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 default y 465 help 466 This allows the user to add tracing events (similar to tracepoints) 467 on the fly via the ftrace interface. See 468 Documentation/trace/kprobetrace.rst for more details. 469 470 Those events can be inserted wherever kprobes can probe, and record 471 various register and memory values. 472 473 This option is also required by perf-probe subcommand of perf tools. 474 If you want to use perf tools, this option is strongly recommended. 475 476config KPROBE_EVENTS_ON_NOTRACE 477 bool "Do NOT protect notrace function from kprobe events" 478 depends on KPROBE_EVENTS 479 depends on KPROBES_ON_FTRACE 480 default n 481 help 482 This is only for the developers who want to debug ftrace itself 483 using kprobe events. 484 485 If kprobes can use ftrace instead of breakpoint, ftrace related 486 functions are protected from kprobe-events to prevent an infinit 487 recursion or any unexpected execution path which leads to a kernel 488 crash. 489 490 This option disables such protection and allows you to put kprobe 491 events on ftrace functions for debugging ftrace by itself. 492 Note that this might let you shoot yourself in the foot. 493 494 If unsure, say N. 495 496config UPROBE_EVENTS 497 bool "Enable uprobes-based dynamic events" 498 depends on ARCH_SUPPORTS_UPROBES 499 depends on MMU 500 depends on PERF_EVENTS 501 select UPROBES 502 select PROBE_EVENTS 503 select TRACING 504 default y 505 help 506 This allows the user to add tracing events on top of userspace 507 dynamic events (similar to tracepoints) on the fly via the trace 508 events interface. Those events can be inserted wherever uprobes 509 can probe, and record various registers. 510 This option is required if you plan to use perf-probe subcommand 511 of perf tools on user space applications. 512 513config BPF_EVENTS 514 depends on BPF_SYSCALL 515 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS 516 bool 517 default y 518 help 519 This allows the user to attach BPF programs to kprobe events. 520 521config PROBE_EVENTS 522 def_bool n 523 524config DYNAMIC_FTRACE 525 bool "enable/disable function tracing dynamically" 526 depends on FUNCTION_TRACER 527 depends on HAVE_DYNAMIC_FTRACE 528 default y 529 help 530 This option will modify all the calls to function tracing 531 dynamically (will patch them out of the binary image and 532 replace them with a No-Op instruction) on boot up. During 533 compile time, a table is made of all the locations that ftrace 534 can function trace, and this table is linked into the kernel 535 image. When this is enabled, functions can be individually 536 enabled, and the functions not enabled will not affect 537 performance of the system. 538 539 See the files in /sys/kernel/debug/tracing: 540 available_filter_functions 541 set_ftrace_filter 542 set_ftrace_notrace 543 544 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but 545 otherwise has native performance as long as no tracing is active. 546 547config DYNAMIC_FTRACE_WITH_REGS 548 def_bool y 549 depends on DYNAMIC_FTRACE 550 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS 551 552config FUNCTION_PROFILER 553 bool "Kernel function profiler" 554 depends on FUNCTION_TRACER 555 default n 556 help 557 This option enables the kernel function profiler. A file is created 558 in debugfs called function_profile_enabled which defaults to zero. 559 When a 1 is echoed into this file profiling begins, and when a 560 zero is entered, profiling stops. A "functions" file is created in 561 the trace_stat directory; this file shows the list of functions that 562 have been hit and their counters. 563 564 If in doubt, say N. 565 566config BPF_KPROBE_OVERRIDE 567 bool "Enable BPF programs to override a kprobed function" 568 depends on BPF_EVENTS 569 depends on FUNCTION_ERROR_INJECTION 570 default n 571 help 572 Allows BPF to override the execution of a probed function and 573 set a different return value. This is used for error injection. 574 575config FTRACE_MCOUNT_RECORD 576 def_bool y 577 depends on DYNAMIC_FTRACE 578 depends on HAVE_FTRACE_MCOUNT_RECORD 579 580config FTRACE_SELFTEST 581 bool 582 583config FTRACE_STARTUP_TEST 584 bool "Perform a startup test on ftrace" 585 depends on GENERIC_TRACER 586 select FTRACE_SELFTEST 587 help 588 This option performs a series of startup tests on ftrace. On bootup 589 a series of tests are made to verify that the tracer is 590 functioning properly. It will do tests on all the configured 591 tracers of ftrace. 592 593config EVENT_TRACE_TEST_SYSCALLS 594 bool "Run selftest on syscall events" 595 depends on FTRACE_STARTUP_TEST 596 help 597 This option will also enable testing every syscall event. 598 It only enables the event and disables it and runs various loads 599 with the event enabled. This adds a bit more time for kernel boot 600 up since it runs this on every system call defined. 601 602 TBD - enable a way to actually call the syscalls as we test their 603 events 604 605config MMIOTRACE 606 bool "Memory mapped IO tracing" 607 depends on HAVE_MMIOTRACE_SUPPORT && PCI 608 select GENERIC_TRACER 609 help 610 Mmiotrace traces Memory Mapped I/O access and is meant for 611 debugging and reverse engineering. It is called from the ioremap 612 implementation and works via page faults. Tracing is disabled by 613 default and can be enabled at run-time. 614 615 See Documentation/trace/mmiotrace.rst. 616 If you are not helping to develop drivers, say N. 617 618config TRACING_MAP 619 bool 620 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG 621 help 622 tracing_map is a special-purpose lock-free map for tracing, 623 separated out as a stand-alone facility in order to allow it 624 to be shared between multiple tracers. It isn't meant to be 625 generally used outside of that context, and is normally 626 selected by tracers that use it. 627 628config HIST_TRIGGERS 629 bool "Histogram triggers" 630 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG 631 select TRACING_MAP 632 select TRACING 633 default n 634 help 635 Hist triggers allow one or more arbitrary trace event fields 636 to be aggregated into hash tables and dumped to stdout by 637 reading a debugfs/tracefs file. They're useful for 638 gathering quick and dirty (though precise) summaries of 639 event activity as an initial guide for further investigation 640 using more advanced tools. 641 642 Inter-event tracing of quantities such as latencies is also 643 supported using hist triggers under this option. 644 645 See Documentation/trace/histogram.rst. 646 If in doubt, say N. 647 648config MMIOTRACE_TEST 649 tristate "Test module for mmiotrace" 650 depends on MMIOTRACE && m 651 help 652 This is a dumb module for testing mmiotrace. It is very dangerous 653 as it will write garbage to IO memory starting at a given address. 654 However, it should be safe to use on e.g. unused portion of VRAM. 655 656 Say N, unless you absolutely know what you are doing. 657 658config TRACEPOINT_BENCHMARK 659 bool "Add tracepoint that benchmarks tracepoints" 660 help 661 This option creates the tracepoint "benchmark:benchmark_event". 662 When the tracepoint is enabled, it kicks off a kernel thread that 663 goes into an infinite loop (calling cond_sched() to let other tasks 664 run), and calls the tracepoint. Each iteration will record the time 665 it took to write to the tracepoint and the next iteration that 666 data will be passed to the tracepoint itself. That is, the tracepoint 667 will report the time it took to do the previous tracepoint. 668 The string written to the tracepoint is a static string of 128 bytes 669 to keep the time the same. The initial string is simply a write of 670 "START". The second string records the cold cache time of the first 671 write which is not added to the rest of the calculations. 672 673 As it is a tight loop, it benchmarks as hot cache. That's fine because 674 we care most about hot paths that are probably in cache already. 675 676 An example of the output: 677 678 START 679 first=3672 [COLD CACHED] 680 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712 681 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337 682 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064 683 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411 684 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389 685 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666 686 687 688config RING_BUFFER_BENCHMARK 689 tristate "Ring buffer benchmark stress tester" 690 depends on RING_BUFFER 691 help 692 This option creates a test to stress the ring buffer and benchmark it. 693 It creates its own ring buffer such that it will not interfere with 694 any other users of the ring buffer (such as ftrace). It then creates 695 a producer and consumer that will run for 10 seconds and sleep for 696 10 seconds. Each interval it will print out the number of events 697 it recorded and give a rough estimate of how long each iteration took. 698 699 It does not disable interrupts or raise its priority, so it may be 700 affected by processes that are running. 701 702 If unsure, say N. 703 704config RING_BUFFER_STARTUP_TEST 705 bool "Ring buffer startup self test" 706 depends on RING_BUFFER 707 help 708 Run a simple self test on the ring buffer on boot up. Late in the 709 kernel boot sequence, the test will start that kicks off 710 a thread per cpu. Each thread will write various size events 711 into the ring buffer. Another thread is created to send IPIs 712 to each of the threads, where the IPI handler will also write 713 to the ring buffer, to test/stress the nesting ability. 714 If any anomalies are discovered, a warning will be displayed 715 and all ring buffers will be disabled. 716 717 The test runs for 10 seconds. This will slow your boot time 718 by at least 10 more seconds. 719 720 At the end of the test, statics and more checks are done. 721 It will output the stats of each per cpu buffer. What 722 was written, the sizes, what was read, what was lost, and 723 other similar details. 724 725 If unsure, say N 726 727config PREEMPTIRQ_DELAY_TEST 728 tristate "Preempt / IRQ disable delay thread to test latency tracers" 729 depends on m 730 help 731 Select this option to build a test module that can help test latency 732 tracers by executing a preempt or irq disable section with a user 733 configurable delay. The module busy waits for the duration of the 734 critical section. 735 736 For example, the following invocation forces a one-time irq-disabled 737 critical section for 500us: 738 modprobe preemptirq_delay_test test_mode=irq delay=500000 739 740 If unsure, say N 741 742config TRACE_EVAL_MAP_FILE 743 bool "Show eval mappings for trace events" 744 depends on TRACING 745 help 746 The "print fmt" of the trace events will show the enum/sizeof names 747 instead of their values. This can cause problems for user space tools 748 that use this string to parse the raw data as user space does not know 749 how to convert the string to its value. 750 751 To fix this, there's a special macro in the kernel that can be used 752 to convert an enum/sizeof into its value. If this macro is used, then 753 the print fmt strings will be converted to their values. 754 755 If something does not get converted properly, this option can be 756 used to show what enums/sizeof the kernel tried to convert. 757 758 This option is for debugging the conversions. A file is created 759 in the tracing directory called "eval_map" that will show the 760 names matched with their values and what trace event system they 761 belong too. 762 763 Normally, the mapping of the strings to values will be freed after 764 boot up or module load. With this option, they will not be freed, as 765 they are needed for the "eval_map" file. Enabling this option will 766 increase the memory footprint of the running kernel. 767 768 If unsure, say N 769 770config TRACING_EVENTS_GPIO 771 bool "Trace gpio events" 772 depends on GPIOLIB 773 default y 774 help 775 Enable tracing events for gpio subsystem 776 777config GCOV_PROFILE_FTRACE 778 bool "Enable GCOV profiling on ftrace subsystem" 779 depends on GCOV_KERNEL 780 help 781 Enable GCOV profiling on ftrace subsystem for checking 782 which functions/lines are tested. 783 784 If unsure, say N. 785 786 Note that on a kernel compiled with this config, ftrace will 787 run significantly slower. 788 789endif # FTRACE 790 791endif # TRACING_SUPPORT 792 793