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_FTRACE_NMI_ENTER
16 See Documentation/trace/ftrace-design.rst
18 config HAVE_FUNCTION_TRACER
21 See Documentation/trace/ftrace-design.rst
23 config HAVE_FUNCTION_GRAPH_TRACER
26 See Documentation/trace/ftrace-design.rst
28 config HAVE_DYNAMIC_FTRACE
31 See Documentation/trace/ftrace-design.rst
33 config HAVE_DYNAMIC_FTRACE_WITH_REGS
36 config HAVE_FTRACE_MCOUNT_RECORD
39 See Documentation/trace/ftrace-design.rst
41 config HAVE_SYSCALL_TRACEPOINTS
44 See Documentation/trace/ftrace-design.rst
49 Arch supports the gcc options -pg with -mfentry
51 config HAVE_NOP_MCOUNT
54 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
56 config HAVE_C_RECORDMCOUNT
59 C version of recordmcount available?
61 config TRACER_MAX_TRACE
72 config FTRACE_NMI_ENTER
74 depends on HAVE_FTRACE_NMI_ENTER
78 select CONTEXT_SWITCH_TRACER
82 config CONTEXT_SWITCH_TRACER
85 config RING_BUFFER_ALLOW_SWAP
88 Allow the use of ring_buffer_swap_cpu.
89 Adds a very slight overhead to tracing when enabled.
91 config PREEMPTIRQ_TRACEPOINTS
93 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
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.
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.
111 select STACKTRACE if STACKTRACE_SUPPORT
118 config GENERIC_TRACER
123 # Minimum requirements an architecture has to meet for us to
124 # be able to offer generic tracing facilities:
126 config TRACING_SUPPORT
128 depends on TRACE_IRQFLAGS_SUPPORT
129 depends on STACKTRACE_SUPPORT
136 default y if DEBUG_KERNEL
138 Enable the kernel tracing infrastructure.
142 config FUNCTION_TRACER
143 bool "Kernel Function Tracer"
144 depends on HAVE_FUNCTION_TRACER
146 select GENERIC_TRACER
147 select CONTEXT_SWITCH_TRACER
149 select TASKS_RCU if PREEMPTION
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.
159 config 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
166 Enable the kernel to trace a function at both its return
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.
173 config TRACE_PREEMPT_TOGGLE
176 Enables hooks which will be called when preemption is first disabled,
179 config 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
186 Enable tracing of disable and enable events for preemption and irqs.
188 config IRQSOFF_TRACER
189 bool "Interrupts-off Latency Tracer"
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
200 This option measures the time spent in irqs-off critical
201 sections, with microsecond accuracy.
203 The default measurement method is a maximum search, which is
204 disabled by default and can be runtime (re-)started
207 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
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.)
213 config PREEMPT_TRACER
214 bool "Preemption-off Latency Tracer"
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
225 This option measures the time spent in preemption-off critical
226 sections, with microsecond accuracy.
228 The default measurement method is a maximum search, which is
229 disabled by default and can be runtime (re-)started
232 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
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.)
239 bool "Scheduling Latency Tracer"
240 select GENERIC_TRACER
241 select CONTEXT_SWITCH_TRACER
242 select TRACER_MAX_TRACE
243 select TRACER_SNAPSHOT
245 This tracer tracks the latency of the highest priority task
246 to be scheduled in, starting from the point it has woken up.
249 bool "Tracer to detect hardware latencies (like SMIs)"
250 select GENERIC_TRACER
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.
260 Some files are created in the tracing directory when this
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
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
272 The output will appear in the trace and trace_pipe files.
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
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.
283 config ENABLE_DEFAULT_TRACERS
284 bool "Trace process context switches and events"
285 depends on !GENERIC_TRACER
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.
292 config FTRACE_SYSCALLS
293 bool "Trace syscalls"
294 depends on HAVE_SYSCALL_TRACEPOINTS
295 select GENERIC_TRACER
298 Basic tracer to catch the syscall entry and exit events.
300 config TRACER_SNAPSHOT
301 bool "Create a snapshot trace buffer"
302 select TRACER_MAX_TRACE
304 Allow tracing users to take snapshot of the current buffer using the
305 ftrace interface, e.g.:
307 echo 1 > /sys/kernel/debug/tracing/snapshot
310 config TRACER_SNAPSHOT_PER_CPU_SWAP
311 bool "Allow snapshot to swap per CPU"
312 depends on TRACER_SNAPSHOT
313 select RING_BUFFER_ALLOW_SWAP
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
319 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
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.
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).
331 config TRACE_BRANCH_PROFILING
333 select GENERIC_TRACER
336 prompt "Branch Profiling"
337 default BRANCH_PROFILE_NONE
339 The branch profiling is a software profiler. It will add hooks
340 into the C conditionals to test which path a branch takes.
342 The likely/unlikely profiler only looks at the conditions that
343 are annotated with a likely or unlikely macro.
345 The "all branch" profiler will profile every if-statement in the
346 kernel. This profiler will also enable the likely/unlikely
349 Either of the above profilers adds a bit of overhead to the system.
350 If unsure, choose "No branch profiling".
352 config BRANCH_PROFILE_NONE
353 bool "No branch profiling"
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.
359 config PROFILE_ANNOTATED_BRANCHES
360 bool "Trace likely/unlikely profiler"
361 select TRACE_BRANCH_PROFILING
363 This tracer profiles all likely and unlikely macros
364 in the kernel. It will display the results in:
366 /sys/kernel/debug/tracing/trace_stat/branch_annotated
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.
371 config 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
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:
380 /sys/kernel/debug/tracing/trace_stat/branch_all
382 This option also enables the likely/unlikely profiler.
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.
389 config TRACING_BRANCHES
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.
398 bool "Trace likely/unlikely instances"
399 depends on TRACE_BRANCH_PROFILING
400 select TRACING_BRANCHES
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.
412 bool "Trace max stack"
413 depends on HAVE_FUNCTION_TRACER
414 select FUNCTION_TRACER
418 This special tracer records the maximum stack footprint of the
419 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
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
427 To enable the stack tracer on bootup, pass in 'stacktrace'
428 on the kernel command line.
430 The stack tracer can also be enabled or disabled via the
431 sysctl kernel.stack_tracer_enabled
435 config BLK_DEV_IO_TRACE
436 bool "Support for tracing block IO actions"
442 select GENERIC_TRACER
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:
450 git://git.kernel.dk/blktrace.git
452 Tracing also is possible using the ftrace interface, e.g.:
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
462 depends on HAVE_REGS_AND_STACK_ACCESS_API
463 bool "Enable kprobes-based dynamic events"
466 select DYNAMIC_EVENTS
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.
473 Those events can be inserted wherever kprobes can probe, and record
474 various register and memory values.
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.
479 config 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
485 This is only for the developers who want to debug ftrace itself
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
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.
500 bool "Enable uprobes-based dynamic events"
501 depends on ARCH_SUPPORTS_UPROBES
503 depends on PERF_EVENTS
506 select DYNAMIC_EVENTS
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.
518 depends on BPF_SYSCALL
519 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
523 This allows the user to attach BPF programs to kprobe events.
525 config DYNAMIC_EVENTS
531 config DYNAMIC_FTRACE
532 bool "enable/disable function tracing dynamically"
533 depends on FUNCTION_TRACER
534 depends on HAVE_DYNAMIC_FTRACE
537 This option will modify all the calls to function tracing
538 dynamically (will patch them out of the binary image and
539 replace them with a No-Op instruction) on boot up. During
540 compile time, a table is made of all the locations that ftrace
541 can function trace, and this table is linked into the kernel
542 image. When this is enabled, functions can be individually
543 enabled, and the functions not enabled will not affect
544 performance of the system.
546 See the files in /sys/kernel/debug/tracing:
547 available_filter_functions
551 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
552 otherwise has native performance as long as no tracing is active.
554 config DYNAMIC_FTRACE_WITH_REGS
556 depends on DYNAMIC_FTRACE
557 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
559 config FUNCTION_PROFILER
560 bool "Kernel function profiler"
561 depends on FUNCTION_TRACER
564 This option enables the kernel function profiler. A file is created
565 in debugfs called function_profile_enabled which defaults to zero.
566 When a 1 is echoed into this file profiling begins, and when a
567 zero is entered, profiling stops. A "functions" file is created in
568 the trace_stat directory; this file shows the list of functions that
569 have been hit and their counters.
573 config BPF_KPROBE_OVERRIDE
574 bool "Enable BPF programs to override a kprobed function"
575 depends on BPF_EVENTS
576 depends on FUNCTION_ERROR_INJECTION
579 Allows BPF to override the execution of a probed function and
580 set a different return value. This is used for error injection.
582 config FTRACE_MCOUNT_RECORD
584 depends on DYNAMIC_FTRACE
585 depends on HAVE_FTRACE_MCOUNT_RECORD
587 config FTRACE_SELFTEST
590 config FTRACE_STARTUP_TEST
591 bool "Perform a startup test on ftrace"
592 depends on GENERIC_TRACER
593 select FTRACE_SELFTEST
595 This option performs a series of startup tests on ftrace. On bootup
596 a series of tests are made to verify that the tracer is
597 functioning properly. It will do tests on all the configured
600 config EVENT_TRACE_STARTUP_TEST
601 bool "Run selftest on trace events"
602 depends on FTRACE_STARTUP_TEST
605 This option performs a test on all trace events in the system.
606 It basically just enables each event and runs some code that
607 will trigger events (not necessarily the event it enables)
608 This may take some time run as there are a lot of events.
610 config EVENT_TRACE_TEST_SYSCALLS
611 bool "Run selftest on syscall events"
612 depends on EVENT_TRACE_STARTUP_TEST
614 This option will also enable testing every syscall event.
615 It only enables the event and disables it and runs various loads
616 with the event enabled. This adds a bit more time for kernel boot
617 up since it runs this on every system call defined.
619 TBD - enable a way to actually call the syscalls as we test their
623 bool "Memory mapped IO tracing"
624 depends on HAVE_MMIOTRACE_SUPPORT && PCI
625 select GENERIC_TRACER
627 Mmiotrace traces Memory Mapped I/O access and is meant for
628 debugging and reverse engineering. It is called from the ioremap
629 implementation and works via page faults. Tracing is disabled by
630 default and can be enabled at run-time.
632 See Documentation/trace/mmiotrace.rst.
633 If you are not helping to develop drivers, say N.
637 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
639 tracing_map is a special-purpose lock-free map for tracing,
640 separated out as a stand-alone facility in order to allow it
641 to be shared between multiple tracers. It isn't meant to be
642 generally used outside of that context, and is normally
643 selected by tracers that use it.
646 bool "Histogram triggers"
647 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
650 select DYNAMIC_EVENTS
653 Hist triggers allow one or more arbitrary trace event fields
654 to be aggregated into hash tables and dumped to stdout by
655 reading a debugfs/tracefs file. They're useful for
656 gathering quick and dirty (though precise) summaries of
657 event activity as an initial guide for further investigation
658 using more advanced tools.
660 Inter-event tracing of quantities such as latencies is also
661 supported using hist triggers under this option.
663 See Documentation/trace/histogram.rst.
666 config MMIOTRACE_TEST
667 tristate "Test module for mmiotrace"
668 depends on MMIOTRACE && m
670 This is a dumb module for testing mmiotrace. It is very dangerous
671 as it will write garbage to IO memory starting at a given address.
672 However, it should be safe to use on e.g. unused portion of VRAM.
674 Say N, unless you absolutely know what you are doing.
676 config TRACEPOINT_BENCHMARK
677 bool "Add tracepoint that benchmarks tracepoints"
679 This option creates the tracepoint "benchmark:benchmark_event".
680 When the tracepoint is enabled, it kicks off a kernel thread that
681 goes into an infinite loop (calling cond_sched() to let other tasks
682 run), and calls the tracepoint. Each iteration will record the time
683 it took to write to the tracepoint and the next iteration that
684 data will be passed to the tracepoint itself. That is, the tracepoint
685 will report the time it took to do the previous tracepoint.
686 The string written to the tracepoint is a static string of 128 bytes
687 to keep the time the same. The initial string is simply a write of
688 "START". The second string records the cold cache time of the first
689 write which is not added to the rest of the calculations.
691 As it is a tight loop, it benchmarks as hot cache. That's fine because
692 we care most about hot paths that are probably in cache already.
694 An example of the output:
697 first=3672 [COLD CACHED]
698 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
699 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
700 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
701 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
702 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
703 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
706 config RING_BUFFER_BENCHMARK
707 tristate "Ring buffer benchmark stress tester"
708 depends on RING_BUFFER
710 This option creates a test to stress the ring buffer and benchmark it.
711 It creates its own ring buffer such that it will not interfere with
712 any other users of the ring buffer (such as ftrace). It then creates
713 a producer and consumer that will run for 10 seconds and sleep for
714 10 seconds. Each interval it will print out the number of events
715 it recorded and give a rough estimate of how long each iteration took.
717 It does not disable interrupts or raise its priority, so it may be
718 affected by processes that are running.
722 config RING_BUFFER_STARTUP_TEST
723 bool "Ring buffer startup self test"
724 depends on RING_BUFFER
726 Run a simple self test on the ring buffer on boot up. Late in the
727 kernel boot sequence, the test will start that kicks off
728 a thread per cpu. Each thread will write various size events
729 into the ring buffer. Another thread is created to send IPIs
730 to each of the threads, where the IPI handler will also write
731 to the ring buffer, to test/stress the nesting ability.
732 If any anomalies are discovered, a warning will be displayed
733 and all ring buffers will be disabled.
735 The test runs for 10 seconds. This will slow your boot time
736 by at least 10 more seconds.
738 At the end of the test, statics and more checks are done.
739 It will output the stats of each per cpu buffer. What
740 was written, the sizes, what was read, what was lost, and
741 other similar details.
745 config PREEMPTIRQ_DELAY_TEST
746 tristate "Preempt / IRQ disable delay thread to test latency tracers"
749 Select this option to build a test module that can help test latency
750 tracers by executing a preempt or irq disable section with a user
751 configurable delay. The module busy waits for the duration of the
754 For example, the following invocation forces a one-time irq-disabled
755 critical section for 500us:
756 modprobe preemptirq_delay_test test_mode=irq delay=500000
760 config TRACE_EVAL_MAP_FILE
761 bool "Show eval mappings for trace events"
764 The "print fmt" of the trace events will show the enum/sizeof names
765 instead of their values. This can cause problems for user space tools
766 that use this string to parse the raw data as user space does not know
767 how to convert the string to its value.
769 To fix this, there's a special macro in the kernel that can be used
770 to convert an enum/sizeof into its value. If this macro is used, then
771 the print fmt strings will be converted to their values.
773 If something does not get converted properly, this option can be
774 used to show what enums/sizeof the kernel tried to convert.
776 This option is for debugging the conversions. A file is created
777 in the tracing directory called "eval_map" that will show the
778 names matched with their values and what trace event system they
781 Normally, the mapping of the strings to values will be freed after
782 boot up or module load. With this option, they will not be freed, as
783 they are needed for the "eval_map" file. Enabling this option will
784 increase the memory footprint of the running kernel.
788 config GCOV_PROFILE_FTRACE
789 bool "Enable GCOV profiling on ftrace subsystem"
790 depends on GCOV_KERNEL
792 Enable GCOV profiling on ftrace subsystem for checking
793 which functions/lines are tested.
797 Note that on a kernel compiled with this config, ftrace will
798 run significantly slower.
802 endif # TRACING_SUPPORT