2 # Architectures that offer an FUNCTION_TRACER implementation should
3 # select HAVE_FUNCTION_TRACER:
6 config USER_STACKTRACE_SUPPORT
12 config HAVE_FTRACE_NMI_ENTER
15 See Documentation/trace/ftrace-design.rst
17 config HAVE_FUNCTION_TRACER
20 See Documentation/trace/ftrace-design.rst
22 config HAVE_FUNCTION_GRAPH_TRACER
25 See Documentation/trace/ftrace-design.rst
27 config HAVE_DYNAMIC_FTRACE
30 See Documentation/trace/ftrace-design.rst
32 config HAVE_DYNAMIC_FTRACE_WITH_REGS
35 config HAVE_FTRACE_MCOUNT_RECORD
38 See Documentation/trace/ftrace-design.rst
40 config HAVE_SYSCALL_TRACEPOINTS
43 See Documentation/trace/ftrace-design.rst
48 Arch supports the gcc options -pg with -mfentry
50 config HAVE_NOP_MCOUNT
53 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
55 config HAVE_C_RECORDMCOUNT
58 C version of recordmcount available?
60 config TRACER_MAX_TRACE
71 config FTRACE_NMI_ENTER
73 depends on HAVE_FTRACE_NMI_ENTER
77 select CONTEXT_SWITCH_TRACER
81 config CONTEXT_SWITCH_TRACER
84 config RING_BUFFER_ALLOW_SWAP
87 Allow the use of ring_buffer_swap_cpu.
88 Adds a very slight overhead to tracing when enabled.
90 config PREEMPTIRQ_TRACEPOINTS
92 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
96 Create preempt/irq toggle tracepoints if needed, so that other parts
97 of the kernel can use them to generate or add hooks to them.
99 # All tracer options should select GENERIC_TRACER. For those options that are
100 # enabled by all tracers (context switch and event tracer) they select TRACING.
101 # This allows those options to appear when no other tracer is selected. But the
102 # options do not appear when something else selects it. We need the two options
103 # GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
104 # hiding of the automatic options.
110 select STACKTRACE if STACKTRACE_SUPPORT
117 config GENERIC_TRACER
122 # Minimum requirements an architecture has to meet for us to
123 # be able to offer generic tracing facilities:
125 config TRACING_SUPPORT
127 depends on TRACE_IRQFLAGS_SUPPORT
128 depends on STACKTRACE_SUPPORT
135 default y if DEBUG_KERNEL
137 Enable the kernel tracing infrastructure.
141 config FUNCTION_TRACER
142 bool "Kernel Function Tracer"
143 depends on HAVE_FUNCTION_TRACER
145 select GENERIC_TRACER
146 select CONTEXT_SWITCH_TRACER
148 select TASKS_RCU if PREEMPT
150 Enable the kernel to trace every kernel function. This is done
151 by using a compiler feature to insert a small, 5-byte No-Operation
152 instruction at the beginning of every kernel function, which NOP
153 sequence is then dynamically patched into a tracer call when
154 tracing is enabled by the administrator. If it's runtime disabled
155 (the bootup default), then the overhead of the instructions is very
156 small and not measurable even in micro-benchmarks.
158 config FUNCTION_GRAPH_TRACER
159 bool "Kernel Function Graph Tracer"
160 depends on HAVE_FUNCTION_GRAPH_TRACER
161 depends on FUNCTION_TRACER
162 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
165 Enable the kernel to trace a function at both its return
167 Its first purpose is to trace the duration of functions and
168 draw a call graph for each thread with some information like
169 the return value. This is done by setting the current return
170 address on the current task structure into a stack of calls.
172 config TRACE_PREEMPT_TOGGLE
175 Enables hooks which will be called when preemption is first disabled,
178 config PREEMPTIRQ_EVENTS
179 bool "Enable trace events for preempt and irq disable/enable"
180 select TRACE_IRQFLAGS
181 select TRACE_PREEMPT_TOGGLE if PREEMPT
182 select GENERIC_TRACER
185 Enable tracing of disable and enable events for preemption and irqs.
187 config IRQSOFF_TRACER
188 bool "Interrupts-off Latency Tracer"
190 depends on TRACE_IRQFLAGS_SUPPORT
191 depends on !ARCH_USES_GETTIMEOFFSET
192 select TRACE_IRQFLAGS
193 select GENERIC_TRACER
194 select TRACER_MAX_TRACE
195 select RING_BUFFER_ALLOW_SWAP
196 select TRACER_SNAPSHOT
197 select TRACER_SNAPSHOT_PER_CPU_SWAP
199 This option measures the time spent in irqs-off critical
200 sections, with microsecond accuracy.
202 The default measurement method is a maximum search, which is
203 disabled by default and can be runtime (re-)started
206 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
208 (Note that kernel size and overhead increase with this option
209 enabled. This option and the preempt-off timing option can be
210 used together or separately.)
212 config PREEMPT_TRACER
213 bool "Preemption-off Latency Tracer"
215 depends on !ARCH_USES_GETTIMEOFFSET
217 select GENERIC_TRACER
218 select TRACER_MAX_TRACE
219 select RING_BUFFER_ALLOW_SWAP
220 select TRACER_SNAPSHOT
221 select TRACER_SNAPSHOT_PER_CPU_SWAP
222 select TRACE_PREEMPT_TOGGLE
224 This option measures the time spent in preemption-off critical
225 sections, with microsecond accuracy.
227 The default measurement method is a maximum search, which is
228 disabled by default and can be runtime (re-)started
231 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
233 (Note that kernel size and overhead increase with this option
234 enabled. This option and the irqs-off timing option can be
235 used together or separately.)
238 bool "Scheduling Latency Tracer"
239 select GENERIC_TRACER
240 select CONTEXT_SWITCH_TRACER
241 select TRACER_MAX_TRACE
242 select TRACER_SNAPSHOT
244 This tracer tracks the latency of the highest priority task
245 to be scheduled in, starting from the point it has woken up.
248 bool "Tracer to detect hardware latencies (like SMIs)"
249 select GENERIC_TRACER
251 This tracer, when enabled will create one or more kernel threads,
252 depending on what the cpumask file is set to, which each thread
253 spinning in a loop looking for interruptions caused by
254 something other than the kernel. For example, if a
255 System Management Interrupt (SMI) takes a noticeable amount of
256 time, this tracer will detect it. This is useful for testing
257 if a system is reliable for Real Time tasks.
259 Some files are created in the tracing directory when this
262 hwlat_detector/width - time in usecs for how long to spin for
263 hwlat_detector/window - time in usecs between the start of each
266 A kernel thread is created that will spin with interrupts disabled
267 for "width" microseconds in every "window" cycle. It will not spin
268 for "window - width" microseconds, where the system can
271 The output will appear in the trace and trace_pipe files.
273 When the tracer is not running, it has no affect on the system,
274 but when it is running, it can cause the system to be
275 periodically non responsive. Do not run this tracer on a
278 To enable this tracer, echo in "hwlat" into the current_tracer
279 file. Every time a latency is greater than tracing_thresh, it will
280 be recorded into the ring buffer.
282 config ENABLE_DEFAULT_TRACERS
283 bool "Trace process context switches and events"
284 depends on !GENERIC_TRACER
287 This tracer hooks to various trace points in the kernel,
288 allowing the user to pick and choose which trace point they
289 want to trace. It also includes the sched_switch tracer plugin.
291 config FTRACE_SYSCALLS
292 bool "Trace syscalls"
293 depends on HAVE_SYSCALL_TRACEPOINTS
294 select GENERIC_TRACER
297 Basic tracer to catch the syscall entry and exit events.
299 config TRACER_SNAPSHOT
300 bool "Create a snapshot trace buffer"
301 select TRACER_MAX_TRACE
303 Allow tracing users to take snapshot of the current buffer using the
304 ftrace interface, e.g.:
306 echo 1 > /sys/kernel/debug/tracing/snapshot
309 config TRACER_SNAPSHOT_PER_CPU_SWAP
310 bool "Allow snapshot to swap per CPU"
311 depends on TRACER_SNAPSHOT
312 select RING_BUFFER_ALLOW_SWAP
314 Allow doing a snapshot of a single CPU buffer instead of a
315 full swap (all buffers). If this is set, then the following is
318 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
320 After which, only the tracing buffer for CPU 2 was swapped with
321 the main tracing buffer, and the other CPU buffers remain the same.
323 When this is enabled, this adds a little more overhead to the
324 trace recording, as it needs to add some checks to synchronize
325 recording with swaps. But this does not affect the performance
326 of the overall system. This is enabled by default when the preempt
327 or irq latency tracers are enabled, as those need to swap as well
328 and already adds the overhead (plus a lot more).
330 config TRACE_BRANCH_PROFILING
332 select GENERIC_TRACER
335 prompt "Branch Profiling"
336 default BRANCH_PROFILE_NONE
338 The branch profiling is a software profiler. It will add hooks
339 into the C conditionals to test which path a branch takes.
341 The likely/unlikely profiler only looks at the conditions that
342 are annotated with a likely or unlikely macro.
344 The "all branch" profiler will profile every if-statement in the
345 kernel. This profiler will also enable the likely/unlikely
348 Either of the above profilers adds a bit of overhead to the system.
349 If unsure, choose "No branch profiling".
351 config BRANCH_PROFILE_NONE
352 bool "No branch profiling"
354 No branch profiling. Branch profiling adds a bit of overhead.
355 Only enable it if you want to analyse the branching behavior.
356 Otherwise keep it disabled.
358 config PROFILE_ANNOTATED_BRANCHES
359 bool "Trace likely/unlikely profiler"
360 select TRACE_BRANCH_PROFILING
362 This tracer profiles all likely and unlikely macros
363 in the kernel. It will display the results in:
365 /sys/kernel/debug/tracing/trace_stat/branch_annotated
367 Note: this will add a significant overhead; only turn this
368 on if you need to profile the system's use of these macros.
370 config PROFILE_ALL_BRANCHES
371 bool "Profile all if conditionals" if !FORTIFY_SOURCE
372 select TRACE_BRANCH_PROFILING
374 This tracer profiles all branch conditions. Every if ()
375 taken in the kernel is recorded whether it hit or miss.
376 The results will be displayed in:
378 /sys/kernel/debug/tracing/trace_stat/branch_all
380 This option also enables the likely/unlikely profiler.
382 This configuration, when enabled, will impose a great overhead
383 on the system. This should only be enabled when the system
384 is to be analyzed in much detail.
387 config TRACING_BRANCHES
390 Selected by tracers that will trace the likely and unlikely
391 conditions. This prevents the tracers themselves from being
392 profiled. Profiling the tracing infrastructure can only happen
393 when the likelys and unlikelys are not being traced.
396 bool "Trace likely/unlikely instances"
397 depends on TRACE_BRANCH_PROFILING
398 select TRACING_BRANCHES
400 This traces the events of likely and unlikely condition
401 calls in the kernel. The difference between this and the
402 "Trace likely/unlikely profiler" is that this is not a
403 histogram of the callers, but actually places the calling
404 events into a running trace buffer to see when and where the
405 events happened, as well as their results.
410 bool "Trace max stack"
411 depends on HAVE_FUNCTION_TRACER
412 select FUNCTION_TRACER
416 This special tracer records the maximum stack footprint of the
417 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
419 This tracer works by hooking into every function call that the
420 kernel executes, and keeping a maximum stack depth value and
421 stack-trace saved. If this is configured with DYNAMIC_FTRACE
422 then it will not have any overhead while the stack tracer
425 To enable the stack tracer on bootup, pass in 'stacktrace'
426 on the kernel command line.
428 The stack tracer can also be enabled or disabled via the
429 sysctl kernel.stack_tracer_enabled
433 config BLK_DEV_IO_TRACE
434 bool "Support for tracing block IO actions"
440 select GENERIC_TRACER
443 Say Y here if you want to be able to trace the block layer actions
444 on a given queue. Tracing allows you to see any traffic happening
445 on a block device queue. For more information (and the userspace
446 support tools needed), fetch the blktrace tools from:
448 git://git.kernel.dk/blktrace.git
450 Tracing also is possible using the ftrace interface, e.g.:
452 echo 1 > /sys/block/sda/sda1/trace/enable
453 echo blk > /sys/kernel/debug/tracing/current_tracer
454 cat /sys/kernel/debug/tracing/trace_pipe
460 depends on HAVE_REGS_AND_STACK_ACCESS_API
461 bool "Enable kprobes-based dynamic events"
464 select DYNAMIC_EVENTS
467 This allows the user to add tracing events (similar to tracepoints)
468 on the fly via the ftrace interface. See
469 Documentation/trace/kprobetrace.rst for more details.
471 Those events can be inserted wherever kprobes can probe, and record
472 various register and memory values.
474 This option is also required by perf-probe subcommand of perf tools.
475 If you want to use perf tools, this option is strongly recommended.
477 config KPROBE_EVENTS_ON_NOTRACE
478 bool "Do NOT protect notrace function from kprobe events"
479 depends on KPROBE_EVENTS
480 depends on KPROBES_ON_FTRACE
483 This is only for the developers who want to debug ftrace itself
486 If kprobes can use ftrace instead of breakpoint, ftrace related
487 functions are protected from kprobe-events to prevent an infinit
488 recursion or any unexpected execution path which leads to a kernel
491 This option disables such protection and allows you to put kprobe
492 events on ftrace functions for debugging ftrace by itself.
493 Note that this might let you shoot yourself in the foot.
498 bool "Enable uprobes-based dynamic events"
499 depends on ARCH_SUPPORTS_UPROBES
501 depends on PERF_EVENTS
504 select DYNAMIC_EVENTS
508 This allows the user to add tracing events on top of userspace
509 dynamic events (similar to tracepoints) on the fly via the trace
510 events interface. Those events can be inserted wherever uprobes
511 can probe, and record various registers.
512 This option is required if you plan to use perf-probe subcommand
513 of perf tools on user space applications.
516 depends on BPF_SYSCALL
517 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
521 This allows the user to attach BPF programs to kprobe events.
523 config DYNAMIC_EVENTS
529 config DYNAMIC_FTRACE
530 bool "enable/disable function tracing dynamically"
531 depends on FUNCTION_TRACER
532 depends on HAVE_DYNAMIC_FTRACE
535 This option will modify all the calls to function tracing
536 dynamically (will patch them out of the binary image and
537 replace them with a No-Op instruction) on boot up. During
538 compile time, a table is made of all the locations that ftrace
539 can function trace, and this table is linked into the kernel
540 image. When this is enabled, functions can be individually
541 enabled, and the functions not enabled will not affect
542 performance of the system.
544 See the files in /sys/kernel/debug/tracing:
545 available_filter_functions
549 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
550 otherwise has native performance as long as no tracing is active.
552 config DYNAMIC_FTRACE_WITH_REGS
554 depends on DYNAMIC_FTRACE
555 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
557 config FUNCTION_PROFILER
558 bool "Kernel function profiler"
559 depends on FUNCTION_TRACER
562 This option enables the kernel function profiler. A file is created
563 in debugfs called function_profile_enabled which defaults to zero.
564 When a 1 is echoed into this file profiling begins, and when a
565 zero is entered, profiling stops. A "functions" file is created in
566 the trace_stat directory; this file shows the list of functions that
567 have been hit and their counters.
571 config BPF_KPROBE_OVERRIDE
572 bool "Enable BPF programs to override a kprobed function"
573 depends on BPF_EVENTS
574 depends on FUNCTION_ERROR_INJECTION
577 Allows BPF to override the execution of a probed function and
578 set a different return value. This is used for error injection.
580 config FTRACE_MCOUNT_RECORD
582 depends on DYNAMIC_FTRACE
583 depends on HAVE_FTRACE_MCOUNT_RECORD
585 config FTRACE_SELFTEST
588 config FTRACE_STARTUP_TEST
589 bool "Perform a startup test on ftrace"
590 depends on GENERIC_TRACER
591 select FTRACE_SELFTEST
593 This option performs a series of startup tests on ftrace. On bootup
594 a series of tests are made to verify that the tracer is
595 functioning properly. It will do tests on all the configured
598 config EVENT_TRACE_TEST_SYSCALLS
599 bool "Run selftest on syscall events"
600 depends on FTRACE_STARTUP_TEST
602 This option will also enable testing every syscall event.
603 It only enables the event and disables it and runs various loads
604 with the event enabled. This adds a bit more time for kernel boot
605 up since it runs this on every system call defined.
607 TBD - enable a way to actually call the syscalls as we test their
611 bool "Memory mapped IO tracing"
612 depends on HAVE_MMIOTRACE_SUPPORT && PCI
613 select GENERIC_TRACER
615 Mmiotrace traces Memory Mapped I/O access and is meant for
616 debugging and reverse engineering. It is called from the ioremap
617 implementation and works via page faults. Tracing is disabled by
618 default and can be enabled at run-time.
620 See Documentation/trace/mmiotrace.rst.
621 If you are not helping to develop drivers, say N.
625 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
627 tracing_map is a special-purpose lock-free map for tracing,
628 separated out as a stand-alone facility in order to allow it
629 to be shared between multiple tracers. It isn't meant to be
630 generally used outside of that context, and is normally
631 selected by tracers that use it.
634 bool "Histogram triggers"
635 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
638 select DYNAMIC_EVENTS
641 Hist triggers allow one or more arbitrary trace event fields
642 to be aggregated into hash tables and dumped to stdout by
643 reading a debugfs/tracefs file. They're useful for
644 gathering quick and dirty (though precise) summaries of
645 event activity as an initial guide for further investigation
646 using more advanced tools.
648 Inter-event tracing of quantities such as latencies is also
649 supported using hist triggers under this option.
651 See Documentation/trace/histogram.rst.
654 config MMIOTRACE_TEST
655 tristate "Test module for mmiotrace"
656 depends on MMIOTRACE && m
658 This is a dumb module for testing mmiotrace. It is very dangerous
659 as it will write garbage to IO memory starting at a given address.
660 However, it should be safe to use on e.g. unused portion of VRAM.
662 Say N, unless you absolutely know what you are doing.
664 config TRACEPOINT_BENCHMARK
665 bool "Add tracepoint that benchmarks tracepoints"
667 This option creates the tracepoint "benchmark:benchmark_event".
668 When the tracepoint is enabled, it kicks off a kernel thread that
669 goes into an infinite loop (calling cond_sched() to let other tasks
670 run), and calls the tracepoint. Each iteration will record the time
671 it took to write to the tracepoint and the next iteration that
672 data will be passed to the tracepoint itself. That is, the tracepoint
673 will report the time it took to do the previous tracepoint.
674 The string written to the tracepoint is a static string of 128 bytes
675 to keep the time the same. The initial string is simply a write of
676 "START". The second string records the cold cache time of the first
677 write which is not added to the rest of the calculations.
679 As it is a tight loop, it benchmarks as hot cache. That's fine because
680 we care most about hot paths that are probably in cache already.
682 An example of the output:
685 first=3672 [COLD CACHED]
686 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
687 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
688 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
689 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
690 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
691 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
694 config RING_BUFFER_BENCHMARK
695 tristate "Ring buffer benchmark stress tester"
696 depends on RING_BUFFER
698 This option creates a test to stress the ring buffer and benchmark it.
699 It creates its own ring buffer such that it will not interfere with
700 any other users of the ring buffer (such as ftrace). It then creates
701 a producer and consumer that will run for 10 seconds and sleep for
702 10 seconds. Each interval it will print out the number of events
703 it recorded and give a rough estimate of how long each iteration took.
705 It does not disable interrupts or raise its priority, so it may be
706 affected by processes that are running.
710 config RING_BUFFER_STARTUP_TEST
711 bool "Ring buffer startup self test"
712 depends on RING_BUFFER
714 Run a simple self test on the ring buffer on boot up. Late in the
715 kernel boot sequence, the test will start that kicks off
716 a thread per cpu. Each thread will write various size events
717 into the ring buffer. Another thread is created to send IPIs
718 to each of the threads, where the IPI handler will also write
719 to the ring buffer, to test/stress the nesting ability.
720 If any anomalies are discovered, a warning will be displayed
721 and all ring buffers will be disabled.
723 The test runs for 10 seconds. This will slow your boot time
724 by at least 10 more seconds.
726 At the end of the test, statics and more checks are done.
727 It will output the stats of each per cpu buffer. What
728 was written, the sizes, what was read, what was lost, and
729 other similar details.
733 config PREEMPTIRQ_DELAY_TEST
734 tristate "Preempt / IRQ disable delay thread to test latency tracers"
737 Select this option to build a test module that can help test latency
738 tracers by executing a preempt or irq disable section with a user
739 configurable delay. The module busy waits for the duration of the
742 For example, the following invocation forces a one-time irq-disabled
743 critical section for 500us:
744 modprobe preemptirq_delay_test test_mode=irq delay=500000
748 config TRACE_EVAL_MAP_FILE
749 bool "Show eval mappings for trace events"
752 The "print fmt" of the trace events will show the enum/sizeof names
753 instead of their values. This can cause problems for user space tools
754 that use this string to parse the raw data as user space does not know
755 how to convert the string to its value.
757 To fix this, there's a special macro in the kernel that can be used
758 to convert an enum/sizeof into its value. If this macro is used, then
759 the print fmt strings will be converted to their values.
761 If something does not get converted properly, this option can be
762 used to show what enums/sizeof the kernel tried to convert.
764 This option is for debugging the conversions. A file is created
765 in the tracing directory called "eval_map" that will show the
766 names matched with their values and what trace event system they
769 Normally, the mapping of the strings to values will be freed after
770 boot up or module load. With this option, they will not be freed, as
771 they are needed for the "eval_map" file. Enabling this option will
772 increase the memory footprint of the running kernel.
776 config TRACING_EVENTS_GPIO
777 bool "Trace gpio events"
781 Enable tracing events for gpio subsystem
783 config GCOV_PROFILE_FTRACE
784 bool "Enable GCOV profiling on ftrace subsystem"
785 depends on GCOV_KERNEL
787 Enable GCOV profiling on ftrace subsystem for checking
788 which functions/lines are tested.
792 Note that on a kernel compiled with this config, ftrace will
793 run significantly slower.
797 endif # TRACING_SUPPORT