1# 2# Architectures that offer an FUNCTION_TRACER implementation should 3# select HAVE_FUNCTION_TRACER: 4# 5 6config USER_STACKTRACE_SUPPORT 7 bool 8 9config NOP_TRACER 10 bool 11 12config HAVE_FTRACE_NMI_ENTER 13 bool 14 help 15 See Documentation/trace/ftrace-design.rst 16 17config HAVE_FUNCTION_TRACER 18 bool 19 help 20 See Documentation/trace/ftrace-design.rst 21 22config HAVE_FUNCTION_GRAPH_TRACER 23 bool 24 help 25 See Documentation/trace/ftrace-design.rst 26 27config HAVE_DYNAMIC_FTRACE 28 bool 29 help 30 See Documentation/trace/ftrace-design.rst 31 32config HAVE_DYNAMIC_FTRACE_WITH_REGS 33 bool 34 35config HAVE_FTRACE_MCOUNT_RECORD 36 bool 37 help 38 See Documentation/trace/ftrace-design.rst 39 40config HAVE_SYSCALL_TRACEPOINTS 41 bool 42 help 43 See Documentation/trace/ftrace-design.rst 44 45config HAVE_FENTRY 46 bool 47 help 48 Arch supports the gcc options -pg with -mfentry 49 50config HAVE_NOP_MCOUNT 51 bool 52 help 53 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount 54 55config HAVE_C_RECORDMCOUNT 56 bool 57 help 58 C version of recordmcount available? 59 60config TRACER_MAX_TRACE 61 bool 62 63config TRACE_CLOCK 64 bool 65 66config RING_BUFFER 67 bool 68 select TRACE_CLOCK 69 select IRQ_WORK 70 71config FTRACE_NMI_ENTER 72 bool 73 depends on HAVE_FTRACE_NMI_ENTER 74 default y 75 76config EVENT_TRACING 77 select CONTEXT_SWITCH_TRACER 78 select GLOB 79 bool 80 81config CONTEXT_SWITCH_TRACER 82 bool 83 84config RING_BUFFER_ALLOW_SWAP 85 bool 86 help 87 Allow the use of ring_buffer_swap_cpu. 88 Adds a very slight overhead to tracing when enabled. 89 90config PREEMPTIRQ_TRACEPOINTS 91 bool 92 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS 93 select TRACING 94 default y 95 help 96 Create preempt/irq toggle tracepoints if needed, so that other parts 97 of the kernel can use them to generate or add hooks to them. 98 99# All tracer options should select GENERIC_TRACER. For those options that are 100# enabled by all tracers (context switch and event tracer) they select TRACING. 101# This allows those options to appear when no other tracer is selected. But the 102# options do not appear when something else selects it. We need the two options 103# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the 104# hiding of the automatic options. 105 106config TRACING 107 bool 108 select DEBUG_FS 109 select RING_BUFFER 110 select STACKTRACE if STACKTRACE_SUPPORT 111 select TRACEPOINTS 112 select NOP_TRACER 113 select BINARY_PRINTF 114 select EVENT_TRACING 115 select TRACE_CLOCK 116 117config GENERIC_TRACER 118 bool 119 select TRACING 120 121# 122# Minimum requirements an architecture has to meet for us to 123# be able to offer generic tracing facilities: 124# 125config TRACING_SUPPORT 126 bool 127 depends on TRACE_IRQFLAGS_SUPPORT 128 depends on STACKTRACE_SUPPORT 129 default y 130 131if TRACING_SUPPORT 132 133menuconfig FTRACE 134 bool "Tracers" 135 default y if DEBUG_KERNEL 136 help 137 Enable the kernel tracing infrastructure. 138 139if FTRACE 140 141config FUNCTION_TRACER 142 bool "Kernel Function Tracer" 143 depends on HAVE_FUNCTION_TRACER 144 select KALLSYMS 145 select GENERIC_TRACER 146 select CONTEXT_SWITCH_TRACER 147 select GLOB 148 select TASKS_RCU if PREEMPT 149 help 150 Enable the kernel to trace every kernel function. This is done 151 by using a compiler feature to insert a small, 5-byte No-Operation 152 instruction at the beginning of every kernel function, which NOP 153 sequence is then dynamically patched into a tracer call when 154 tracing is enabled by the administrator. If it's runtime disabled 155 (the bootup default), then the overhead of the instructions is very 156 small and not measurable even in micro-benchmarks. 157 158config FUNCTION_GRAPH_TRACER 159 bool "Kernel Function Graph Tracer" 160 depends on HAVE_FUNCTION_GRAPH_TRACER 161 depends on FUNCTION_TRACER 162 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE 163 default y 164 help 165 Enable the kernel to trace a function at both its return 166 and its entry. 167 Its first purpose is to trace the duration of functions and 168 draw a call graph for each thread with some information like 169 the return value. This is done by setting the current return 170 address on the current task structure into a stack of calls. 171 172config TRACE_PREEMPT_TOGGLE 173 bool 174 help 175 Enables hooks which will be called when preemption is first disabled, 176 and last enabled. 177 178config PREEMPTIRQ_EVENTS 179 bool "Enable trace events for preempt and irq disable/enable" 180 select TRACE_IRQFLAGS 181 select TRACE_PREEMPT_TOGGLE if PREEMPT 182 select GENERIC_TRACER 183 default n 184 help 185 Enable tracing of disable and enable events for preemption and irqs. 186 187config IRQSOFF_TRACER 188 bool "Interrupts-off Latency Tracer" 189 default n 190 depends on TRACE_IRQFLAGS_SUPPORT 191 depends on !ARCH_USES_GETTIMEOFFSET 192 select TRACE_IRQFLAGS 193 select GENERIC_TRACER 194 select TRACER_MAX_TRACE 195 select RING_BUFFER_ALLOW_SWAP 196 select TRACER_SNAPSHOT 197 select TRACER_SNAPSHOT_PER_CPU_SWAP 198 help 199 This option measures the time spent in irqs-off critical 200 sections, with microsecond accuracy. 201 202 The default measurement method is a maximum search, which is 203 disabled by default and can be runtime (re-)started 204 via: 205 206 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency 207 208 (Note that kernel size and overhead increase with this option 209 enabled. This option and the preempt-off timing option can be 210 used together or separately.) 211 212config PREEMPT_TRACER 213 bool "Preemption-off Latency Tracer" 214 default n 215 depends on !ARCH_USES_GETTIMEOFFSET 216 depends on PREEMPT 217 select GENERIC_TRACER 218 select TRACER_MAX_TRACE 219 select RING_BUFFER_ALLOW_SWAP 220 select TRACER_SNAPSHOT 221 select TRACER_SNAPSHOT_PER_CPU_SWAP 222 select TRACE_PREEMPT_TOGGLE 223 help 224 This option measures the time spent in preemption-off critical 225 sections, with microsecond accuracy. 226 227 The default measurement method is a maximum search, which is 228 disabled by default and can be runtime (re-)started 229 via: 230 231 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency 232 233 (Note that kernel size and overhead increase with this option 234 enabled. This option and the irqs-off timing option can be 235 used together or separately.) 236 237config SCHED_TRACER 238 bool "Scheduling Latency Tracer" 239 select GENERIC_TRACER 240 select CONTEXT_SWITCH_TRACER 241 select TRACER_MAX_TRACE 242 select TRACER_SNAPSHOT 243 help 244 This tracer tracks the latency of the highest priority task 245 to be scheduled in, starting from the point it has woken up. 246 247config HWLAT_TRACER 248 bool "Tracer to detect hardware latencies (like SMIs)" 249 select GENERIC_TRACER 250 help 251 This tracer, when enabled will create one or more kernel threads, 252 depending on what the cpumask file is set to, which each thread 253 spinning in a loop looking for interruptions caused by 254 something other than the kernel. For example, if a 255 System Management Interrupt (SMI) takes a noticeable amount of 256 time, this tracer will detect it. This is useful for testing 257 if a system is reliable for Real Time tasks. 258 259 Some files are created in the tracing directory when this 260 is enabled: 261 262 hwlat_detector/width - time in usecs for how long to spin for 263 hwlat_detector/window - time in usecs between the start of each 264 iteration 265 266 A kernel thread is created that will spin with interrupts disabled 267 for "width" microseconds in every "window" cycle. It will not spin 268 for "window - width" microseconds, where the system can 269 continue to operate. 270 271 The output will appear in the trace and trace_pipe files. 272 273 When the tracer is not running, it has no affect on the system, 274 but when it is running, it can cause the system to be 275 periodically non responsive. Do not run this tracer on a 276 production system. 277 278 To enable this tracer, echo in "hwlat" into the current_tracer 279 file. Every time a latency is greater than tracing_thresh, it will 280 be recorded into the ring buffer. 281 282config ENABLE_DEFAULT_TRACERS 283 bool "Trace process context switches and events" 284 depends on !GENERIC_TRACER 285 select TRACING 286 help 287 This tracer hooks to various trace points in the kernel, 288 allowing the user to pick and choose which trace point they 289 want to trace. It also includes the sched_switch tracer plugin. 290 291config FTRACE_SYSCALLS 292 bool "Trace syscalls" 293 depends on HAVE_SYSCALL_TRACEPOINTS 294 select GENERIC_TRACER 295 select KALLSYMS 296 help 297 Basic tracer to catch the syscall entry and exit events. 298 299config TRACER_SNAPSHOT 300 bool "Create a snapshot trace buffer" 301 select TRACER_MAX_TRACE 302 help 303 Allow tracing users to take snapshot of the current buffer using the 304 ftrace interface, e.g.: 305 306 echo 1 > /sys/kernel/debug/tracing/snapshot 307 cat snapshot 308 309config TRACER_SNAPSHOT_PER_CPU_SWAP 310 bool "Allow snapshot to swap per CPU" 311 depends on TRACER_SNAPSHOT 312 select RING_BUFFER_ALLOW_SWAP 313 help 314 Allow doing a snapshot of a single CPU buffer instead of a 315 full swap (all buffers). If this is set, then the following is 316 allowed: 317 318 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot 319 320 After which, only the tracing buffer for CPU 2 was swapped with 321 the main tracing buffer, and the other CPU buffers remain the same. 322 323 When this is enabled, this adds a little more overhead to the 324 trace recording, as it needs to add some checks to synchronize 325 recording with swaps. But this does not affect the performance 326 of the overall system. This is enabled by default when the preempt 327 or irq latency tracers are enabled, as those need to swap as well 328 and already adds the overhead (plus a lot more). 329 330config TRACE_BRANCH_PROFILING 331 bool 332 select GENERIC_TRACER 333 334choice 335 prompt "Branch Profiling" 336 default BRANCH_PROFILE_NONE 337 help 338 The branch profiling is a software profiler. It will add hooks 339 into the C conditionals to test which path a branch takes. 340 341 The likely/unlikely profiler only looks at the conditions that 342 are annotated with a likely or unlikely macro. 343 344 The "all branch" profiler will profile every if-statement in the 345 kernel. This profiler will also enable the likely/unlikely 346 profiler. 347 348 Either of the above profilers adds a bit of overhead to the system. 349 If unsure, choose "No branch profiling". 350 351config BRANCH_PROFILE_NONE 352 bool "No branch profiling" 353 help 354 No branch profiling. Branch profiling adds a bit of overhead. 355 Only enable it if you want to analyse the branching behavior. 356 Otherwise keep it disabled. 357 358config PROFILE_ANNOTATED_BRANCHES 359 bool "Trace likely/unlikely profiler" 360 select TRACE_BRANCH_PROFILING 361 help 362 This tracer profiles all likely and unlikely macros 363 in the kernel. It will display the results in: 364 365 /sys/kernel/debug/tracing/trace_stat/branch_annotated 366 367 Note: this will add a significant overhead; only turn this 368 on if you need to profile the system's use of these macros. 369 370config PROFILE_ALL_BRANCHES 371 bool "Profile all if conditionals" if !FORTIFY_SOURCE 372 select TRACE_BRANCH_PROFILING 373 help 374 This tracer profiles all branch conditions. Every if () 375 taken in the kernel is recorded whether it hit or miss. 376 The results will be displayed in: 377 378 /sys/kernel/debug/tracing/trace_stat/branch_all 379 380 This option also enables the likely/unlikely profiler. 381 382 This configuration, when enabled, will impose a great overhead 383 on the system. This should only be enabled when the system 384 is to be analyzed in much detail. 385endchoice 386 387config TRACING_BRANCHES 388 bool 389 help 390 Selected by tracers that will trace the likely and unlikely 391 conditions. This prevents the tracers themselves from being 392 profiled. Profiling the tracing infrastructure can only happen 393 when the likelys and unlikelys are not being traced. 394 395config BRANCH_TRACER 396 bool "Trace likely/unlikely instances" 397 depends on TRACE_BRANCH_PROFILING 398 select TRACING_BRANCHES 399 help 400 This traces the events of likely and unlikely condition 401 calls in the kernel. The difference between this and the 402 "Trace likely/unlikely profiler" is that this is not a 403 histogram of the callers, but actually places the calling 404 events into a running trace buffer to see when and where the 405 events happened, as well as their results. 406 407 Say N if unsure. 408 409config STACK_TRACER 410 bool "Trace max stack" 411 depends on HAVE_FUNCTION_TRACER 412 select FUNCTION_TRACER 413 select STACKTRACE 414 select KALLSYMS 415 help 416 This special tracer records the maximum stack footprint of the 417 kernel and displays it in /sys/kernel/debug/tracing/stack_trace. 418 419 This tracer works by hooking into every function call that the 420 kernel executes, and keeping a maximum stack depth value and 421 stack-trace saved. If this is configured with DYNAMIC_FTRACE 422 then it will not have any overhead while the stack tracer 423 is disabled. 424 425 To enable the stack tracer on bootup, pass in 'stacktrace' 426 on the kernel command line. 427 428 The stack tracer can also be enabled or disabled via the 429 sysctl kernel.stack_tracer_enabled 430 431 Say N if unsure. 432 433config BLK_DEV_IO_TRACE 434 bool "Support for tracing block IO actions" 435 depends on SYSFS 436 depends on BLOCK 437 select RELAY 438 select DEBUG_FS 439 select TRACEPOINTS 440 select GENERIC_TRACER 441 select STACKTRACE 442 help 443 Say Y here if you want to be able to trace the block layer actions 444 on a given queue. Tracing allows you to see any traffic happening 445 on a block device queue. For more information (and the userspace 446 support tools needed), fetch the blktrace tools from: 447 448 git://git.kernel.dk/blktrace.git 449 450 Tracing also is possible using the ftrace interface, e.g.: 451 452 echo 1 > /sys/block/sda/sda1/trace/enable 453 echo blk > /sys/kernel/debug/tracing/current_tracer 454 cat /sys/kernel/debug/tracing/trace_pipe 455 456 If unsure, say N. 457 458config KPROBE_EVENTS 459 depends on KPROBES 460 depends on HAVE_REGS_AND_STACK_ACCESS_API 461 bool "Enable kprobes-based dynamic events" 462 select TRACING 463 select PROBE_EVENTS 464 select DYNAMIC_EVENTS 465 default y 466 help 467 This allows the user to add tracing events (similar to tracepoints) 468 on the fly via the ftrace interface. See 469 Documentation/trace/kprobetrace.rst for more details. 470 471 Those events can be inserted wherever kprobes can probe, and record 472 various register and memory values. 473 474 This option is also required by perf-probe subcommand of perf tools. 475 If you want to use perf tools, this option is strongly recommended. 476 477config KPROBE_EVENTS_ON_NOTRACE 478 bool "Do NOT protect notrace function from kprobe events" 479 depends on KPROBE_EVENTS 480 depends on KPROBES_ON_FTRACE 481 default n 482 help 483 This is only for the developers who want to debug ftrace itself 484 using kprobe events. 485 486 If kprobes can use ftrace instead of breakpoint, ftrace related 487 functions are protected from kprobe-events to prevent an infinit 488 recursion or any unexpected execution path which leads to a kernel 489 crash. 490 491 This option disables such protection and allows you to put kprobe 492 events on ftrace functions for debugging ftrace by itself. 493 Note that this might let you shoot yourself in the foot. 494 495 If unsure, say N. 496 497config UPROBE_EVENTS 498 bool "Enable uprobes-based dynamic events" 499 depends on ARCH_SUPPORTS_UPROBES 500 depends on MMU 501 depends on PERF_EVENTS 502 select UPROBES 503 select PROBE_EVENTS 504 select TRACING 505 default y 506 help 507 This allows the user to add tracing events on top of userspace 508 dynamic events (similar to tracepoints) on the fly via the trace 509 events interface. Those events can be inserted wherever uprobes 510 can probe, and record various registers. 511 This option is required if you plan to use perf-probe subcommand 512 of perf tools on user space applications. 513 514config BPF_EVENTS 515 depends on BPF_SYSCALL 516 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS 517 bool 518 default y 519 help 520 This allows the user to attach BPF programs to kprobe events. 521 522config DYNAMIC_EVENTS 523 def_bool n 524 525config PROBE_EVENTS 526 def_bool n 527 528config DYNAMIC_FTRACE 529 bool "enable/disable function tracing dynamically" 530 depends on FUNCTION_TRACER 531 depends on HAVE_DYNAMIC_FTRACE 532 default y 533 help 534 This option will modify all the calls to function tracing 535 dynamically (will patch them out of the binary image and 536 replace them with a No-Op instruction) on boot up. During 537 compile time, a table is made of all the locations that ftrace 538 can function trace, and this table is linked into the kernel 539 image. When this is enabled, functions can be individually 540 enabled, and the functions not enabled will not affect 541 performance of the system. 542 543 See the files in /sys/kernel/debug/tracing: 544 available_filter_functions 545 set_ftrace_filter 546 set_ftrace_notrace 547 548 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but 549 otherwise has native performance as long as no tracing is active. 550 551config DYNAMIC_FTRACE_WITH_REGS 552 def_bool y 553 depends on DYNAMIC_FTRACE 554 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS 555 556config FUNCTION_PROFILER 557 bool "Kernel function profiler" 558 depends on FUNCTION_TRACER 559 default n 560 help 561 This option enables the kernel function profiler. A file is created 562 in debugfs called function_profile_enabled which defaults to zero. 563 When a 1 is echoed into this file profiling begins, and when a 564 zero is entered, profiling stops. A "functions" file is created in 565 the trace_stat directory; this file shows the list of functions that 566 have been hit and their counters. 567 568 If in doubt, say N. 569 570config BPF_KPROBE_OVERRIDE 571 bool "Enable BPF programs to override a kprobed function" 572 depends on BPF_EVENTS 573 depends on FUNCTION_ERROR_INJECTION 574 default n 575 help 576 Allows BPF to override the execution of a probed function and 577 set a different return value. This is used for error injection. 578 579config FTRACE_MCOUNT_RECORD 580 def_bool y 581 depends on DYNAMIC_FTRACE 582 depends on HAVE_FTRACE_MCOUNT_RECORD 583 584config FTRACE_SELFTEST 585 bool 586 587config FTRACE_STARTUP_TEST 588 bool "Perform a startup test on ftrace" 589 depends on GENERIC_TRACER 590 select FTRACE_SELFTEST 591 help 592 This option performs a series of startup tests on ftrace. On bootup 593 a series of tests are made to verify that the tracer is 594 functioning properly. It will do tests on all the configured 595 tracers of ftrace. 596 597config EVENT_TRACE_TEST_SYSCALLS 598 bool "Run selftest on syscall events" 599 depends on FTRACE_STARTUP_TEST 600 help 601 This option will also enable testing every syscall event. 602 It only enables the event and disables it and runs various loads 603 with the event enabled. This adds a bit more time for kernel boot 604 up since it runs this on every system call defined. 605 606 TBD - enable a way to actually call the syscalls as we test their 607 events 608 609config MMIOTRACE 610 bool "Memory mapped IO tracing" 611 depends on HAVE_MMIOTRACE_SUPPORT && PCI 612 select GENERIC_TRACER 613 help 614 Mmiotrace traces Memory Mapped I/O access and is meant for 615 debugging and reverse engineering. It is called from the ioremap 616 implementation and works via page faults. Tracing is disabled by 617 default and can be enabled at run-time. 618 619 See Documentation/trace/mmiotrace.rst. 620 If you are not helping to develop drivers, say N. 621 622config TRACING_MAP 623 bool 624 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG 625 help 626 tracing_map is a special-purpose lock-free map for tracing, 627 separated out as a stand-alone facility in order to allow it 628 to be shared between multiple tracers. It isn't meant to be 629 generally used outside of that context, and is normally 630 selected by tracers that use it. 631 632config HIST_TRIGGERS 633 bool "Histogram triggers" 634 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG 635 select TRACING_MAP 636 select TRACING 637 default n 638 help 639 Hist triggers allow one or more arbitrary trace event fields 640 to be aggregated into hash tables and dumped to stdout by 641 reading a debugfs/tracefs file. They're useful for 642 gathering quick and dirty (though precise) summaries of 643 event activity as an initial guide for further investigation 644 using more advanced tools. 645 646 Inter-event tracing of quantities such as latencies is also 647 supported using hist triggers under this option. 648 649 See Documentation/trace/histogram.rst. 650 If in doubt, say N. 651 652config MMIOTRACE_TEST 653 tristate "Test module for mmiotrace" 654 depends on MMIOTRACE && m 655 help 656 This is a dumb module for testing mmiotrace. It is very dangerous 657 as it will write garbage to IO memory starting at a given address. 658 However, it should be safe to use on e.g. unused portion of VRAM. 659 660 Say N, unless you absolutely know what you are doing. 661 662config TRACEPOINT_BENCHMARK 663 bool "Add tracepoint that benchmarks tracepoints" 664 help 665 This option creates the tracepoint "benchmark:benchmark_event". 666 When the tracepoint is enabled, it kicks off a kernel thread that 667 goes into an infinite loop (calling cond_sched() to let other tasks 668 run), and calls the tracepoint. Each iteration will record the time 669 it took to write to the tracepoint and the next iteration that 670 data will be passed to the tracepoint itself. That is, the tracepoint 671 will report the time it took to do the previous tracepoint. 672 The string written to the tracepoint is a static string of 128 bytes 673 to keep the time the same. The initial string is simply a write of 674 "START". The second string records the cold cache time of the first 675 write which is not added to the rest of the calculations. 676 677 As it is a tight loop, it benchmarks as hot cache. That's fine because 678 we care most about hot paths that are probably in cache already. 679 680 An example of the output: 681 682 START 683 first=3672 [COLD CACHED] 684 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712 685 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337 686 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064 687 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411 688 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389 689 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666 690 691 692config RING_BUFFER_BENCHMARK 693 tristate "Ring buffer benchmark stress tester" 694 depends on RING_BUFFER 695 help 696 This option creates a test to stress the ring buffer and benchmark it. 697 It creates its own ring buffer such that it will not interfere with 698 any other users of the ring buffer (such as ftrace). It then creates 699 a producer and consumer that will run for 10 seconds and sleep for 700 10 seconds. Each interval it will print out the number of events 701 it recorded and give a rough estimate of how long each iteration took. 702 703 It does not disable interrupts or raise its priority, so it may be 704 affected by processes that are running. 705 706 If unsure, say N. 707 708config RING_BUFFER_STARTUP_TEST 709 bool "Ring buffer startup self test" 710 depends on RING_BUFFER 711 help 712 Run a simple self test on the ring buffer on boot up. Late in the 713 kernel boot sequence, the test will start that kicks off 714 a thread per cpu. Each thread will write various size events 715 into the ring buffer. Another thread is created to send IPIs 716 to each of the threads, where the IPI handler will also write 717 to the ring buffer, to test/stress the nesting ability. 718 If any anomalies are discovered, a warning will be displayed 719 and all ring buffers will be disabled. 720 721 The test runs for 10 seconds. This will slow your boot time 722 by at least 10 more seconds. 723 724 At the end of the test, statics and more checks are done. 725 It will output the stats of each per cpu buffer. What 726 was written, the sizes, what was read, what was lost, and 727 other similar details. 728 729 If unsure, say N 730 731config PREEMPTIRQ_DELAY_TEST 732 tristate "Preempt / IRQ disable delay thread to test latency tracers" 733 depends on m 734 help 735 Select this option to build a test module that can help test latency 736 tracers by executing a preempt or irq disable section with a user 737 configurable delay. The module busy waits for the duration of the 738 critical section. 739 740 For example, the following invocation forces a one-time irq-disabled 741 critical section for 500us: 742 modprobe preemptirq_delay_test test_mode=irq delay=500000 743 744 If unsure, say N 745 746config TRACE_EVAL_MAP_FILE 747 bool "Show eval mappings for trace events" 748 depends on TRACING 749 help 750 The "print fmt" of the trace events will show the enum/sizeof names 751 instead of their values. This can cause problems for user space tools 752 that use this string to parse the raw data as user space does not know 753 how to convert the string to its value. 754 755 To fix this, there's a special macro in the kernel that can be used 756 to convert an enum/sizeof into its value. If this macro is used, then 757 the print fmt strings will be converted to their values. 758 759 If something does not get converted properly, this option can be 760 used to show what enums/sizeof the kernel tried to convert. 761 762 This option is for debugging the conversions. A file is created 763 in the tracing directory called "eval_map" that will show the 764 names matched with their values and what trace event system they 765 belong too. 766 767 Normally, the mapping of the strings to values will be freed after 768 boot up or module load. With this option, they will not be freed, as 769 they are needed for the "eval_map" file. Enabling this option will 770 increase the memory footprint of the running kernel. 771 772 If unsure, say N 773 774config TRACING_EVENTS_GPIO 775 bool "Trace gpio events" 776 depends on GPIOLIB 777 default y 778 help 779 Enable tracing events for gpio subsystem 780 781config GCOV_PROFILE_FTRACE 782 bool "Enable GCOV profiling on ftrace subsystem" 783 depends on GCOV_KERNEL 784 help 785 Enable GCOV profiling on ftrace subsystem for checking 786 which functions/lines are tested. 787 788 If unsure, say N. 789 790 Note that on a kernel compiled with this config, ftrace will 791 run significantly slower. 792 793endif # FTRACE 794 795endif # TRACING_SUPPORT 796 797