1 # SPDX-License-Identifier: GPL-2.0-only
3 # Architectures that offer an FUNCTION_TRACER implementation should
4 # select HAVE_FUNCTION_TRACER:
7 config USER_STACKTRACE_SUPPORT
13 config HAVE_FUNCTION_TRACER
16 See Documentation/trace/ftrace-design.rst
18 config HAVE_FUNCTION_GRAPH_TRACER
21 See Documentation/trace/ftrace-design.rst
23 config HAVE_DYNAMIC_FTRACE
26 See Documentation/trace/ftrace-design.rst
28 config HAVE_DYNAMIC_FTRACE_WITH_REGS
31 config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
34 config HAVE_FTRACE_MCOUNT_RECORD
37 See Documentation/trace/ftrace-design.rst
39 config HAVE_SYSCALL_TRACEPOINTS
42 See Documentation/trace/ftrace-design.rst
47 Arch supports the gcc options -pg with -mfentry
49 config HAVE_NOP_MCOUNT
52 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
54 config HAVE_C_RECORDMCOUNT
57 C version of recordmcount available?
59 config TRACER_MAX_TRACE
71 select CONTEXT_SWITCH_TRACER
75 config CONTEXT_SWITCH_TRACER
78 config RING_BUFFER_ALLOW_SWAP
81 Allow the use of ring_buffer_swap_cpu.
82 Adds a very slight overhead to tracing when enabled.
84 config PREEMPTIRQ_TRACEPOINTS
86 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
90 Create preempt/irq toggle tracepoints if needed, so that other parts
91 of the kernel can use them to generate or add hooks to them.
93 # All tracer options should select GENERIC_TRACER. For those options that are
94 # enabled by all tracers (context switch and event tracer) they select TRACING.
95 # This allows those options to appear when no other tracer is selected. But the
96 # options do not appear when something else selects it. We need the two options
97 # GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
98 # hiding of the automatic options.
103 select STACKTRACE if STACKTRACE_SUPPORT
110 config GENERIC_TRACER
115 # Minimum requirements an architecture has to meet for us to
116 # be able to offer generic tracing facilities:
118 config TRACING_SUPPORT
120 depends on TRACE_IRQFLAGS_SUPPORT
121 depends on STACKTRACE_SUPPORT
128 default y if DEBUG_KERNEL
130 Enable the kernel tracing infrastructure.
134 config BOOTTIME_TRACING
135 bool "Boot-time Tracing support"
139 Enable developer to setup ftrace subsystem via supplemental
140 kernel cmdline at boot time for debugging (tracing) driver
141 initialization and boot process.
143 config FUNCTION_TRACER
144 bool "Kernel Function Tracer"
145 depends on HAVE_FUNCTION_TRACER
147 select GENERIC_TRACER
148 select CONTEXT_SWITCH_TRACER
150 select TASKS_RCU if PREEMPTION
151 select TASKS_RUDE_RCU
153 Enable the kernel to trace every kernel function. This is done
154 by using a compiler feature to insert a small, 5-byte No-Operation
155 instruction at the beginning of every kernel function, which NOP
156 sequence is then dynamically patched into a tracer call when
157 tracing is enabled by the administrator. If it's runtime disabled
158 (the bootup default), then the overhead of the instructions is very
159 small and not measurable even in micro-benchmarks.
161 config FUNCTION_GRAPH_TRACER
162 bool "Kernel Function Graph Tracer"
163 depends on HAVE_FUNCTION_GRAPH_TRACER
164 depends on FUNCTION_TRACER
165 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
168 Enable the kernel to trace a function at both its return
170 Its first purpose is to trace the duration of functions and
171 draw a call graph for each thread with some information like
172 the return value. This is done by setting the current return
173 address on the current task structure into a stack of calls.
175 config DYNAMIC_FTRACE
176 bool "enable/disable function tracing dynamically"
177 depends on FUNCTION_TRACER
178 depends on HAVE_DYNAMIC_FTRACE
181 This option will modify all the calls to function tracing
182 dynamically (will patch them out of the binary image and
183 replace them with a No-Op instruction) on boot up. During
184 compile time, a table is made of all the locations that ftrace
185 can function trace, and this table is linked into the kernel
186 image. When this is enabled, functions can be individually
187 enabled, and the functions not enabled will not affect
188 performance of the system.
190 See the files in /sys/kernel/debug/tracing:
191 available_filter_functions
195 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
196 otherwise has native performance as long as no tracing is active.
198 config DYNAMIC_FTRACE_WITH_REGS
200 depends on DYNAMIC_FTRACE
201 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
203 config DYNAMIC_FTRACE_WITH_DIRECT_CALLS
205 depends on DYNAMIC_FTRACE_WITH_REGS
206 depends on HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
208 config FUNCTION_PROFILER
209 bool "Kernel function profiler"
210 depends on FUNCTION_TRACER
213 This option enables the kernel function profiler. A file is created
214 in debugfs called function_profile_enabled which defaults to zero.
215 When a 1 is echoed into this file profiling begins, and when a
216 zero is entered, profiling stops. A "functions" file is created in
217 the trace_stat directory; this file shows the list of functions that
218 have been hit and their counters.
223 bool "Trace max stack"
224 depends on HAVE_FUNCTION_TRACER
225 select FUNCTION_TRACER
229 This special tracer records the maximum stack footprint of the
230 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
232 This tracer works by hooking into every function call that the
233 kernel executes, and keeping a maximum stack depth value and
234 stack-trace saved. If this is configured with DYNAMIC_FTRACE
235 then it will not have any overhead while the stack tracer
238 To enable the stack tracer on bootup, pass in 'stacktrace'
239 on the kernel command line.
241 The stack tracer can also be enabled or disabled via the
242 sysctl kernel.stack_tracer_enabled
246 config TRACE_PREEMPT_TOGGLE
249 Enables hooks which will be called when preemption is first disabled,
252 config IRQSOFF_TRACER
253 bool "Interrupts-off Latency Tracer"
255 depends on TRACE_IRQFLAGS_SUPPORT
256 depends on !ARCH_USES_GETTIMEOFFSET
257 select TRACE_IRQFLAGS
258 select GENERIC_TRACER
259 select TRACER_MAX_TRACE
260 select RING_BUFFER_ALLOW_SWAP
261 select TRACER_SNAPSHOT
262 select TRACER_SNAPSHOT_PER_CPU_SWAP
264 This option measures the time spent in irqs-off critical
265 sections, with microsecond accuracy.
267 The default measurement method is a maximum search, which is
268 disabled by default and can be runtime (re-)started
271 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
273 (Note that kernel size and overhead increase with this option
274 enabled. This option and the preempt-off timing option can be
275 used together or separately.)
277 config PREEMPT_TRACER
278 bool "Preemption-off Latency Tracer"
280 depends on !ARCH_USES_GETTIMEOFFSET
281 depends on PREEMPTION
282 select GENERIC_TRACER
283 select TRACER_MAX_TRACE
284 select RING_BUFFER_ALLOW_SWAP
285 select TRACER_SNAPSHOT
286 select TRACER_SNAPSHOT_PER_CPU_SWAP
287 select TRACE_PREEMPT_TOGGLE
289 This option measures the time spent in preemption-off critical
290 sections, with microsecond accuracy.
292 The default measurement method is a maximum search, which is
293 disabled by default and can be runtime (re-)started
296 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
298 (Note that kernel size and overhead increase with this option
299 enabled. This option and the irqs-off timing option can be
300 used together or separately.)
303 bool "Scheduling Latency Tracer"
304 select GENERIC_TRACER
305 select CONTEXT_SWITCH_TRACER
306 select TRACER_MAX_TRACE
307 select TRACER_SNAPSHOT
309 This tracer tracks the latency of the highest priority task
310 to be scheduled in, starting from the point it has woken up.
313 bool "Tracer to detect hardware latencies (like SMIs)"
314 select GENERIC_TRACER
316 This tracer, when enabled will create one or more kernel threads,
317 depending on what the cpumask file is set to, which each thread
318 spinning in a loop looking for interruptions caused by
319 something other than the kernel. For example, if a
320 System Management Interrupt (SMI) takes a noticeable amount of
321 time, this tracer will detect it. This is useful for testing
322 if a system is reliable for Real Time tasks.
324 Some files are created in the tracing directory when this
327 hwlat_detector/width - time in usecs for how long to spin for
328 hwlat_detector/window - time in usecs between the start of each
331 A kernel thread is created that will spin with interrupts disabled
332 for "width" microseconds in every "window" cycle. It will not spin
333 for "window - width" microseconds, where the system can
336 The output will appear in the trace and trace_pipe files.
338 When the tracer is not running, it has no affect on the system,
339 but when it is running, it can cause the system to be
340 periodically non responsive. Do not run this tracer on a
343 To enable this tracer, echo in "hwlat" into the current_tracer
344 file. Every time a latency is greater than tracing_thresh, it will
345 be recorded into the ring buffer.
348 bool "Memory mapped IO tracing"
349 depends on HAVE_MMIOTRACE_SUPPORT && PCI
350 select GENERIC_TRACER
352 Mmiotrace traces Memory Mapped I/O access and is meant for
353 debugging and reverse engineering. It is called from the ioremap
354 implementation and works via page faults. Tracing is disabled by
355 default and can be enabled at run-time.
357 See Documentation/trace/mmiotrace.rst.
358 If you are not helping to develop drivers, say N.
360 config ENABLE_DEFAULT_TRACERS
361 bool "Trace process context switches and events"
362 depends on !GENERIC_TRACER
365 This tracer hooks to various trace points in the kernel,
366 allowing the user to pick and choose which trace point they
367 want to trace. It also includes the sched_switch tracer plugin.
369 config FTRACE_SYSCALLS
370 bool "Trace syscalls"
371 depends on HAVE_SYSCALL_TRACEPOINTS
372 select GENERIC_TRACER
375 Basic tracer to catch the syscall entry and exit events.
377 config TRACER_SNAPSHOT
378 bool "Create a snapshot trace buffer"
379 select TRACER_MAX_TRACE
381 Allow tracing users to take snapshot of the current buffer using the
382 ftrace interface, e.g.:
384 echo 1 > /sys/kernel/debug/tracing/snapshot
387 config TRACER_SNAPSHOT_PER_CPU_SWAP
388 bool "Allow snapshot to swap per CPU"
389 depends on TRACER_SNAPSHOT
390 select RING_BUFFER_ALLOW_SWAP
392 Allow doing a snapshot of a single CPU buffer instead of a
393 full swap (all buffers). If this is set, then the following is
396 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
398 After which, only the tracing buffer for CPU 2 was swapped with
399 the main tracing buffer, and the other CPU buffers remain the same.
401 When this is enabled, this adds a little more overhead to the
402 trace recording, as it needs to add some checks to synchronize
403 recording with swaps. But this does not affect the performance
404 of the overall system. This is enabled by default when the preempt
405 or irq latency tracers are enabled, as those need to swap as well
406 and already adds the overhead (plus a lot more).
408 config TRACE_BRANCH_PROFILING
410 select GENERIC_TRACER
413 prompt "Branch Profiling"
414 default BRANCH_PROFILE_NONE
416 The branch profiling is a software profiler. It will add hooks
417 into the C conditionals to test which path a branch takes.
419 The likely/unlikely profiler only looks at the conditions that
420 are annotated with a likely or unlikely macro.
422 The "all branch" profiler will profile every if-statement in the
423 kernel. This profiler will also enable the likely/unlikely
426 Either of the above profilers adds a bit of overhead to the system.
427 If unsure, choose "No branch profiling".
429 config BRANCH_PROFILE_NONE
430 bool "No branch profiling"
432 No branch profiling. Branch profiling adds a bit of overhead.
433 Only enable it if you want to analyse the branching behavior.
434 Otherwise keep it disabled.
436 config PROFILE_ANNOTATED_BRANCHES
437 bool "Trace likely/unlikely profiler"
438 select TRACE_BRANCH_PROFILING
440 This tracer profiles all likely and unlikely macros
441 in the kernel. It will display the results in:
443 /sys/kernel/debug/tracing/trace_stat/branch_annotated
445 Note: this will add a significant overhead; only turn this
446 on if you need to profile the system's use of these macros.
448 config PROFILE_ALL_BRANCHES
449 bool "Profile all if conditionals" if !FORTIFY_SOURCE
450 select TRACE_BRANCH_PROFILING
452 This tracer profiles all branch conditions. Every if ()
453 taken in the kernel is recorded whether it hit or miss.
454 The results will be displayed in:
456 /sys/kernel/debug/tracing/trace_stat/branch_all
458 This option also enables the likely/unlikely profiler.
460 This configuration, when enabled, will impose a great overhead
461 on the system. This should only be enabled when the system
462 is to be analyzed in much detail.
465 config TRACING_BRANCHES
468 Selected by tracers that will trace the likely and unlikely
469 conditions. This prevents the tracers themselves from being
470 profiled. Profiling the tracing infrastructure can only happen
471 when the likelys and unlikelys are not being traced.
474 bool "Trace likely/unlikely instances"
475 depends on TRACE_BRANCH_PROFILING
476 select TRACING_BRANCHES
478 This traces the events of likely and unlikely condition
479 calls in the kernel. The difference between this and the
480 "Trace likely/unlikely profiler" is that this is not a
481 histogram of the callers, but actually places the calling
482 events into a running trace buffer to see when and where the
483 events happened, as well as their results.
487 config BLK_DEV_IO_TRACE
488 bool "Support for tracing block IO actions"
494 select GENERIC_TRACER
497 Say Y here if you want to be able to trace the block layer actions
498 on a given queue. Tracing allows you to see any traffic happening
499 on a block device queue. For more information (and the userspace
500 support tools needed), fetch the blktrace tools from:
502 git://git.kernel.dk/blktrace.git
504 Tracing also is possible using the ftrace interface, e.g.:
506 echo 1 > /sys/block/sda/sda1/trace/enable
507 echo blk > /sys/kernel/debug/tracing/current_tracer
508 cat /sys/kernel/debug/tracing/trace_pipe
514 depends on HAVE_REGS_AND_STACK_ACCESS_API
515 bool "Enable kprobes-based dynamic events"
518 select DYNAMIC_EVENTS
521 This allows the user to add tracing events (similar to tracepoints)
522 on the fly via the ftrace interface. See
523 Documentation/trace/kprobetrace.rst for more details.
525 Those events can be inserted wherever kprobes can probe, and record
526 various register and memory values.
528 This option is also required by perf-probe subcommand of perf tools.
529 If you want to use perf tools, this option is strongly recommended.
531 config KPROBE_EVENTS_ON_NOTRACE
532 bool "Do NOT protect notrace function from kprobe events"
533 depends on KPROBE_EVENTS
534 depends on KPROBES_ON_FTRACE
537 This is only for the developers who want to debug ftrace itself
540 If kprobes can use ftrace instead of breakpoint, ftrace related
541 functions are protected from kprobe-events to prevent an infinit
542 recursion or any unexpected execution path which leads to a kernel
545 This option disables such protection and allows you to put kprobe
546 events on ftrace functions for debugging ftrace by itself.
547 Note that this might let you shoot yourself in the foot.
552 bool "Enable uprobes-based dynamic events"
553 depends on ARCH_SUPPORTS_UPROBES
555 depends on PERF_EVENTS
558 select DYNAMIC_EVENTS
562 This allows the user to add tracing events on top of userspace
563 dynamic events (similar to tracepoints) on the fly via the trace
564 events interface. Those events can be inserted wherever uprobes
565 can probe, and record various registers.
566 This option is required if you plan to use perf-probe subcommand
567 of perf tools on user space applications.
570 depends on BPF_SYSCALL
571 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
575 This allows the user to attach BPF programs to kprobe, uprobe, and
578 config DYNAMIC_EVENTS
584 config BPF_KPROBE_OVERRIDE
585 bool "Enable BPF programs to override a kprobed function"
586 depends on BPF_EVENTS
587 depends on FUNCTION_ERROR_INJECTION
590 Allows BPF to override the execution of a probed function and
591 set a different return value. This is used for error injection.
593 config FTRACE_MCOUNT_RECORD
595 depends on DYNAMIC_FTRACE
596 depends on HAVE_FTRACE_MCOUNT_RECORD
600 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
602 tracing_map is a special-purpose lock-free map for tracing,
603 separated out as a stand-alone facility in order to allow it
604 to be shared between multiple tracers. It isn't meant to be
605 generally used outside of that context, and is normally
606 selected by tracers that use it.
609 bool "Synthetic trace events"
611 select DYNAMIC_EVENTS
614 Synthetic events are user-defined trace events that can be
615 used to combine data from other trace events or in fact any
616 data source. Synthetic events can be generated indirectly
617 via the trace() action of histogram triggers or directly
618 by way of an in-kernel API.
620 See Documentation/trace/events.rst or
621 Documentation/trace/histogram.rst for details and examples.
626 bool "Histogram triggers"
627 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
630 select DYNAMIC_EVENTS
634 Hist triggers allow one or more arbitrary trace event fields
635 to be aggregated into hash tables and dumped to stdout by
636 reading a debugfs/tracefs file. They're useful for
637 gathering quick and dirty (though precise) summaries of
638 event activity as an initial guide for further investigation
639 using more advanced tools.
641 Inter-event tracing of quantities such as latencies is also
642 supported using hist triggers under this option.
644 See Documentation/trace/histogram.rst.
647 config TRACE_EVENT_INJECT
648 bool "Trace event injection"
651 Allow user-space to inject a specific trace event into the ring
652 buffer. This is mainly used for testing purpose.
656 config TRACEPOINT_BENCHMARK
657 bool "Add tracepoint that benchmarks tracepoints"
659 This option creates the tracepoint "benchmark:benchmark_event".
660 When the tracepoint is enabled, it kicks off a kernel thread that
661 goes into an infinite loop (calling cond_sched() to let other tasks
662 run), and calls the tracepoint. Each iteration will record the time
663 it took to write to the tracepoint and the next iteration that
664 data will be passed to the tracepoint itself. That is, the tracepoint
665 will report the time it took to do the previous tracepoint.
666 The string written to the tracepoint is a static string of 128 bytes
667 to keep the time the same. The initial string is simply a write of
668 "START". The second string records the cold cache time of the first
669 write which is not added to the rest of the calculations.
671 As it is a tight loop, it benchmarks as hot cache. That's fine because
672 we care most about hot paths that are probably in cache already.
674 An example of the output:
677 first=3672 [COLD CACHED]
678 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
679 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
680 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
681 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
682 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
683 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
686 config RING_BUFFER_BENCHMARK
687 tristate "Ring buffer benchmark stress tester"
688 depends on RING_BUFFER
690 This option creates a test to stress the ring buffer and benchmark it.
691 It creates its own ring buffer such that it will not interfere with
692 any other users of the ring buffer (such as ftrace). It then creates
693 a producer and consumer that will run for 10 seconds and sleep for
694 10 seconds. Each interval it will print out the number of events
695 it recorded and give a rough estimate of how long each iteration took.
697 It does not disable interrupts or raise its priority, so it may be
698 affected by processes that are running.
702 config TRACE_EVAL_MAP_FILE
703 bool "Show eval mappings for trace events"
706 The "print fmt" of the trace events will show the enum/sizeof names
707 instead of their values. This can cause problems for user space tools
708 that use this string to parse the raw data as user space does not know
709 how to convert the string to its value.
711 To fix this, there's a special macro in the kernel that can be used
712 to convert an enum/sizeof into its value. If this macro is used, then
713 the print fmt strings will be converted to their values.
715 If something does not get converted properly, this option can be
716 used to show what enums/sizeof the kernel tried to convert.
718 This option is for debugging the conversions. A file is created
719 in the tracing directory called "eval_map" that will show the
720 names matched with their values and what trace event system they
723 Normally, the mapping of the strings to values will be freed after
724 boot up or module load. With this option, they will not be freed, as
725 they are needed for the "eval_map" file. Enabling this option will
726 increase the memory footprint of the running kernel.
730 config GCOV_PROFILE_FTRACE
731 bool "Enable GCOV profiling on ftrace subsystem"
732 depends on GCOV_KERNEL
734 Enable GCOV profiling on ftrace subsystem for checking
735 which functions/lines are tested.
739 Note that on a kernel compiled with this config, ftrace will
740 run significantly slower.
742 config FTRACE_SELFTEST
745 config FTRACE_STARTUP_TEST
746 bool "Perform a startup test on ftrace"
747 depends on GENERIC_TRACER
748 select FTRACE_SELFTEST
750 This option performs a series of startup tests on ftrace. On bootup
751 a series of tests are made to verify that the tracer is
752 functioning properly. It will do tests on all the configured
755 config EVENT_TRACE_STARTUP_TEST
756 bool "Run selftest on trace events"
757 depends on FTRACE_STARTUP_TEST
760 This option performs a test on all trace events in the system.
761 It basically just enables each event and runs some code that
762 will trigger events (not necessarily the event it enables)
763 This may take some time run as there are a lot of events.
765 config EVENT_TRACE_TEST_SYSCALLS
766 bool "Run selftest on syscall events"
767 depends on EVENT_TRACE_STARTUP_TEST
769 This option will also enable testing every syscall event.
770 It only enables the event and disables it and runs various loads
771 with the event enabled. This adds a bit more time for kernel boot
772 up since it runs this on every system call defined.
774 TBD - enable a way to actually call the syscalls as we test their
777 config RING_BUFFER_STARTUP_TEST
778 bool "Ring buffer startup self test"
779 depends on RING_BUFFER
781 Run a simple self test on the ring buffer on boot up. Late in the
782 kernel boot sequence, the test will start that kicks off
783 a thread per cpu. Each thread will write various size events
784 into the ring buffer. Another thread is created to send IPIs
785 to each of the threads, where the IPI handler will also write
786 to the ring buffer, to test/stress the nesting ability.
787 If any anomalies are discovered, a warning will be displayed
788 and all ring buffers will be disabled.
790 The test runs for 10 seconds. This will slow your boot time
791 by at least 10 more seconds.
793 At the end of the test, statics and more checks are done.
794 It will output the stats of each per cpu buffer. What
795 was written, the sizes, what was read, what was lost, and
796 other similar details.
800 config MMIOTRACE_TEST
801 tristate "Test module for mmiotrace"
802 depends on MMIOTRACE && m
804 This is a dumb module for testing mmiotrace. It is very dangerous
805 as it will write garbage to IO memory starting at a given address.
806 However, it should be safe to use on e.g. unused portion of VRAM.
808 Say N, unless you absolutely know what you are doing.
810 config PREEMPTIRQ_DELAY_TEST
811 tristate "Test module to create a preempt / IRQ disable delay thread to test latency tracers"
814 Select this option to build a test module that can help test latency
815 tracers by executing a preempt or irq disable section with a user
816 configurable delay. The module busy waits for the duration of the
819 For example, the following invocation generates a burst of three
820 irq-disabled critical sections for 500us:
821 modprobe preemptirq_delay_test test_mode=irq delay=500 burst_size=3
825 config SYNTH_EVENT_GEN_TEST
826 tristate "Test module for in-kernel synthetic event generation"
827 depends on SYNTH_EVENTS
829 This option creates a test module to check the base
830 functionality of in-kernel synthetic event definition and
833 To test, insert the module, and then check the trace buffer
834 for the generated sample events.
838 config KPROBE_EVENT_GEN_TEST
839 tristate "Test module for in-kernel kprobe event generation"
840 depends on KPROBE_EVENTS
842 This option creates a test module to check the base
843 functionality of in-kernel kprobe event definition.
845 To test, insert the module, and then check the trace buffer
846 for the generated kprobe events.
850 config HIST_TRIGGERS_DEBUG
851 bool "Hist trigger debug support"
852 depends on HIST_TRIGGERS
854 Add "hist_debug" file for each event, which when read will
855 dump out a bunch of internal details about the hist triggers
856 defined on that event.
858 The hist_debug file serves a couple of purposes:
860 - Helps developers verify that nothing is broken.
862 - Provides educational information to support the details
863 of the hist trigger internals as described by
864 Documentation/trace/histogram-design.rst.
866 The hist_debug output only covers the data structures
867 related to the histogram definitions themselves and doesn't
868 display the internals of map buckets or variable values of
875 endif # TRACING_SUPPORT
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