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_FTRACE_NMI_ENTER
  14         bool
  15         help
  16           See Documentation/trace/ftrace-design.rst
  17
  18 config HAVE_FUNCTION_TRACER
  19         bool
  20         help
  21           See Documentation/trace/ftrace-design.rst
  22
  23 config HAVE_FUNCTION_GRAPH_TRACER
  24         bool
  25         help
  26           See Documentation/trace/ftrace-design.rst
  27
  28 config HAVE_DYNAMIC_FTRACE
  29         bool
  30         help
  31           See Documentation/trace/ftrace-design.rst
  32
  33 config HAVE_DYNAMIC_FTRACE_WITH_REGS
  34         bool
  35
  36 config HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
  37         bool
  38
  39 config HAVE_FTRACE_MCOUNT_RECORD
  40         bool
  41         help
  42           See Documentation/trace/ftrace-design.rst
  43
  44 config HAVE_SYSCALL_TRACEPOINTS
  45         bool
  46         help
  47           See Documentation/trace/ftrace-design.rst
  48
  49 config HAVE_FENTRY
  50         bool
  51         help
  52           Arch supports the gcc options -pg with -mfentry
  53
  54 config HAVE_NOP_MCOUNT
  55         bool
  56         help
  57           Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
  58
  59 config HAVE_C_RECORDMCOUNT
  60         bool
  61         help
  62           C version of recordmcount available?
  63
  64 config TRACER_MAX_TRACE
  65         bool
  66
  67 config TRACE_CLOCK
  68         bool
  69
  70 config RING_BUFFER
  71         bool
  72         select TRACE_CLOCK
  73         select IRQ_WORK
  74
  75 config FTRACE_NMI_ENTER
  76        bool
  77        depends on HAVE_FTRACE_NMI_ENTER
  78        default y
  79
  80 config EVENT_TRACING
  81         select CONTEXT_SWITCH_TRACER
  82         select GLOB
  83         bool
  84
  85 config CONTEXT_SWITCH_TRACER
  86         bool
  87
  88 config RING_BUFFER_ALLOW_SWAP
  89         bool
  90         help
  91          Allow the use of ring_buffer_swap_cpu.
  92          Adds a very slight overhead to tracing when enabled.
  93
  94 config PREEMPTIRQ_TRACEPOINTS
  95         bool
  96         depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
  97         select TRACING
  98         default y
  99         help
 100           Create preempt/irq toggle tracepoints if needed, so that other parts
 101           of the kernel can use them to generate or add hooks to them.
 102
 103 # All tracer options should select GENERIC_TRACER. For those options that are
 104 # enabled by all tracers (context switch and event tracer) they select TRACING.
 105 # This allows those options to appear when no other tracer is selected. But the
 106 # options do not appear when something else selects it. We need the two options
 107 # GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
 108 # hiding of the automatic options.
 109
 110 config TRACING
 111         bool
 112         select RING_BUFFER
 113         select STACKTRACE if STACKTRACE_SUPPORT
 114         select TRACEPOINTS
 115         select NOP_TRACER
 116         select BINARY_PRINTF
 117         select EVENT_TRACING
 118         select TRACE_CLOCK
 119
 120 config GENERIC_TRACER
 121         bool
 122         select TRACING
 123
 124 #
 125 # Minimum requirements an architecture has to meet for us to
 126 # be able to offer generic tracing facilities:
 127 #
 128 config TRACING_SUPPORT
 129         bool
 130         depends on TRACE_IRQFLAGS_SUPPORT
 131         depends on STACKTRACE_SUPPORT
 132         default y
 133
 134 if TRACING_SUPPORT
 135
 136 menuconfig FTRACE
 137         bool "Tracers"
 138         default y if DEBUG_KERNEL
 139         help
 140           Enable the kernel tracing infrastructure.
 141
 142 if FTRACE
 143
 144 config BOOTTIME_TRACING
 145         bool "Boot-time Tracing support"
 146         depends on TRACING
 147         select BOOT_CONFIG
 148         help
 149           Enable developer to setup ftrace subsystem via supplemental
 150           kernel cmdline at boot time for debugging (tracing) driver
 151           initialization and boot process.
 152
 153 config FUNCTION_TRACER
 154         bool "Kernel Function Tracer"
 155         depends on HAVE_FUNCTION_TRACER
 156         select KALLSYMS
 157         select GENERIC_TRACER
 158         select CONTEXT_SWITCH_TRACER
 159         select GLOB
 160         select TASKS_RCU if PREEMPTION
 161         help
 162           Enable the kernel to trace every kernel function. This is done
 163           by using a compiler feature to insert a small, 5-byte No-Operation
 164           instruction at the beginning of every kernel function, which NOP
 165           sequence is then dynamically patched into a tracer call when
 166           tracing is enabled by the administrator. If it's runtime disabled
 167           (the bootup default), then the overhead of the instructions is very
 168           small and not measurable even in micro-benchmarks.
 169
 170 config FUNCTION_GRAPH_TRACER
 171         bool "Kernel Function Graph Tracer"
 172         depends on HAVE_FUNCTION_GRAPH_TRACER
 173         depends on FUNCTION_TRACER
 174         depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
 175         default y
 176         help
 177           Enable the kernel to trace a function at both its return
 178           and its entry.
 179           Its first purpose is to trace the duration of functions and
 180           draw a call graph for each thread with some information like
 181           the return value. This is done by setting the current return
 182           address on the current task structure into a stack of calls.
 183
 184 config DYNAMIC_FTRACE
 185         bool "enable/disable function tracing dynamically"
 186         depends on FUNCTION_TRACER
 187         depends on HAVE_DYNAMIC_FTRACE
 188         default y
 189         help
 190           This option will modify all the calls to function tracing
 191           dynamically (will patch them out of the binary image and
 192           replace them with a No-Op instruction) on boot up. During
 193           compile time, a table is made of all the locations that ftrace
 194           can function trace, and this table is linked into the kernel
 195           image. When this is enabled, functions can be individually
 196           enabled, and the functions not enabled will not affect
 197           performance of the system.
 198
 199           See the files in /sys/kernel/debug/tracing:
 200             available_filter_functions
 201             set_ftrace_filter
 202             set_ftrace_notrace
 203
 204           This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
 205           otherwise has native performance as long as no tracing is active.
 206
 207 config DYNAMIC_FTRACE_WITH_REGS
 208         def_bool y
 209         depends on DYNAMIC_FTRACE
 210         depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
 211
 212 config DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 213         def_bool y
 214         depends on DYNAMIC_FTRACE
 215         depends on HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
 216
 217 config FUNCTION_PROFILER
 218         bool "Kernel function profiler"
 219         depends on FUNCTION_TRACER
 220         default n
 221         help
 222           This option enables the kernel function profiler. A file is created
 223           in debugfs called function_profile_enabled which defaults to zero.
 224           When a 1 is echoed into this file profiling begins, and when a
 225           zero is entered, profiling stops. A "functions" file is created in
 226           the trace_stat directory; this file shows the list of functions that
 227           have been hit and their counters.
 228
 229           If in doubt, say N.
 230
 231 config STACK_TRACER
 232         bool "Trace max stack"
 233         depends on HAVE_FUNCTION_TRACER
 234         select FUNCTION_TRACER
 235         select STACKTRACE
 236         select KALLSYMS
 237         help
 238           This special tracer records the maximum stack footprint of the
 239           kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
 240
 241           This tracer works by hooking into every function call that the
 242           kernel executes, and keeping a maximum stack depth value and
 243           stack-trace saved.  If this is configured with DYNAMIC_FTRACE
 244           then it will not have any overhead while the stack tracer
 245           is disabled.
 246
 247           To enable the stack tracer on bootup, pass in 'stacktrace'
 248           on the kernel command line.
 249
 250           The stack tracer can also be enabled or disabled via the
 251           sysctl kernel.stack_tracer_enabled
 252
 253           Say N if unsure.
 254
 255 config TRACE_PREEMPT_TOGGLE
 256         bool
 257         help
 258           Enables hooks which will be called when preemption is first disabled,
 259           and last enabled.
 260
 261 config PREEMPTIRQ_EVENTS
 262         bool "Enable trace events for preempt and irq disable/enable"
 263         select TRACE_IRQFLAGS
 264         select TRACE_PREEMPT_TOGGLE if PREEMPTION
 265         select GENERIC_TRACER
 266         default n
 267         help
 268           Enable tracing of disable and enable events for preemption and irqs.
 269
 270 config IRQSOFF_TRACER
 271         bool "Interrupts-off Latency Tracer"
 272         default n
 273         depends on TRACE_IRQFLAGS_SUPPORT
 274         depends on !ARCH_USES_GETTIMEOFFSET
 275         select TRACE_IRQFLAGS
 276         select GENERIC_TRACER
 277         select TRACER_MAX_TRACE
 278         select RING_BUFFER_ALLOW_SWAP
 279         select TRACER_SNAPSHOT
 280         select TRACER_SNAPSHOT_PER_CPU_SWAP
 281         help
 282           This option measures the time spent in irqs-off critical
 283           sections, with microsecond accuracy.
 284
 285           The default measurement method is a maximum search, which is
 286           disabled by default and can be runtime (re-)started
 287           via:
 288
 289               echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 290
 291           (Note that kernel size and overhead increase with this option
 292           enabled. This option and the preempt-off timing option can be
 293           used together or separately.)
 294
 295 config PREEMPT_TRACER
 296         bool "Preemption-off Latency Tracer"
 297         default n
 298         depends on !ARCH_USES_GETTIMEOFFSET
 299         depends on PREEMPTION
 300         select GENERIC_TRACER
 301         select TRACER_MAX_TRACE
 302         select RING_BUFFER_ALLOW_SWAP
 303         select TRACER_SNAPSHOT
 304         select TRACER_SNAPSHOT_PER_CPU_SWAP
 305         select TRACE_PREEMPT_TOGGLE
 306         help
 307           This option measures the time spent in preemption-off critical
 308           sections, with microsecond accuracy.
 309
 310           The default measurement method is a maximum search, which is
 311           disabled by default and can be runtime (re-)started
 312           via:
 313
 314               echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
 315
 316           (Note that kernel size and overhead increase with this option
 317           enabled. This option and the irqs-off timing option can be
 318           used together or separately.)
 319
 320 config SCHED_TRACER
 321         bool "Scheduling Latency Tracer"
 322         select GENERIC_TRACER
 323         select CONTEXT_SWITCH_TRACER
 324         select TRACER_MAX_TRACE
 325         select TRACER_SNAPSHOT
 326         help
 327           This tracer tracks the latency of the highest priority task
 328           to be scheduled in, starting from the point it has woken up.
 329
 330 config HWLAT_TRACER
 331         bool "Tracer to detect hardware latencies (like SMIs)"
 332         select GENERIC_TRACER
 333         help
 334          This tracer, when enabled will create one or more kernel threads,
 335          depending on what the cpumask file is set to, which each thread
 336          spinning in a loop looking for interruptions caused by
 337          something other than the kernel. For example, if a
 338          System Management Interrupt (SMI) takes a noticeable amount of
 339          time, this tracer will detect it. This is useful for testing
 340          if a system is reliable for Real Time tasks.
 341
 342          Some files are created in the tracing directory when this
 343          is enabled:
 344
 345            hwlat_detector/width   - time in usecs for how long to spin for
 346            hwlat_detector/window  - time in usecs between the start of each
 347                                      iteration
 348
 349          A kernel thread is created that will spin with interrupts disabled
 350          for "width" microseconds in every "window" cycle. It will not spin
 351          for "window - width" microseconds, where the system can
 352          continue to operate.
 353
 354          The output will appear in the trace and trace_pipe files.
 355
 356          When the tracer is not running, it has no affect on the system,
 357          but when it is running, it can cause the system to be
 358          periodically non responsive. Do not run this tracer on a
 359          production system.
 360
 361          To enable this tracer, echo in "hwlat" into the current_tracer
 362          file. Every time a latency is greater than tracing_thresh, it will
 363          be recorded into the ring buffer.
 364
 365 config MMIOTRACE
 366         bool "Memory mapped IO tracing"
 367         depends on HAVE_MMIOTRACE_SUPPORT && PCI
 368         select GENERIC_TRACER
 369         help
 370           Mmiotrace traces Memory Mapped I/O access and is meant for
 371           debugging and reverse engineering. It is called from the ioremap
 372           implementation and works via page faults. Tracing is disabled by
 373           default and can be enabled at run-time.
 374
 375           See Documentation/trace/mmiotrace.rst.
 376           If you are not helping to develop drivers, say N.
 377
 378 config ENABLE_DEFAULT_TRACERS
 379         bool "Trace process context switches and events"
 380         depends on !GENERIC_TRACER
 381         select TRACING
 382         help
 383           This tracer hooks to various trace points in the kernel,
 384           allowing the user to pick and choose which trace point they
 385           want to trace. It also includes the sched_switch tracer plugin.
 386
 387 config FTRACE_SYSCALLS
 388         bool "Trace syscalls"
 389         depends on HAVE_SYSCALL_TRACEPOINTS
 390         select GENERIC_TRACER
 391         select KALLSYMS
 392         help
 393           Basic tracer to catch the syscall entry and exit events.
 394
 395 config TRACER_SNAPSHOT
 396         bool "Create a snapshot trace buffer"
 397         select TRACER_MAX_TRACE
 398         help
 399           Allow tracing users to take snapshot of the current buffer using the
 400           ftrace interface, e.g.:
 401
 402               echo 1 > /sys/kernel/debug/tracing/snapshot
 403               cat snapshot
 404
 405 config TRACER_SNAPSHOT_PER_CPU_SWAP
 406         bool "Allow snapshot to swap per CPU"
 407         depends on TRACER_SNAPSHOT
 408         select RING_BUFFER_ALLOW_SWAP
 409         help
 410           Allow doing a snapshot of a single CPU buffer instead of a
 411           full swap (all buffers). If this is set, then the following is
 412           allowed:
 413
 414               echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
 415
 416           After which, only the tracing buffer for CPU 2 was swapped with
 417           the main tracing buffer, and the other CPU buffers remain the same.
 418
 419           When this is enabled, this adds a little more overhead to the
 420           trace recording, as it needs to add some checks to synchronize
 421           recording with swaps. But this does not affect the performance
 422           of the overall system. This is enabled by default when the preempt
 423           or irq latency tracers are enabled, as those need to swap as well
 424           and already adds the overhead (plus a lot more).
 425
 426 config TRACE_BRANCH_PROFILING
 427         bool
 428         select GENERIC_TRACER
 429
 430 choice
 431         prompt "Branch Profiling"
 432         default BRANCH_PROFILE_NONE
 433         help
 434          The branch profiling is a software profiler. It will add hooks
 435          into the C conditionals to test which path a branch takes.
 436
 437          The likely/unlikely profiler only looks at the conditions that
 438          are annotated with a likely or unlikely macro.
 439
 440          The "all branch" profiler will profile every if-statement in the
 441          kernel. This profiler will also enable the likely/unlikely
 442          profiler.
 443
 444          Either of the above profilers adds a bit of overhead to the system.
 445          If unsure, choose "No branch profiling".
 446
 447 config BRANCH_PROFILE_NONE
 448         bool "No branch profiling"
 449         help
 450           No branch profiling. Branch profiling adds a bit of overhead.
 451           Only enable it if you want to analyse the branching behavior.
 452           Otherwise keep it disabled.
 453
 454 config PROFILE_ANNOTATED_BRANCHES
 455         bool "Trace likely/unlikely profiler"
 456         select TRACE_BRANCH_PROFILING
 457         help
 458           This tracer profiles all likely and unlikely macros
 459           in the kernel. It will display the results in:
 460
 461           /sys/kernel/debug/tracing/trace_stat/branch_annotated
 462
 463           Note: this will add a significant overhead; only turn this
 464           on if you need to profile the system's use of these macros.
 465
 466 config PROFILE_ALL_BRANCHES
 467         bool "Profile all if conditionals" if !FORTIFY_SOURCE
 468         select TRACE_BRANCH_PROFILING
 469         help
 470           This tracer profiles all branch conditions. Every if ()
 471           taken in the kernel is recorded whether it hit or miss.
 472           The results will be displayed in:
 473
 474           /sys/kernel/debug/tracing/trace_stat/branch_all
 475
 476           This option also enables the likely/unlikely profiler.
 477
 478           This configuration, when enabled, will impose a great overhead
 479           on the system. This should only be enabled when the system
 480           is to be analyzed in much detail.
 481 endchoice
 482
 483 config TRACING_BRANCHES
 484         bool
 485         help
 486           Selected by tracers that will trace the likely and unlikely
 487           conditions. This prevents the tracers themselves from being
 488           profiled. Profiling the tracing infrastructure can only happen
 489           when the likelys and unlikelys are not being traced.
 490
 491 config BRANCH_TRACER
 492         bool "Trace likely/unlikely instances"
 493         depends on TRACE_BRANCH_PROFILING
 494         select TRACING_BRANCHES
 495         help
 496           This traces the events of likely and unlikely condition
 497           calls in the kernel.  The difference between this and the
 498           "Trace likely/unlikely profiler" is that this is not a
 499           histogram of the callers, but actually places the calling
 500           events into a running trace buffer to see when and where the
 501           events happened, as well as their results.
 502
 503           Say N if unsure.
 504
 505 config BLK_DEV_IO_TRACE
 506         bool "Support for tracing block IO actions"
 507         depends on SYSFS
 508         depends on BLOCK
 509         select RELAY
 510         select DEBUG_FS
 511         select TRACEPOINTS
 512         select GENERIC_TRACER
 513         select STACKTRACE
 514         help
 515           Say Y here if you want to be able to trace the block layer actions
 516           on a given queue. Tracing allows you to see any traffic happening
 517           on a block device queue. For more information (and the userspace
 518           support tools needed), fetch the blktrace tools from:
 519
 520           git://git.kernel.dk/blktrace.git
 521
 522           Tracing also is possible using the ftrace interface, e.g.:
 523
 524             echo 1 > /sys/block/sda/sda1/trace/enable
 525             echo blk > /sys/kernel/debug/tracing/current_tracer
 526             cat /sys/kernel/debug/tracing/trace_pipe
 527
 528           If unsure, say N.
 529
 530 config KPROBE_EVENTS
 531         depends on KPROBES
 532         depends on HAVE_REGS_AND_STACK_ACCESS_API
 533         bool "Enable kprobes-based dynamic events"
 534         select TRACING
 535         select PROBE_EVENTS
 536         select DYNAMIC_EVENTS
 537         default y
 538         help
 539           This allows the user to add tracing events (similar to tracepoints)
 540           on the fly via the ftrace interface. See
 541           Documentation/trace/kprobetrace.rst for more details.
 542
 543           Those events can be inserted wherever kprobes can probe, and record
 544           various register and memory values.
 545
 546           This option is also required by perf-probe subcommand of perf tools.
 547           If you want to use perf tools, this option is strongly recommended.
 548
 549 config KPROBE_EVENTS_ON_NOTRACE
 550         bool "Do NOT protect notrace function from kprobe events"
 551         depends on KPROBE_EVENTS
 552         depends on KPROBES_ON_FTRACE
 553         default n
 554         help
 555           This is only for the developers who want to debug ftrace itself
 556           using kprobe events.
 557
 558           If kprobes can use ftrace instead of breakpoint, ftrace related
 559           functions are protected from kprobe-events to prevent an infinit
 560           recursion or any unexpected execution path which leads to a kernel
 561           crash.
 562
 563           This option disables such protection and allows you to put kprobe
 564           events on ftrace functions for debugging ftrace by itself.
 565           Note that this might let you shoot yourself in the foot.
 566
 567           If unsure, say N.
 568
 569 config UPROBE_EVENTS
 570         bool "Enable uprobes-based dynamic events"
 571         depends on ARCH_SUPPORTS_UPROBES
 572         depends on MMU
 573         depends on PERF_EVENTS
 574         select UPROBES
 575         select PROBE_EVENTS
 576         select DYNAMIC_EVENTS
 577         select TRACING
 578         default y
 579         help
 580           This allows the user to add tracing events on top of userspace
 581           dynamic events (similar to tracepoints) on the fly via the trace
 582           events interface. Those events can be inserted wherever uprobes
 583           can probe, and record various registers.
 584           This option is required if you plan to use perf-probe subcommand
 585           of perf tools on user space applications.
 586
 587 config BPF_EVENTS
 588         depends on BPF_SYSCALL
 589         depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
 590         bool
 591         default y
 592         help
 593           This allows the user to attach BPF programs to kprobe, uprobe, and
 594           tracepoint events.
 595
 596 config DYNAMIC_EVENTS
 597         def_bool n
 598
 599 config PROBE_EVENTS
 600         def_bool n
 601
 602 config BPF_KPROBE_OVERRIDE
 603         bool "Enable BPF programs to override a kprobed function"
 604         depends on BPF_EVENTS
 605         depends on FUNCTION_ERROR_INJECTION
 606         default n
 607         help
 608          Allows BPF to override the execution of a probed function and
 609          set a different return value.  This is used for error injection.
 610
 611 config FTRACE_MCOUNT_RECORD
 612         def_bool y
 613         depends on DYNAMIC_FTRACE
 614         depends on HAVE_FTRACE_MCOUNT_RECORD
 615
 616 config TRACING_MAP
 617         bool
 618         depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
 619         help
 620           tracing_map is a special-purpose lock-free map for tracing,
 621           separated out as a stand-alone facility in order to allow it
 622           to be shared between multiple tracers.  It isn't meant to be
 623           generally used outside of that context, and is normally
 624           selected by tracers that use it.
 625
 626 config HIST_TRIGGERS
 627         bool "Histogram triggers"
 628         depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
 629         select TRACING_MAP
 630         select TRACING
 631         select DYNAMIC_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 HIST_TRIGGERS
 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 endif # FTRACE
 851
 852 endif # TRACING_SUPPORT
 853