kernel/trace/Kconfig

   1 # SPDX-License-Identifier: GPL-2.0-only
   2 #
   3 # Architectures that offer an FUNCTION_TRACER implementation should
   4 #  select HAVE_FUNCTION_TRACER:
   5 #
   6
   7 config USER_STACKTRACE_SUPPORT
   8         bool
   9
  10 config NOP_TRACER
  11         bool
  12
  13 config HAVE_FUNCTION_TRACER
  14         bool
  15         help
  16           See Documentation/trace/ftrace-design.rst
  17
  18 config HAVE_FUNCTION_GRAPH_TRACER
  19         bool
  20         help
  21           See Documentation/trace/ftrace-design.rst
  22
  23 config HAVE_DYNAMIC_FTRACE
  24         bool
  25         help
  26           See Documentation/trace/ftrace-design.rst
  27
  28 config HAVE_DYNAMIC_FTRACE_WITH_REGS
  29         bool
  30
  31 config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
  32         bool
  33
  34 config HAVE_FTRACE_MCOUNT_RECORD
  35         bool
  36         help
  37           See Documentation/trace/ftrace-design.rst
  38
  39 config HAVE_SYSCALL_TRACEPOINTS
  40         bool
  41         help
  42           See Documentation/trace/ftrace-design.rst
  43
  44 config HAVE_FENTRY
  45         bool
  46         help
  47           Arch supports the gcc options -pg with -mfentry
  48
  49 config HAVE_NOP_MCOUNT
  50         bool
  51         help
  52           Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
  53
  54 config HAVE_C_RECORDMCOUNT
  55         bool
  56         help
  57           C version of recordmcount available?
  58
  59 config TRACER_MAX_TRACE
  60         bool
  61
  62 config TRACE_CLOCK
  63         bool
  64
  65 config RING_BUFFER
  66         bool
  67         select TRACE_CLOCK
  68         select IRQ_WORK
  69
  70 config EVENT_TRACING
  71         select CONTEXT_SWITCH_TRACER
  72         select GLOB
  73         bool
  74
  75 config CONTEXT_SWITCH_TRACER
  76         bool
  77
  78 config RING_BUFFER_ALLOW_SWAP
  79         bool
  80         help
  81          Allow the use of ring_buffer_swap_cpu.
  82          Adds a very slight overhead to tracing when enabled.
  83
  84 config PREEMPTIRQ_TRACEPOINTS
  85         bool
  86         depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
  87         select TRACING
  88         default y
  89         help
  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.
  92
  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.
  99
 100 config TRACING
 101         bool
 102         select RING_BUFFER
 103         select STACKTRACE if STACKTRACE_SUPPORT
 104         select TRACEPOINTS
 105         select NOP_TRACER
 106         select BINARY_PRINTF
 107         select EVENT_TRACING
 108         select TRACE_CLOCK
 109
 110 config GENERIC_TRACER
 111         bool
 112         select TRACING
 113
 114 #
 115 # Minimum requirements an architecture has to meet for us to
 116 # be able to offer generic tracing facilities:
 117 #
 118 config TRACING_SUPPORT
 119         bool
 120         depends on TRACE_IRQFLAGS_SUPPORT
 121         depends on STACKTRACE_SUPPORT
 122         default y
 123
 124 if TRACING_SUPPORT
 125
 126 menuconfig FTRACE
 127         bool "Tracers"
 128         default y if DEBUG_KERNEL
 129         help
 130           Enable the kernel tracing infrastructure.
 131
 132 if FTRACE
 133
 134 config BOOTTIME_TRACING
 135         bool "Boot-time Tracing support"
 136         depends on TRACING
 137         select BOOT_CONFIG
 138         help
 139           Enable developer to setup ftrace subsystem via supplemental
 140           kernel cmdline at boot time for debugging (tracing) driver
 141           initialization and boot process.
 142
 143 config FUNCTION_TRACER
 144         bool "Kernel Function Tracer"
 145         depends on HAVE_FUNCTION_TRACER
 146         select KALLSYMS
 147         select GENERIC_TRACER
 148         select CONTEXT_SWITCH_TRACER
 149         select GLOB
 150         select TASKS_RCU if PREEMPTION
 151         select TASKS_RUDE_RCU
 152         help
 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.
 160
 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
 166         default y
 167         help
 168           Enable the kernel to trace a function at both its return
 169           and its entry.
 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.
 174
 175 config DYNAMIC_FTRACE
 176         bool "enable/disable function tracing dynamically"
 177         depends on FUNCTION_TRACER
 178         depends on HAVE_DYNAMIC_FTRACE
 179         default y
 180         help
 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.
 189
 190           See the files in /sys/kernel/debug/tracing:
 191             available_filter_functions
 192             set_ftrace_filter
 193             set_ftrace_notrace
 194
 195           This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
 196           otherwise has native performance as long as no tracing is active.
 197
 198 config DYNAMIC_FTRACE_WITH_REGS
 199         def_bool y
 200         depends on DYNAMIC_FTRACE
 201         depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
 202
 203 config DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 204         def_bool y
 205         depends on DYNAMIC_FTRACE
 206         depends on HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 207
 208 config FUNCTION_PROFILER
 209         bool "Kernel function profiler"
 210         depends on FUNCTION_TRACER
 211         default n
 212         help
 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.
 219
 220           If in doubt, say N.
 221
 222 config STACK_TRACER
 223         bool "Trace max stack"
 224         depends on HAVE_FUNCTION_TRACER
 225         select FUNCTION_TRACER
 226         select STACKTRACE
 227         select KALLSYMS
 228         help
 229           This special tracer records the maximum stack footprint of the
 230           kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
 231
 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
 236           is disabled.
 237
 238           To enable the stack tracer on bootup, pass in 'stacktrace'
 239           on the kernel command line.
 240
 241           The stack tracer can also be enabled or disabled via the
 242           sysctl kernel.stack_tracer_enabled
 243
 244           Say N if unsure.
 245
 246 config TRACE_PREEMPT_TOGGLE
 247         bool
 248         help
 249           Enables hooks which will be called when preemption is first disabled,
 250           and last enabled.
 251
 252 config IRQSOFF_TRACER
 253         bool "Interrupts-off Latency Tracer"
 254         default n
 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
 263         help
 264           This option measures the time spent in irqs-off critical
 265           sections, with microsecond accuracy.
 266
 267           The default measurement method is a maximum search, which is
 268           disabled by default and can be runtime (re-)started
 269           via:
 270
 271               echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 272
 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.)
 276
 277 config PREEMPT_TRACER
 278         bool "Preemption-off Latency Tracer"
 279         default n
 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
 288         help
 289           This option measures the time spent in preemption-off critical
 290           sections, with microsecond accuracy.
 291
 292           The default measurement method is a maximum search, which is
 293           disabled by default and can be runtime (re-)started
 294           via:
 295
 296               echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 297
 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.)
 301
 302 config SCHED_TRACER
 303         bool "Scheduling Latency Tracer"
 304         select GENERIC_TRACER
 305         select CONTEXT_SWITCH_TRACER
 306         select TRACER_MAX_TRACE
 307         select TRACER_SNAPSHOT
 308         help
 309           This tracer tracks the latency of the highest priority task
 310           to be scheduled in, starting from the point it has woken up.
 311
 312 config HWLAT_TRACER
 313         bool "Tracer to detect hardware latencies (like SMIs)"
 314         select GENERIC_TRACER
 315         help
 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.
 323
 324          Some files are created in the tracing directory when this
 325          is enabled:
 326
 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
 329                                      iteration
 330
 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
 334          continue to operate.
 335
 336          The output will appear in the trace and trace_pipe files.
 337
 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
 341          production system.
 342
 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.
 346
 347 config MMIOTRACE
 348         bool "Memory mapped IO tracing"
 349         depends on HAVE_MMIOTRACE_SUPPORT && PCI
 350         select GENERIC_TRACER
 351         help
 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.
 356
 357           See Documentation/trace/mmiotrace.rst.
 358           If you are not helping to develop drivers, say N.
 359
 360 config ENABLE_DEFAULT_TRACERS
 361         bool "Trace process context switches and events"
 362         depends on !GENERIC_TRACER
 363         select TRACING
 364         help
 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.
 368
 369 config FTRACE_SYSCALLS
 370         bool "Trace syscalls"
 371         depends on HAVE_SYSCALL_TRACEPOINTS
 372         select GENERIC_TRACER
 373         select KALLSYMS
 374         help
 375           Basic tracer to catch the syscall entry and exit events.
 376
 377 config TRACER_SNAPSHOT
 378         bool "Create a snapshot trace buffer"
 379         select TRACER_MAX_TRACE
 380         help
 381           Allow tracing users to take snapshot of the current buffer using the
 382           ftrace interface, e.g.:
 383
 384               echo 1 > /sys/kernel/debug/tracing/snapshot
 385               cat snapshot
 386
 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
 391         help
 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
 394           allowed:
 395
 396               echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
 397
 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.
 400
 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).
 407
 408 config TRACE_BRANCH_PROFILING
 409         bool
 410         select GENERIC_TRACER
 411
 412 choice
 413         prompt "Branch Profiling"
 414         default BRANCH_PROFILE_NONE
 415         help
 416          The branch profiling is a software profiler. It will add hooks
 417          into the C conditionals to test which path a branch takes.
 418
 419          The likely/unlikely profiler only looks at the conditions that
 420          are annotated with a likely or unlikely macro.
 421
 422          The "all branch" profiler will profile every if-statement in the
 423          kernel. This profiler will also enable the likely/unlikely
 424          profiler.
 425
 426          Either of the above profilers adds a bit of overhead to the system.
 427          If unsure, choose "No branch profiling".
 428
 429 config BRANCH_PROFILE_NONE
 430         bool "No branch profiling"
 431         help
 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.
 435
 436 config PROFILE_ANNOTATED_BRANCHES
 437         bool "Trace likely/unlikely profiler"
 438         select TRACE_BRANCH_PROFILING
 439         help
 440           This tracer profiles all likely and unlikely macros
 441           in the kernel. It will display the results in:
 442
 443           /sys/kernel/debug/tracing/trace_stat/branch_annotated
 444
 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.
 447
 448 config PROFILE_ALL_BRANCHES
 449         bool "Profile all if conditionals" if !FORTIFY_SOURCE
 450         select TRACE_BRANCH_PROFILING
 451         help
 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:
 455
 456           /sys/kernel/debug/tracing/trace_stat/branch_all
 457
 458           This option also enables the likely/unlikely profiler.
 459
 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.
 463 endchoice
 464
 465 config TRACING_BRANCHES
 466         bool
 467         help
 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.
 472
 473 config BRANCH_TRACER
 474         bool "Trace likely/unlikely instances"
 475         depends on TRACE_BRANCH_PROFILING
 476         select TRACING_BRANCHES
 477         help
 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.
 484
 485           Say N if unsure.
 486
 487 config BLK_DEV_IO_TRACE
 488         bool "Support for tracing block IO actions"
 489         depends on SYSFS
 490         depends on BLOCK
 491         select RELAY
 492         select DEBUG_FS
 493         select TRACEPOINTS
 494         select GENERIC_TRACER
 495         select STACKTRACE
 496         help
 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:
 501
 502           git://git.kernel.dk/blktrace.git
 503
 504           Tracing also is possible using the ftrace interface, e.g.:
 505
 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
 509
 510           If unsure, say N.
 511
 512 config KPROBE_EVENTS
 513         depends on KPROBES
 514         depends on HAVE_REGS_AND_STACK_ACCESS_API
 515         bool "Enable kprobes-based dynamic events"
 516         select TRACING
 517         select PROBE_EVENTS
 518         select DYNAMIC_EVENTS
 519         default y
 520         help
 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.
 524
 525           Those events can be inserted wherever kprobes can probe, and record
 526           various register and memory values.
 527
 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.
 530
 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
 535         default n
 536         help
 537           This is only for the developers who want to debug ftrace itself
 538           using kprobe events.
 539
 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
 543           crash.
 544
 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.
 548
 549           If unsure, say N.
 550
 551 config UPROBE_EVENTS
 552         bool "Enable uprobes-based dynamic events"
 553         depends on ARCH_SUPPORTS_UPROBES
 554         depends on MMU
 555         depends on PERF_EVENTS
 556         select UPROBES
 557         select PROBE_EVENTS
 558         select DYNAMIC_EVENTS
 559         select TRACING
 560         default y
 561         help
 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.
 568
 569 config BPF_EVENTS
 570         depends on BPF_SYSCALL
 571         depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
 572         bool
 573         default y
 574         help
 575           This allows the user to attach BPF programs to kprobe, uprobe, and
 576           tracepoint events.
 577
 578 config DYNAMIC_EVENTS
 579         def_bool n
 580
 581 config PROBE_EVENTS
 582         def_bool n
 583
 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
 588         default n
 589         help
 590          Allows BPF to override the execution of a probed function and
 591          set a different return value.  This is used for error injection.
 592
 593 config FTRACE_MCOUNT_RECORD
 594         def_bool y
 595         depends on DYNAMIC_FTRACE
 596         depends on HAVE_FTRACE_MCOUNT_RECORD
 597
 598 config TRACING_MAP
 599         bool
 600         depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
 601         help
 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.
 607
 608 config SYNTH_EVENTS
 609         bool "Synthetic trace events"
 610         select TRACING
 611         select DYNAMIC_EVENTS
 612         default n
 613         help
 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.
 619
 620           See Documentation/trace/events.rst or
 621           Documentation/trace/histogram.rst for details and examples.
 622
 623           If in doubt, say N.
 624
 625 config HIST_TRIGGERS
 626         bool "Histogram triggers"
 627         depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
 628         select TRACING_MAP
 629         select TRACING
 630         select DYNAMIC_EVENTS
 631         select SYNTH_EVENTS
 632         default n
 633         help
 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.
 640
 641           Inter-event tracing of quantities such as latencies is also
 642           supported using hist triggers under this option.
 643
 644           See Documentation/trace/histogram.rst.
 645           If in doubt, say N.
 646
 647 config TRACE_EVENT_INJECT
 648         bool "Trace event injection"
 649         depends on TRACING
 650         help
 651           Allow user-space to inject a specific trace event into the ring
 652           buffer. This is mainly used for testing purpose.
 653
 654           If unsure, say N.
 655
 656 config TRACEPOINT_BENCHMARK
 657         bool "Add tracepoint that benchmarks tracepoints"
 658         help
 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.
 670
 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.
 673
 674          An example of the output:
 675
 676               START
 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
 684
 685
 686 config RING_BUFFER_BENCHMARK
 687         tristate "Ring buffer benchmark stress tester"
 688         depends on RING_BUFFER
 689         help
 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.
 696
 697           It does not disable interrupts or raise its priority, so it may be
 698           affected by processes that are running.
 699
 700           If unsure, say N.
 701
 702 config TRACE_EVAL_MAP_FILE
 703        bool "Show eval mappings for trace events"
 704        depends on TRACING
 705        help
 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.
 710
 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.
 714
 715         If something does not get converted properly, this option can be
 716         used to show what enums/sizeof the kernel tried to convert.
 717
 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
 721         belong too.
 722
 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.
 727
 728         If unsure, say N.
 729
 730 config GCOV_PROFILE_FTRACE
 731         bool "Enable GCOV profiling on ftrace subsystem"
 732         depends on GCOV_KERNEL
 733         help
 734           Enable GCOV profiling on ftrace subsystem for checking
 735           which functions/lines are tested.
 736
 737           If unsure, say N.
 738
 739           Note that on a kernel compiled with this config, ftrace will
 740           run significantly slower.
 741
 742 config FTRACE_SELFTEST
 743         bool
 744
 745 config FTRACE_STARTUP_TEST
 746         bool "Perform a startup test on ftrace"
 747         depends on GENERIC_TRACER
 748         select FTRACE_SELFTEST
 749         help
 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
 753           tracers of ftrace.
 754
 755 config EVENT_TRACE_STARTUP_TEST
 756         bool "Run selftest on trace events"
 757         depends on FTRACE_STARTUP_TEST
 758         default y
 759         help
 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.
 764
 765 config EVENT_TRACE_TEST_SYSCALLS
 766         bool "Run selftest on syscall events"
 767         depends on EVENT_TRACE_STARTUP_TEST
 768         help
 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.
 773
 774          TBD - enable a way to actually call the syscalls as we test their
 775                events
 776
 777 config RING_BUFFER_STARTUP_TEST
 778        bool "Ring buffer startup self test"
 779        depends on RING_BUFFER
 780        help
 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.
 789
 790          The test runs for 10 seconds. This will slow your boot time
 791          by at least 10 more seconds.
 792
 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.
 797
 798          If unsure, say N
 799
 800 config MMIOTRACE_TEST
 801         tristate "Test module for mmiotrace"
 802         depends on MMIOTRACE && m
 803         help
 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.
 807
 808           Say N, unless you absolutely know what you are doing.
 809
 810 config PREEMPTIRQ_DELAY_TEST
 811         tristate "Test module to create a preempt / IRQ disable delay thread to test latency tracers"
 812         depends on m
 813         help
 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
 817           critical section.
 818
 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
 822
 823           If unsure, say N
 824
 825 config SYNTH_EVENT_GEN_TEST
 826         tristate "Test module for in-kernel synthetic event generation"
 827         depends on SYNTH_EVENTS
 828         help
 829           This option creates a test module to check the base
 830           functionality of in-kernel synthetic event definition and
 831           generation.
 832
 833           To test, insert the module, and then check the trace buffer
 834           for the generated sample events.
 835
 836           If unsure, say N.
 837
 838 config KPROBE_EVENT_GEN_TEST
 839         tristate "Test module for in-kernel kprobe event generation"
 840         depends on KPROBE_EVENTS
 841         help
 842           This option creates a test module to check the base
 843           functionality of in-kernel kprobe event definition.
 844
 845           To test, insert the module, and then check the trace buffer
 846           for the generated kprobe events.
 847
 848           If unsure, say N.
 849
 850 config HIST_TRIGGERS_DEBUG
 851         bool "Hist trigger debug support"
 852         depends on HIST_TRIGGERS
 853         help
 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.
 857
 858           The hist_debug file serves a couple of purposes:
 859
 860             - Helps developers verify that nothing is broken.
 861
 862             - Provides educational information to support the details
 863               of the hist trigger internals as described by
 864               Documentation/trace/histogram-design.rst.
 865
 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
 869           running histograms.
 870
 871           If unsure, say N.
 872
 873 endif # FTRACE
 874
 875 endif # TRACING_SUPPORT
 876