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