If unsure, say N. 1094 If unsure, say N.
1149 1095
1150 config KPROBE_EVENT_GEN_TEST 1096 config KPROBE_EVENT_GEN_TEST
1151 tristate "Test module for in-kernel k 1097 tristate "Test module for in-kernel kprobe event generation"
1152 depends on KPROBE_EVENTS && m !! 1098 depends on KPROBE_EVENTS
1153 help 1099 help
1154 This option creates a test module t 1100 This option creates a test module to check the base
1155 functionality of in-kernel kprobe e 1101 functionality of in-kernel kprobe event definition.
1156 1102
1157 To test, insert the module, and the 1103 To test, insert the module, and then check the trace buffer
1158 for the generated kprobe events. 1104 for the generated kprobe events.
1159 1105
1160 If unsure, say N. 1106 If unsure, say N.
1161 1107
1162 config HIST_TRIGGERS_DEBUG 1108 config HIST_TRIGGERS_DEBUG
1163 bool "Hist trigger debug support" 1109 bool "Hist trigger debug support"
1164 depends on HIST_TRIGGERS 1110 depends on HIST_TRIGGERS
1165 help 1111 help
1166 Add "hist_debug" file for each even 1112 Add "hist_debug" file for each event, which when read will
1167 dump out a bunch of internal detail 1113 dump out a bunch of internal details about the hist triggers
1168 defined on that event. 1114 defined on that event.
1169 1115
1170 The hist_debug file serves a couple 1116 The hist_debug file serves a couple of purposes:
1171 1117
1172 - Helps developers verify that no 1118 - Helps developers verify that nothing is broken.
1173 1119
1174 - Provides educational informatio 1120 - Provides educational information to support the details
1175 of the hist trigger internals a 1121 of the hist trigger internals as described by
1176 Documentation/trace/histogram-d 1122 Documentation/trace/histogram-design.rst.
1177 1123
1178 The hist_debug output only covers t 1124 The hist_debug output only covers the data structures
1179 related to the histogram definition 1125 related to the histogram definitions themselves and doesn't
1180 display the internals of map bucket 1126 display the internals of map buckets or variable values of
1181 running histograms. 1127 running histograms.
1182 1128
1183 If unsure, say N. 1129 If unsure, say N.
1184 1130
1185 source "kernel/trace/rv/Kconfig" 1131 source "kernel/trace/rv/Kconfig"
1186 1132
1187 endif # FTRACE 1133 endif # FTRACE
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