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1#
2# Architectures that offer an FUNCTION_TRACER implementation should
3# select HAVE_FUNCTION_TRACER:
4#
5
6config USER_STACKTRACE_SUPPORT
7 bool
8
9config NOP_TRACER
10 bool
11
12config HAVE_FTRACE_NMI_ENTER
13 bool
14 help
15 See Documentation/trace/ftrace-design.txt
16
17config HAVE_FUNCTION_TRACER
18 bool
19 help
20 See Documentation/trace/ftrace-design.txt
21
22config HAVE_FUNCTION_GRAPH_TRACER
23 bool
24 help
25 See Documentation/trace/ftrace-design.txt
26
27config HAVE_DYNAMIC_FTRACE
28 bool
29 help
30 See Documentation/trace/ftrace-design.txt
31
32config HAVE_DYNAMIC_FTRACE_WITH_REGS
33 bool
34
35config HAVE_FTRACE_MCOUNT_RECORD
36 bool
37 help
38 See Documentation/trace/ftrace-design.txt
39
40config HAVE_SYSCALL_TRACEPOINTS
41 bool
42 help
43 See Documentation/trace/ftrace-design.txt
44
45config HAVE_FENTRY
46 bool
47 help
48 Arch supports the gcc options -pg with -mfentry
49
50config HAVE_C_RECORDMCOUNT
51 bool
52 help
53 C version of recordmcount available?
54
55config TRACER_MAX_TRACE
56 bool
57
58config TRACE_CLOCK
59 bool
60
61config RING_BUFFER
62 bool
63 select TRACE_CLOCK
64 select IRQ_WORK
65
66config FTRACE_NMI_ENTER
67 bool
68 depends on HAVE_FTRACE_NMI_ENTER
69 default y
70
71config EVENT_TRACING
72 select CONTEXT_SWITCH_TRACER
73 select GLOB
74 bool
75
76config CONTEXT_SWITCH_TRACER
77 bool
78
79config RING_BUFFER_ALLOW_SWAP
80 bool
81 help
82 Allow the use of ring_buffer_swap_cpu.
83 Adds a very slight overhead to tracing when enabled.
84
85# All tracer options should select GENERIC_TRACER. For those options that are
86# enabled by all tracers (context switch and event tracer) they select TRACING.
87# This allows those options to appear when no other tracer is selected. But the
88# options do not appear when something else selects it. We need the two options
89# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
90# hiding of the automatic options.
91
92config TRACING
93 bool
94 select DEBUG_FS
95 select RING_BUFFER
96 select STACKTRACE if STACKTRACE_SUPPORT
97 select TRACEPOINTS
98 select NOP_TRACER
99 select BINARY_PRINTF
100 select EVENT_TRACING
101 select TRACE_CLOCK
102
103config GENERIC_TRACER
104 bool
105 select TRACING
106
107#
108# Minimum requirements an architecture has to meet for us to
109# be able to offer generic tracing facilities:
110#
111config TRACING_SUPPORT
112 bool
113 # PPC32 has no irqflags tracing support, but it can use most of the
114 # tracers anyway, they were tested to build and work. Note that new
115 # exceptions to this list aren't welcomed, better implement the
116 # irqflags tracing for your architecture.
117 depends on TRACE_IRQFLAGS_SUPPORT || PPC32
118 depends on STACKTRACE_SUPPORT
119 default y
120
121if TRACING_SUPPORT
122
123menuconfig FTRACE
124 bool "Tracers"
125 default y if DEBUG_KERNEL
126 help
127 Enable the kernel tracing infrastructure.
128
129if FTRACE
130
131config FUNCTION_TRACER
132 bool "Kernel Function Tracer"
133 depends on HAVE_FUNCTION_TRACER
134 select KALLSYMS
135 select GENERIC_TRACER
136 select CONTEXT_SWITCH_TRACER
137 select GLOB
138 help
139 Enable the kernel to trace every kernel function. This is done
140 by using a compiler feature to insert a small, 5-byte No-Operation
141 instruction at the beginning of every kernel function, which NOP
142 sequence is then dynamically patched into a tracer call when
143 tracing is enabled by the administrator. If it's runtime disabled
144 (the bootup default), then the overhead of the instructions is very
145 small and not measurable even in micro-benchmarks.
146
147config FUNCTION_GRAPH_TRACER
148 bool "Kernel Function Graph Tracer"
149 depends on HAVE_FUNCTION_GRAPH_TRACER
150 depends on FUNCTION_TRACER
151 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
152 default y
153 help
154 Enable the kernel to trace a function at both its return
155 and its entry.
156 Its first purpose is to trace the duration of functions and
157 draw a call graph for each thread with some information like
158 the return value. This is done by setting the current return
159 address on the current task structure into a stack of calls.
160
161
162config IRQSOFF_TRACER
163 bool "Interrupts-off Latency Tracer"
164 default n
165 depends on TRACE_IRQFLAGS_SUPPORT
166 depends on !ARCH_USES_GETTIMEOFFSET
167 select TRACE_IRQFLAGS
168 select GENERIC_TRACER
169 select TRACER_MAX_TRACE
170 select RING_BUFFER_ALLOW_SWAP
171 select TRACER_SNAPSHOT
172 select TRACER_SNAPSHOT_PER_CPU_SWAP
173 help
174 This option measures the time spent in irqs-off critical
175 sections, with microsecond accuracy.
176
177 The default measurement method is a maximum search, which is
178 disabled by default and can be runtime (re-)started
179 via:
180
181 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
182
183 (Note that kernel size and overhead increase with this option
184 enabled. This option and the preempt-off timing option can be
185 used together or separately.)
186
187config PREEMPT_TRACER
188 bool "Preemption-off Latency Tracer"
189 default n
190 depends on !ARCH_USES_GETTIMEOFFSET
191 depends on PREEMPT
192 select GENERIC_TRACER
193 select TRACER_MAX_TRACE
194 select RING_BUFFER_ALLOW_SWAP
195 select TRACER_SNAPSHOT
196 select TRACER_SNAPSHOT_PER_CPU_SWAP
197 help
198 This option measures the time spent in preemption-off critical
199 sections, with microsecond accuracy.
200
201 The default measurement method is a maximum search, which is
202 disabled by default and can be runtime (re-)started
203 via:
204
205 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
206
207 (Note that kernel size and overhead increase with this option
208 enabled. This option and the irqs-off timing option can be
209 used together or separately.)
210
211config SCHED_TRACER
212 bool "Scheduling Latency Tracer"
213 select GENERIC_TRACER
214 select CONTEXT_SWITCH_TRACER
215 select TRACER_MAX_TRACE
216 select TRACER_SNAPSHOT
217 help
218 This tracer tracks the latency of the highest priority task
219 to be scheduled in, starting from the point it has woken up.
220
221config HWLAT_TRACER
222 bool "Tracer to detect hardware latencies (like SMIs)"
223 select GENERIC_TRACER
224 help
225 This tracer, when enabled will create one or more kernel threads,
226 depening on what the cpumask file is set to, which each thread
227 spinning in a loop looking for interruptions caused by
228 something other than the kernel. For example, if a
229 System Management Interrupt (SMI) takes a noticeable amount of
230 time, this tracer will detect it. This is useful for testing
231 if a system is reliable for Real Time tasks.
232
233 Some files are created in the tracing directory when this
234 is enabled:
235
236 hwlat_detector/width - time in usecs for how long to spin for
237 hwlat_detector/window - time in usecs between the start of each
238 iteration
239
240 A kernel thread is created that will spin with interrupts disabled
241 for "width" microseconds in every "widow" cycle. It will not spin
242 for "window - width" microseconds, where the system can
243 continue to operate.
244
245 The output will appear in the trace and trace_pipe files.
246
247 When the tracer is not running, it has no affect on the system,
248 but when it is running, it can cause the system to be
249 periodically non responsive. Do not run this tracer on a
250 production system.
251
252 To enable this tracer, echo in "hwlat" into the current_tracer
253 file. Every time a latency is greater than tracing_thresh, it will
254 be recorded into the ring buffer.
255
256config ENABLE_DEFAULT_TRACERS
257 bool "Trace process context switches and events"
258 depends on !GENERIC_TRACER
259 select TRACING
260 help
261 This tracer hooks to various trace points in the kernel,
262 allowing the user to pick and choose which trace point they
263 want to trace. It also includes the sched_switch tracer plugin.
264
265config FTRACE_SYSCALLS
266 bool "Trace syscalls"
267 depends on HAVE_SYSCALL_TRACEPOINTS
268 select GENERIC_TRACER
269 select KALLSYMS
270 help
271 Basic tracer to catch the syscall entry and exit events.
272
273config TRACER_SNAPSHOT
274 bool "Create a snapshot trace buffer"
275 select TRACER_MAX_TRACE
276 help
277 Allow tracing users to take snapshot of the current buffer using the
278 ftrace interface, e.g.:
279
280 echo 1 > /sys/kernel/debug/tracing/snapshot
281 cat snapshot
282
283config TRACER_SNAPSHOT_PER_CPU_SWAP
284 bool "Allow snapshot to swap per CPU"
285 depends on TRACER_SNAPSHOT
286 select RING_BUFFER_ALLOW_SWAP
287 help
288 Allow doing a snapshot of a single CPU buffer instead of a
289 full swap (all buffers). If this is set, then the following is
290 allowed:
291
292 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
293
294 After which, only the tracing buffer for CPU 2 was swapped with
295 the main tracing buffer, and the other CPU buffers remain the same.
296
297 When this is enabled, this adds a little more overhead to the
298 trace recording, as it needs to add some checks to synchronize
299 recording with swaps. But this does not affect the performance
300 of the overall system. This is enabled by default when the preempt
301 or irq latency tracers are enabled, as those need to swap as well
302 and already adds the overhead (plus a lot more).
303
304config TRACE_BRANCH_PROFILING
305 bool
306 select GENERIC_TRACER
307
308choice
309 prompt "Branch Profiling"
310 default BRANCH_PROFILE_NONE
311 help
312 The branch profiling is a software profiler. It will add hooks
313 into the C conditionals to test which path a branch takes.
314
315 The likely/unlikely profiler only looks at the conditions that
316 are annotated with a likely or unlikely macro.
317
318 The "all branch" profiler will profile every if-statement in the
319 kernel. This profiler will also enable the likely/unlikely
320 profiler.
321
322 Either of the above profilers adds a bit of overhead to the system.
323 If unsure, choose "No branch profiling".
324
325config BRANCH_PROFILE_NONE
326 bool "No branch profiling"
327 help
328 No branch profiling. Branch profiling adds a bit of overhead.
329 Only enable it if you want to analyse the branching behavior.
330 Otherwise keep it disabled.
331
332config PROFILE_ANNOTATED_BRANCHES
333 bool "Trace likely/unlikely profiler"
334 select TRACE_BRANCH_PROFILING
335 help
336 This tracer profiles all likely and unlikely macros
337 in the kernel. It will display the results in:
338
339 /sys/kernel/debug/tracing/trace_stat/branch_annotated
340
341 Note: this will add a significant overhead; only turn this
342 on if you need to profile the system's use of these macros.
343
344config PROFILE_ALL_BRANCHES
345 bool "Profile all if conditionals"
346 select TRACE_BRANCH_PROFILING
347 help
348 This tracer profiles all branch conditions. Every if ()
349 taken in the kernel is recorded whether it hit or miss.
350 The results will be displayed in:
351
352 /sys/kernel/debug/tracing/trace_stat/branch_all
353
354 This option also enables the likely/unlikely profiler.
355
356 This configuration, when enabled, will impose a great overhead
357 on the system. This should only be enabled when the system
358 is to be analyzed in much detail.
359endchoice
360
361config TRACING_BRANCHES
362 bool
363 help
364 Selected by tracers that will trace the likely and unlikely
365 conditions. This prevents the tracers themselves from being
366 profiled. Profiling the tracing infrastructure can only happen
367 when the likelys and unlikelys are not being traced.
368
369config BRANCH_TRACER
370 bool "Trace likely/unlikely instances"
371 depends on TRACE_BRANCH_PROFILING
372 select TRACING_BRANCHES
373 help
374 This traces the events of likely and unlikely condition
375 calls in the kernel. The difference between this and the
376 "Trace likely/unlikely profiler" is that this is not a
377 histogram of the callers, but actually places the calling
378 events into a running trace buffer to see when and where the
379 events happened, as well as their results.
380
381 Say N if unsure.
382
383config STACK_TRACER
384 bool "Trace max stack"
385 depends on HAVE_FUNCTION_TRACER
386 select FUNCTION_TRACER
387 select STACKTRACE
388 select KALLSYMS
389 help
390 This special tracer records the maximum stack footprint of the
391 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
392
393 This tracer works by hooking into every function call that the
394 kernel executes, and keeping a maximum stack depth value and
395 stack-trace saved. If this is configured with DYNAMIC_FTRACE
396 then it will not have any overhead while the stack tracer
397 is disabled.
398
399 To enable the stack tracer on bootup, pass in 'stacktrace'
400 on the kernel command line.
401
402 The stack tracer can also be enabled or disabled via the
403 sysctl kernel.stack_tracer_enabled
404
405 Say N if unsure.
406
407config BLK_DEV_IO_TRACE
408 bool "Support for tracing block IO actions"
409 depends on SYSFS
410 depends on BLOCK
411 select RELAY
412 select DEBUG_FS
413 select TRACEPOINTS
414 select GENERIC_TRACER
415 select STACKTRACE
416 help
417 Say Y here if you want to be able to trace the block layer actions
418 on a given queue. Tracing allows you to see any traffic happening
419 on a block device queue. For more information (and the userspace
420 support tools needed), fetch the blktrace tools from:
421
422 git://git.kernel.dk/blktrace.git
423
424 Tracing also is possible using the ftrace interface, e.g.:
425
426 echo 1 > /sys/block/sda/sda1/trace/enable
427 echo blk > /sys/kernel/debug/tracing/current_tracer
428 cat /sys/kernel/debug/tracing/trace_pipe
429
430 If unsure, say N.
431
432config KPROBE_EVENT
433 depends on KPROBES
434 depends on HAVE_REGS_AND_STACK_ACCESS_API
435 bool "Enable kprobes-based dynamic events"
436 select TRACING
437 select PROBE_EVENTS
438 default y
439 help
440 This allows the user to add tracing events (similar to tracepoints)
441 on the fly via the ftrace interface. See
442 Documentation/trace/kprobetrace.txt for more details.
443
444 Those events can be inserted wherever kprobes can probe, and record
445 various register and memory values.
446
447 This option is also required by perf-probe subcommand of perf tools.
448 If you want to use perf tools, this option is strongly recommended.
449
450config UPROBE_EVENT
451 bool "Enable uprobes-based dynamic events"
452 depends on ARCH_SUPPORTS_UPROBES
453 depends on MMU
454 depends on PERF_EVENTS
455 select UPROBES
456 select PROBE_EVENTS
457 select TRACING
458 default n
459 help
460 This allows the user to add tracing events on top of userspace
461 dynamic events (similar to tracepoints) on the fly via the trace
462 events interface. Those events can be inserted wherever uprobes
463 can probe, and record various registers.
464 This option is required if you plan to use perf-probe subcommand
465 of perf tools on user space applications.
466
467config BPF_EVENTS
468 depends on BPF_SYSCALL
469 depends on (KPROBE_EVENT || UPROBE_EVENT) && PERF_EVENTS
470 bool
471 default y
472 help
473 This allows the user to attach BPF programs to kprobe events.
474
475config PROBE_EVENTS
476 def_bool n
477
478config DYNAMIC_FTRACE
479 bool "enable/disable function tracing dynamically"
480 depends on FUNCTION_TRACER
481 depends on HAVE_DYNAMIC_FTRACE
482 default y
483 help
484 This option will modify all the calls to function tracing
485 dynamically (will patch them out of the binary image and
486 replace them with a No-Op instruction) on boot up. During
487 compile time, a table is made of all the locations that ftrace
488 can function trace, and this table is linked into the kernel
489 image. When this is enabled, functions can be individually
490 enabled, and the functions not enabled will not affect
491 performance of the system.
492
493 See the files in /sys/kernel/debug/tracing:
494 available_filter_functions
495 set_ftrace_filter
496 set_ftrace_notrace
497
498 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
499 otherwise has native performance as long as no tracing is active.
500
501config DYNAMIC_FTRACE_WITH_REGS
502 def_bool y
503 depends on DYNAMIC_FTRACE
504 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
505
506config FUNCTION_PROFILER
507 bool "Kernel function profiler"
508 depends on FUNCTION_TRACER
509 default n
510 help
511 This option enables the kernel function profiler. A file is created
512 in debugfs called function_profile_enabled which defaults to zero.
513 When a 1 is echoed into this file profiling begins, and when a
514 zero is entered, profiling stops. A "functions" file is created in
515 the trace_stats directory; this file shows the list of functions that
516 have been hit and their counters.
517
518 If in doubt, say N.
519
520config FTRACE_MCOUNT_RECORD
521 def_bool y
522 depends on DYNAMIC_FTRACE
523 depends on HAVE_FTRACE_MCOUNT_RECORD
524
525config FTRACE_SELFTEST
526 bool
527
528config FTRACE_STARTUP_TEST
529 bool "Perform a startup test on ftrace"
530 depends on GENERIC_TRACER
531 select FTRACE_SELFTEST
532 help
533 This option performs a series of startup tests on ftrace. On bootup
534 a series of tests are made to verify that the tracer is
535 functioning properly. It will do tests on all the configured
536 tracers of ftrace.
537
538config EVENT_TRACE_TEST_SYSCALLS
539 bool "Run selftest on syscall events"
540 depends on FTRACE_STARTUP_TEST
541 help
542 This option will also enable testing every syscall event.
543 It only enables the event and disables it and runs various loads
544 with the event enabled. This adds a bit more time for kernel boot
545 up since it runs this on every system call defined.
546
547 TBD - enable a way to actually call the syscalls as we test their
548 events
549
550config MMIOTRACE
551 bool "Memory mapped IO tracing"
552 depends on HAVE_MMIOTRACE_SUPPORT && PCI
553 select GENERIC_TRACER
554 help
555 Mmiotrace traces Memory Mapped I/O access and is meant for
556 debugging and reverse engineering. It is called from the ioremap
557 implementation and works via page faults. Tracing is disabled by
558 default and can be enabled at run-time.
559
560 See Documentation/trace/mmiotrace.txt.
561 If you are not helping to develop drivers, say N.
562
563config TRACING_MAP
564 bool
565 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
566 help
567 tracing_map is a special-purpose lock-free map for tracing,
568 separated out as a stand-alone facility in order to allow it
569 to be shared between multiple tracers. It isn't meant to be
570 generally used outside of that context, and is normally
571 selected by tracers that use it.
572
573config HIST_TRIGGERS
574 bool "Histogram triggers"
575 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
576 select TRACING_MAP
577 select TRACING
578 default n
579 help
580 Hist triggers allow one or more arbitrary trace event fields
581 to be aggregated into hash tables and dumped to stdout by
582 reading a debugfs/tracefs file. They're useful for
583 gathering quick and dirty (though precise) summaries of
584 event activity as an initial guide for further investigation
585 using more advanced tools.
586
587 See Documentation/trace/events.txt.
588 If in doubt, say N.
589
590config MMIOTRACE_TEST
591 tristate "Test module for mmiotrace"
592 depends on MMIOTRACE && m
593 help
594 This is a dumb module for testing mmiotrace. It is very dangerous
595 as it will write garbage to IO memory starting at a given address.
596 However, it should be safe to use on e.g. unused portion of VRAM.
597
598 Say N, unless you absolutely know what you are doing.
599
600config TRACEPOINT_BENCHMARK
601 bool "Add tracepoint that benchmarks tracepoints"
602 help
603 This option creates the tracepoint "benchmark:benchmark_event".
604 When the tracepoint is enabled, it kicks off a kernel thread that
605 goes into an infinite loop (calling cond_sched() to let other tasks
606 run), and calls the tracepoint. Each iteration will record the time
607 it took to write to the tracepoint and the next iteration that
608 data will be passed to the tracepoint itself. That is, the tracepoint
609 will report the time it took to do the previous tracepoint.
610 The string written to the tracepoint is a static string of 128 bytes
611 to keep the time the same. The initial string is simply a write of
612 "START". The second string records the cold cache time of the first
613 write which is not added to the rest of the calculations.
614
615 As it is a tight loop, it benchmarks as hot cache. That's fine because
616 we care most about hot paths that are probably in cache already.
617
618 An example of the output:
619
620 START
621 first=3672 [COLD CACHED]
622 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
623 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
624 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
625 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
626 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
627 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
628
629
630config RING_BUFFER_BENCHMARK
631 tristate "Ring buffer benchmark stress tester"
632 depends on RING_BUFFER
633 help
634 This option creates a test to stress the ring buffer and benchmark it.
635 It creates its own ring buffer such that it will not interfere with
636 any other users of the ring buffer (such as ftrace). It then creates
637 a producer and consumer that will run for 10 seconds and sleep for
638 10 seconds. Each interval it will print out the number of events
639 it recorded and give a rough estimate of how long each iteration took.
640
641 It does not disable interrupts or raise its priority, so it may be
642 affected by processes that are running.
643
644 If unsure, say N.
645
646config RING_BUFFER_STARTUP_TEST
647 bool "Ring buffer startup self test"
648 depends on RING_BUFFER
649 help
650 Run a simple self test on the ring buffer on boot up. Late in the
651 kernel boot sequence, the test will start that kicks off
652 a thread per cpu. Each thread will write various size events
653 into the ring buffer. Another thread is created to send IPIs
654 to each of the threads, where the IPI handler will also write
655 to the ring buffer, to test/stress the nesting ability.
656 If any anomalies are discovered, a warning will be displayed
657 and all ring buffers will be disabled.
658
659 The test runs for 10 seconds. This will slow your boot time
660 by at least 10 more seconds.
661
662 At the end of the test, statics and more checks are done.
663 It will output the stats of each per cpu buffer. What
664 was written, the sizes, what was read, what was lost, and
665 other similar details.
666
667 If unsure, say N
668
669config TRACE_ENUM_MAP_FILE
670 bool "Show enum mappings for trace events"
671 depends on TRACING
672 help
673 The "print fmt" of the trace events will show the enum names instead
674 of their values. This can cause problems for user space tools that
675 use this string to parse the raw data as user space does not know
676 how to convert the string to its value.
677
678 To fix this, there's a special macro in the kernel that can be used
679 to convert the enum into its value. If this macro is used, then the
680 print fmt strings will have the enums converted to their values.
681
682 If something does not get converted properly, this option can be
683 used to show what enums the kernel tried to convert.
684
685 This option is for debugging the enum conversions. A file is created
686 in the tracing directory called "enum_map" that will show the enum
687 names matched with their values and what trace event system they
688 belong too.
689
690 Normally, the mapping of the strings to values will be freed after
691 boot up or module load. With this option, they will not be freed, as
692 they are needed for the "enum_map" file. Enabling this option will
693 increase the memory footprint of the running kernel.
694
695 If unsure, say N
696
697config TRACING_EVENTS_GPIO
698 bool "Trace gpio events"
699 depends on GPIOLIB
700 default y
701 help
702 Enable tracing events for gpio subsystem
703
704endif # FTRACE
705
706endif # TRACING_SUPPORT
707
1# SPDX-License-Identifier: GPL-2.0-only
2#
3# Architectures that offer an FUNCTION_TRACER implementation should
4# select HAVE_FUNCTION_TRACER:
5#
6
7config USER_STACKTRACE_SUPPORT
8 bool
9
10config NOP_TRACER
11 bool
12
13config HAVE_FTRACE_NMI_ENTER
14 bool
15 help
16 See Documentation/trace/ftrace-design.rst
17
18config HAVE_FUNCTION_TRACER
19 bool
20 help
21 See Documentation/trace/ftrace-design.rst
22
23config HAVE_FUNCTION_GRAPH_TRACER
24 bool
25 help
26 See Documentation/trace/ftrace-design.rst
27
28config HAVE_DYNAMIC_FTRACE
29 bool
30 help
31 See Documentation/trace/ftrace-design.rst
32
33config HAVE_DYNAMIC_FTRACE_WITH_REGS
34 bool
35
36config HAVE_FTRACE_MCOUNT_RECORD
37 bool
38 help
39 See Documentation/trace/ftrace-design.rst
40
41config HAVE_SYSCALL_TRACEPOINTS
42 bool
43 help
44 See Documentation/trace/ftrace-design.rst
45
46config HAVE_FENTRY
47 bool
48 help
49 Arch supports the gcc options -pg with -mfentry
50
51config HAVE_NOP_MCOUNT
52 bool
53 help
54 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
55
56config HAVE_C_RECORDMCOUNT
57 bool
58 help
59 C version of recordmcount available?
60
61config TRACER_MAX_TRACE
62 bool
63
64config TRACE_CLOCK
65 bool
66
67config RING_BUFFER
68 bool
69 select TRACE_CLOCK
70 select IRQ_WORK
71
72config FTRACE_NMI_ENTER
73 bool
74 depends on HAVE_FTRACE_NMI_ENTER
75 default y
76
77config EVENT_TRACING
78 select CONTEXT_SWITCH_TRACER
79 select GLOB
80 bool
81
82config CONTEXT_SWITCH_TRACER
83 bool
84
85config RING_BUFFER_ALLOW_SWAP
86 bool
87 help
88 Allow the use of ring_buffer_swap_cpu.
89 Adds a very slight overhead to tracing when enabled.
90
91config PREEMPTIRQ_TRACEPOINTS
92 bool
93 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
94 select TRACING
95 default y
96 help
97 Create preempt/irq toggle tracepoints if needed, so that other parts
98 of the kernel can use them to generate or add hooks to them.
99
100# All tracer options should select GENERIC_TRACER. For those options that are
101# enabled by all tracers (context switch and event tracer) they select TRACING.
102# This allows those options to appear when no other tracer is selected. But the
103# options do not appear when something else selects it. We need the two options
104# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
105# hiding of the automatic options.
106
107config TRACING
108 bool
109 select DEBUG_FS
110 select RING_BUFFER
111 select STACKTRACE if STACKTRACE_SUPPORT
112 select TRACEPOINTS
113 select NOP_TRACER
114 select BINARY_PRINTF
115 select EVENT_TRACING
116 select TRACE_CLOCK
117
118config GENERIC_TRACER
119 bool
120 select TRACING
121
122#
123# Minimum requirements an architecture has to meet for us to
124# be able to offer generic tracing facilities:
125#
126config TRACING_SUPPORT
127 bool
128 depends on TRACE_IRQFLAGS_SUPPORT
129 depends on STACKTRACE_SUPPORT
130 default y
131
132if TRACING_SUPPORT
133
134menuconfig FTRACE
135 bool "Tracers"
136 default y if DEBUG_KERNEL
137 help
138 Enable the kernel tracing infrastructure.
139
140if FTRACE
141
142config FUNCTION_TRACER
143 bool "Kernel Function Tracer"
144 depends on HAVE_FUNCTION_TRACER
145 select KALLSYMS
146 select GENERIC_TRACER
147 select CONTEXT_SWITCH_TRACER
148 select GLOB
149 select TASKS_RCU if PREEMPTION
150 help
151 Enable the kernel to trace every kernel function. This is done
152 by using a compiler feature to insert a small, 5-byte No-Operation
153 instruction at the beginning of every kernel function, which NOP
154 sequence is then dynamically patched into a tracer call when
155 tracing is enabled by the administrator. If it's runtime disabled
156 (the bootup default), then the overhead of the instructions is very
157 small and not measurable even in micro-benchmarks.
158
159config FUNCTION_GRAPH_TRACER
160 bool "Kernel Function Graph Tracer"
161 depends on HAVE_FUNCTION_GRAPH_TRACER
162 depends on FUNCTION_TRACER
163 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
164 default y
165 help
166 Enable the kernel to trace a function at both its return
167 and its entry.
168 Its first purpose is to trace the duration of functions and
169 draw a call graph for each thread with some information like
170 the return value. This is done by setting the current return
171 address on the current task structure into a stack of calls.
172
173config TRACE_PREEMPT_TOGGLE
174 bool
175 help
176 Enables hooks which will be called when preemption is first disabled,
177 and last enabled.
178
179config PREEMPTIRQ_EVENTS
180 bool "Enable trace events for preempt and irq disable/enable"
181 select TRACE_IRQFLAGS
182 select TRACE_PREEMPT_TOGGLE if PREEMPTION
183 select GENERIC_TRACER
184 default n
185 help
186 Enable tracing of disable and enable events for preemption and irqs.
187
188config IRQSOFF_TRACER
189 bool "Interrupts-off Latency Tracer"
190 default n
191 depends on TRACE_IRQFLAGS_SUPPORT
192 depends on !ARCH_USES_GETTIMEOFFSET
193 select TRACE_IRQFLAGS
194 select GENERIC_TRACER
195 select TRACER_MAX_TRACE
196 select RING_BUFFER_ALLOW_SWAP
197 select TRACER_SNAPSHOT
198 select TRACER_SNAPSHOT_PER_CPU_SWAP
199 help
200 This option measures the time spent in irqs-off critical
201 sections, with microsecond accuracy.
202
203 The default measurement method is a maximum search, which is
204 disabled by default and can be runtime (re-)started
205 via:
206
207 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
208
209 (Note that kernel size and overhead increase with this option
210 enabled. This option and the preempt-off timing option can be
211 used together or separately.)
212
213config PREEMPT_TRACER
214 bool "Preemption-off Latency Tracer"
215 default n
216 depends on !ARCH_USES_GETTIMEOFFSET
217 depends on PREEMPTION
218 select GENERIC_TRACER
219 select TRACER_MAX_TRACE
220 select RING_BUFFER_ALLOW_SWAP
221 select TRACER_SNAPSHOT
222 select TRACER_SNAPSHOT_PER_CPU_SWAP
223 select TRACE_PREEMPT_TOGGLE
224 help
225 This option measures the time spent in preemption-off critical
226 sections, with microsecond accuracy.
227
228 The default measurement method is a maximum search, which is
229 disabled by default and can be runtime (re-)started
230 via:
231
232 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
233
234 (Note that kernel size and overhead increase with this option
235 enabled. This option and the irqs-off timing option can be
236 used together or separately.)
237
238config SCHED_TRACER
239 bool "Scheduling Latency Tracer"
240 select GENERIC_TRACER
241 select CONTEXT_SWITCH_TRACER
242 select TRACER_MAX_TRACE
243 select TRACER_SNAPSHOT
244 help
245 This tracer tracks the latency of the highest priority task
246 to be scheduled in, starting from the point it has woken up.
247
248config HWLAT_TRACER
249 bool "Tracer to detect hardware latencies (like SMIs)"
250 select GENERIC_TRACER
251 help
252 This tracer, when enabled will create one or more kernel threads,
253 depending on what the cpumask file is set to, which each thread
254 spinning in a loop looking for interruptions caused by
255 something other than the kernel. For example, if a
256 System Management Interrupt (SMI) takes a noticeable amount of
257 time, this tracer will detect it. This is useful for testing
258 if a system is reliable for Real Time tasks.
259
260 Some files are created in the tracing directory when this
261 is enabled:
262
263 hwlat_detector/width - time in usecs for how long to spin for
264 hwlat_detector/window - time in usecs between the start of each
265 iteration
266
267 A kernel thread is created that will spin with interrupts disabled
268 for "width" microseconds in every "window" cycle. It will not spin
269 for "window - width" microseconds, where the system can
270 continue to operate.
271
272 The output will appear in the trace and trace_pipe files.
273
274 When the tracer is not running, it has no affect on the system,
275 but when it is running, it can cause the system to be
276 periodically non responsive. Do not run this tracer on a
277 production system.
278
279 To enable this tracer, echo in "hwlat" into the current_tracer
280 file. Every time a latency is greater than tracing_thresh, it will
281 be recorded into the ring buffer.
282
283config ENABLE_DEFAULT_TRACERS
284 bool "Trace process context switches and events"
285 depends on !GENERIC_TRACER
286 select TRACING
287 help
288 This tracer hooks to various trace points in the kernel,
289 allowing the user to pick and choose which trace point they
290 want to trace. It also includes the sched_switch tracer plugin.
291
292config FTRACE_SYSCALLS
293 bool "Trace syscalls"
294 depends on HAVE_SYSCALL_TRACEPOINTS
295 select GENERIC_TRACER
296 select KALLSYMS
297 help
298 Basic tracer to catch the syscall entry and exit events.
299
300config TRACER_SNAPSHOT
301 bool "Create a snapshot trace buffer"
302 select TRACER_MAX_TRACE
303 help
304 Allow tracing users to take snapshot of the current buffer using the
305 ftrace interface, e.g.:
306
307 echo 1 > /sys/kernel/debug/tracing/snapshot
308 cat snapshot
309
310config TRACER_SNAPSHOT_PER_CPU_SWAP
311 bool "Allow snapshot to swap per CPU"
312 depends on TRACER_SNAPSHOT
313 select RING_BUFFER_ALLOW_SWAP
314 help
315 Allow doing a snapshot of a single CPU buffer instead of a
316 full swap (all buffers). If this is set, then the following is
317 allowed:
318
319 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
320
321 After which, only the tracing buffer for CPU 2 was swapped with
322 the main tracing buffer, and the other CPU buffers remain the same.
323
324 When this is enabled, this adds a little more overhead to the
325 trace recording, as it needs to add some checks to synchronize
326 recording with swaps. But this does not affect the performance
327 of the overall system. This is enabled by default when the preempt
328 or irq latency tracers are enabled, as those need to swap as well
329 and already adds the overhead (plus a lot more).
330
331config TRACE_BRANCH_PROFILING
332 bool
333 select GENERIC_TRACER
334
335choice
336 prompt "Branch Profiling"
337 default BRANCH_PROFILE_NONE
338 help
339 The branch profiling is a software profiler. It will add hooks
340 into the C conditionals to test which path a branch takes.
341
342 The likely/unlikely profiler only looks at the conditions that
343 are annotated with a likely or unlikely macro.
344
345 The "all branch" profiler will profile every if-statement in the
346 kernel. This profiler will also enable the likely/unlikely
347 profiler.
348
349 Either of the above profilers adds a bit of overhead to the system.
350 If unsure, choose "No branch profiling".
351
352config BRANCH_PROFILE_NONE
353 bool "No branch profiling"
354 help
355 No branch profiling. Branch profiling adds a bit of overhead.
356 Only enable it if you want to analyse the branching behavior.
357 Otherwise keep it disabled.
358
359config PROFILE_ANNOTATED_BRANCHES
360 bool "Trace likely/unlikely profiler"
361 select TRACE_BRANCH_PROFILING
362 help
363 This tracer profiles all likely and unlikely macros
364 in the kernel. It will display the results in:
365
366 /sys/kernel/debug/tracing/trace_stat/branch_annotated
367
368 Note: this will add a significant overhead; only turn this
369 on if you need to profile the system's use of these macros.
370
371config PROFILE_ALL_BRANCHES
372 bool "Profile all if conditionals" if !FORTIFY_SOURCE
373 select TRACE_BRANCH_PROFILING
374 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
375 help
376 This tracer profiles all branch conditions. Every if ()
377 taken in the kernel is recorded whether it hit or miss.
378 The results will be displayed in:
379
380 /sys/kernel/debug/tracing/trace_stat/branch_all
381
382 This option also enables the likely/unlikely profiler.
383
384 This configuration, when enabled, will impose a great overhead
385 on the system. This should only be enabled when the system
386 is to be analyzed in much detail.
387endchoice
388
389config TRACING_BRANCHES
390 bool
391 help
392 Selected by tracers that will trace the likely and unlikely
393 conditions. This prevents the tracers themselves from being
394 profiled. Profiling the tracing infrastructure can only happen
395 when the likelys and unlikelys are not being traced.
396
397config BRANCH_TRACER
398 bool "Trace likely/unlikely instances"
399 depends on TRACE_BRANCH_PROFILING
400 select TRACING_BRANCHES
401 help
402 This traces the events of likely and unlikely condition
403 calls in the kernel. The difference between this and the
404 "Trace likely/unlikely profiler" is that this is not a
405 histogram of the callers, but actually places the calling
406 events into a running trace buffer to see when and where the
407 events happened, as well as their results.
408
409 Say N if unsure.
410
411config STACK_TRACER
412 bool "Trace max stack"
413 depends on HAVE_FUNCTION_TRACER
414 select FUNCTION_TRACER
415 select STACKTRACE
416 select KALLSYMS
417 help
418 This special tracer records the maximum stack footprint of the
419 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
420
421 This tracer works by hooking into every function call that the
422 kernel executes, and keeping a maximum stack depth value and
423 stack-trace saved. If this is configured with DYNAMIC_FTRACE
424 then it will not have any overhead while the stack tracer
425 is disabled.
426
427 To enable the stack tracer on bootup, pass in 'stacktrace'
428 on the kernel command line.
429
430 The stack tracer can also be enabled or disabled via the
431 sysctl kernel.stack_tracer_enabled
432
433 Say N if unsure.
434
435config BLK_DEV_IO_TRACE
436 bool "Support for tracing block IO actions"
437 depends on SYSFS
438 depends on BLOCK
439 select RELAY
440 select DEBUG_FS
441 select TRACEPOINTS
442 select GENERIC_TRACER
443 select STACKTRACE
444 help
445 Say Y here if you want to be able to trace the block layer actions
446 on a given queue. Tracing allows you to see any traffic happening
447 on a block device queue. For more information (and the userspace
448 support tools needed), fetch the blktrace tools from:
449
450 git://git.kernel.dk/blktrace.git
451
452 Tracing also is possible using the ftrace interface, e.g.:
453
454 echo 1 > /sys/block/sda/sda1/trace/enable
455 echo blk > /sys/kernel/debug/tracing/current_tracer
456 cat /sys/kernel/debug/tracing/trace_pipe
457
458 If unsure, say N.
459
460config KPROBE_EVENTS
461 depends on KPROBES
462 depends on HAVE_REGS_AND_STACK_ACCESS_API
463 bool "Enable kprobes-based dynamic events"
464 select TRACING
465 select PROBE_EVENTS
466 select DYNAMIC_EVENTS
467 default y
468 help
469 This allows the user to add tracing events (similar to tracepoints)
470 on the fly via the ftrace interface. See
471 Documentation/trace/kprobetrace.rst for more details.
472
473 Those events can be inserted wherever kprobes can probe, and record
474 various register and memory values.
475
476 This option is also required by perf-probe subcommand of perf tools.
477 If you want to use perf tools, this option is strongly recommended.
478
479config KPROBE_EVENTS_ON_NOTRACE
480 bool "Do NOT protect notrace function from kprobe events"
481 depends on KPROBE_EVENTS
482 depends on KPROBES_ON_FTRACE
483 default n
484 help
485 This is only for the developers who want to debug ftrace itself
486 using kprobe events.
487
488 If kprobes can use ftrace instead of breakpoint, ftrace related
489 functions are protected from kprobe-events to prevent an infinit
490 recursion or any unexpected execution path which leads to a kernel
491 crash.
492
493 This option disables such protection and allows you to put kprobe
494 events on ftrace functions for debugging ftrace by itself.
495 Note that this might let you shoot yourself in the foot.
496
497 If unsure, say N.
498
499config UPROBE_EVENTS
500 bool "Enable uprobes-based dynamic events"
501 depends on ARCH_SUPPORTS_UPROBES
502 depends on MMU
503 depends on PERF_EVENTS
504 select UPROBES
505 select PROBE_EVENTS
506 select DYNAMIC_EVENTS
507 select TRACING
508 default y
509 help
510 This allows the user to add tracing events on top of userspace
511 dynamic events (similar to tracepoints) on the fly via the trace
512 events interface. Those events can be inserted wherever uprobes
513 can probe, and record various registers.
514 This option is required if you plan to use perf-probe subcommand
515 of perf tools on user space applications.
516
517config BPF_EVENTS
518 depends on BPF_SYSCALL
519 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
520 bool
521 default y
522 help
523 This allows the user to attach BPF programs to kprobe, uprobe, and
524 tracepoint events.
525
526config DYNAMIC_EVENTS
527 def_bool n
528
529config PROBE_EVENTS
530 def_bool n
531
532config DYNAMIC_FTRACE
533 bool "enable/disable function tracing dynamically"
534 depends on FUNCTION_TRACER
535 depends on HAVE_DYNAMIC_FTRACE
536 default y
537 help
538 This option will modify all the calls to function tracing
539 dynamically (will patch them out of the binary image and
540 replace them with a No-Op instruction) on boot up. During
541 compile time, a table is made of all the locations that ftrace
542 can function trace, and this table is linked into the kernel
543 image. When this is enabled, functions can be individually
544 enabled, and the functions not enabled will not affect
545 performance of the system.
546
547 See the files in /sys/kernel/debug/tracing:
548 available_filter_functions
549 set_ftrace_filter
550 set_ftrace_notrace
551
552 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
553 otherwise has native performance as long as no tracing is active.
554
555config DYNAMIC_FTRACE_WITH_REGS
556 def_bool y
557 depends on DYNAMIC_FTRACE
558 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
559
560config FUNCTION_PROFILER
561 bool "Kernel function profiler"
562 depends on FUNCTION_TRACER
563 default n
564 help
565 This option enables the kernel function profiler. A file is created
566 in debugfs called function_profile_enabled which defaults to zero.
567 When a 1 is echoed into this file profiling begins, and when a
568 zero is entered, profiling stops. A "functions" file is created in
569 the trace_stat directory; this file shows the list of functions that
570 have been hit and their counters.
571
572 If in doubt, say N.
573
574config BPF_KPROBE_OVERRIDE
575 bool "Enable BPF programs to override a kprobed function"
576 depends on BPF_EVENTS
577 depends on FUNCTION_ERROR_INJECTION
578 default n
579 help
580 Allows BPF to override the execution of a probed function and
581 set a different return value. This is used for error injection.
582
583config FTRACE_MCOUNT_RECORD
584 def_bool y
585 depends on DYNAMIC_FTRACE
586 depends on HAVE_FTRACE_MCOUNT_RECORD
587
588config FTRACE_SELFTEST
589 bool
590
591config FTRACE_STARTUP_TEST
592 bool "Perform a startup test on ftrace"
593 depends on GENERIC_TRACER
594 select FTRACE_SELFTEST
595 help
596 This option performs a series of startup tests on ftrace. On bootup
597 a series of tests are made to verify that the tracer is
598 functioning properly. It will do tests on all the configured
599 tracers of ftrace.
600
601config EVENT_TRACE_STARTUP_TEST
602 bool "Run selftest on trace events"
603 depends on FTRACE_STARTUP_TEST
604 default y
605 help
606 This option performs a test on all trace events in the system.
607 It basically just enables each event and runs some code that
608 will trigger events (not necessarily the event it enables)
609 This may take some time run as there are a lot of events.
610
611config EVENT_TRACE_TEST_SYSCALLS
612 bool "Run selftest on syscall events"
613 depends on EVENT_TRACE_STARTUP_TEST
614 help
615 This option will also enable testing every syscall event.
616 It only enables the event and disables it and runs various loads
617 with the event enabled. This adds a bit more time for kernel boot
618 up since it runs this on every system call defined.
619
620 TBD - enable a way to actually call the syscalls as we test their
621 events
622
623config MMIOTRACE
624 bool "Memory mapped IO tracing"
625 depends on HAVE_MMIOTRACE_SUPPORT && PCI
626 select GENERIC_TRACER
627 help
628 Mmiotrace traces Memory Mapped I/O access and is meant for
629 debugging and reverse engineering. It is called from the ioremap
630 implementation and works via page faults. Tracing is disabled by
631 default and can be enabled at run-time.
632
633 See Documentation/trace/mmiotrace.rst.
634 If you are not helping to develop drivers, say N.
635
636config TRACING_MAP
637 bool
638 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
639 help
640 tracing_map is a special-purpose lock-free map for tracing,
641 separated out as a stand-alone facility in order to allow it
642 to be shared between multiple tracers. It isn't meant to be
643 generally used outside of that context, and is normally
644 selected by tracers that use it.
645
646config HIST_TRIGGERS
647 bool "Histogram triggers"
648 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
649 select TRACING_MAP
650 select TRACING
651 select DYNAMIC_EVENTS
652 default n
653 help
654 Hist triggers allow one or more arbitrary trace event fields
655 to be aggregated into hash tables and dumped to stdout by
656 reading a debugfs/tracefs file. They're useful for
657 gathering quick and dirty (though precise) summaries of
658 event activity as an initial guide for further investigation
659 using more advanced tools.
660
661 Inter-event tracing of quantities such as latencies is also
662 supported using hist triggers under this option.
663
664 See Documentation/trace/histogram.rst.
665 If in doubt, say N.
666
667config MMIOTRACE_TEST
668 tristate "Test module for mmiotrace"
669 depends on MMIOTRACE && m
670 help
671 This is a dumb module for testing mmiotrace. It is very dangerous
672 as it will write garbage to IO memory starting at a given address.
673 However, it should be safe to use on e.g. unused portion of VRAM.
674
675 Say N, unless you absolutely know what you are doing.
676
677config TRACEPOINT_BENCHMARK
678 bool "Add tracepoint that benchmarks tracepoints"
679 help
680 This option creates the tracepoint "benchmark:benchmark_event".
681 When the tracepoint is enabled, it kicks off a kernel thread that
682 goes into an infinite loop (calling cond_sched() to let other tasks
683 run), and calls the tracepoint. Each iteration will record the time
684 it took to write to the tracepoint and the next iteration that
685 data will be passed to the tracepoint itself. That is, the tracepoint
686 will report the time it took to do the previous tracepoint.
687 The string written to the tracepoint is a static string of 128 bytes
688 to keep the time the same. The initial string is simply a write of
689 "START". The second string records the cold cache time of the first
690 write which is not added to the rest of the calculations.
691
692 As it is a tight loop, it benchmarks as hot cache. That's fine because
693 we care most about hot paths that are probably in cache already.
694
695 An example of the output:
696
697 START
698 first=3672 [COLD CACHED]
699 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
700 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
701 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
702 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
703 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
704 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
705
706
707config RING_BUFFER_BENCHMARK
708 tristate "Ring buffer benchmark stress tester"
709 depends on RING_BUFFER
710 help
711 This option creates a test to stress the ring buffer and benchmark it.
712 It creates its own ring buffer such that it will not interfere with
713 any other users of the ring buffer (such as ftrace). It then creates
714 a producer and consumer that will run for 10 seconds and sleep for
715 10 seconds. Each interval it will print out the number of events
716 it recorded and give a rough estimate of how long each iteration took.
717
718 It does not disable interrupts or raise its priority, so it may be
719 affected by processes that are running.
720
721 If unsure, say N.
722
723config RING_BUFFER_STARTUP_TEST
724 bool "Ring buffer startup self test"
725 depends on RING_BUFFER
726 help
727 Run a simple self test on the ring buffer on boot up. Late in the
728 kernel boot sequence, the test will start that kicks off
729 a thread per cpu. Each thread will write various size events
730 into the ring buffer. Another thread is created to send IPIs
731 to each of the threads, where the IPI handler will also write
732 to the ring buffer, to test/stress the nesting ability.
733 If any anomalies are discovered, a warning will be displayed
734 and all ring buffers will be disabled.
735
736 The test runs for 10 seconds. This will slow your boot time
737 by at least 10 more seconds.
738
739 At the end of the test, statics and more checks are done.
740 It will output the stats of each per cpu buffer. What
741 was written, the sizes, what was read, what was lost, and
742 other similar details.
743
744 If unsure, say N
745
746config PREEMPTIRQ_DELAY_TEST
747 tristate "Preempt / IRQ disable delay thread to test latency tracers"
748 depends on m
749 help
750 Select this option to build a test module that can help test latency
751 tracers by executing a preempt or irq disable section with a user
752 configurable delay. The module busy waits for the duration of the
753 critical section.
754
755 For example, the following invocation forces a one-time irq-disabled
756 critical section for 500us:
757 modprobe preemptirq_delay_test test_mode=irq delay=500000
758
759 If unsure, say N
760
761config TRACE_EVAL_MAP_FILE
762 bool "Show eval mappings for trace events"
763 depends on TRACING
764 help
765 The "print fmt" of the trace events will show the enum/sizeof names
766 instead of their values. This can cause problems for user space tools
767 that use this string to parse the raw data as user space does not know
768 how to convert the string to its value.
769
770 To fix this, there's a special macro in the kernel that can be used
771 to convert an enum/sizeof into its value. If this macro is used, then
772 the print fmt strings will be converted to their values.
773
774 If something does not get converted properly, this option can be
775 used to show what enums/sizeof the kernel tried to convert.
776
777 This option is for debugging the conversions. A file is created
778 in the tracing directory called "eval_map" that will show the
779 names matched with their values and what trace event system they
780 belong too.
781
782 Normally, the mapping of the strings to values will be freed after
783 boot up or module load. With this option, they will not be freed, as
784 they are needed for the "eval_map" file. Enabling this option will
785 increase the memory footprint of the running kernel.
786
787 If unsure, say N
788
789config GCOV_PROFILE_FTRACE
790 bool "Enable GCOV profiling on ftrace subsystem"
791 depends on GCOV_KERNEL
792 help
793 Enable GCOV profiling on ftrace subsystem for checking
794 which functions/lines are tested.
795
796 If unsure, say N.
797
798 Note that on a kernel compiled with this config, ftrace will
799 run significantly slower.
800
801endif # FTRACE
802
803endif # TRACING_SUPPORT
804