linux_kernel/kernel/trace/Kconfig

#
# Architectures that offer an FUNCTION_TRACER implementation should
#  select HAVE_FUNCTION_TRACER:
#

config USER_STACKTRACE_SUPPORT
	bool

config NOP_TRACER
	bool

config HAVE_FTRACE_NMI_ENTER
	bool
	help
	  See Documentation/trace/ftrace-design.rst

config HAVE_FUNCTION_TRACER
	bool
	help
	  See Documentation/trace/ftrace-design.rst

config HAVE_FUNCTION_GRAPH_TRACER
	bool
	help
	  See Documentation/trace/ftrace-design.rst

config HAVE_DYNAMIC_FTRACE
	bool
	help
	  See Documentation/trace/ftrace-design.rst

config HAVE_DYNAMIC_FTRACE_WITH_REGS
	bool

config HAVE_FTRACE_MCOUNT_RECORD
	bool
	help
	  See Documentation/trace/ftrace-design.rst

config HAVE_SYSCALL_TRACEPOINTS
	bool
	help
	  See Documentation/trace/ftrace-design.rst

config HAVE_FENTRY
	bool
	help
	  Arch supports the gcc options -pg with -mfentry

config HAVE_C_RECORDMCOUNT
	bool
	help
	  C version of recordmcount available?

config TRACER_MAX_TRACE
	bool

config TRACE_CLOCK
	bool

config RING_BUFFER
	bool
	select TRACE_CLOCK
	select IRQ_WORK

config FTRACE_NMI_ENTER
       bool
       depends on HAVE_FTRACE_NMI_ENTER
       default y

config EVENT_TRACING
	select CONTEXT_SWITCH_TRACER
        select GLOB
	bool

config CONTEXT_SWITCH_TRACER
	bool

config RING_BUFFER_ALLOW_SWAP
	bool
	help
	 Allow the use of ring_buffer_swap_cpu.
	 Adds a very slight overhead to tracing when enabled.

# All tracer options should select GENERIC_TRACER. For those options that are
# enabled by all tracers (context switch and event tracer) they select TRACING.
# This allows those options to appear when no other tracer is selected. But the
# options do not appear when something else selects it. We need the two options
# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
# hiding of the automatic options.

config TRACING
	bool
	select DEBUG_FS
	select RING_BUFFER
	select STACKTRACE if STACKTRACE_SUPPORT
	select TRACEPOINTS
	select NOP_TRACER
	select BINARY_PRINTF
	select EVENT_TRACING
	select TRACE_CLOCK

config GENERIC_TRACER
	bool
	select TRACING

#
# Minimum requirements an architecture has to meet for us to
# be able to offer generic tracing facilities:
#
config TRACING_SUPPORT
	bool
	depends on TRACE_IRQFLAGS_SUPPORT
	depends on STACKTRACE_SUPPORT
	default y

if TRACING_SUPPORT

menuconfig FTRACE
	bool "Tracers"
	default y if DEBUG_KERNEL
	help
	  Enable the kernel tracing infrastructure.

if FTRACE

config FUNCTION_TRACER
	bool "Kernel Function Tracer"
	depends on HAVE_FUNCTION_TRACER
	select KALLSYMS
	select GENERIC_TRACER
	select CONTEXT_SWITCH_TRACER
	select GLOB
	select TASKS_RCU if PREEMPT
	help
	  Enable the kernel to trace every kernel function. This is done
	  by using a compiler feature to insert a small, 5-byte No-Operation
	  instruction at the beginning of every kernel function, which NOP
	  sequence is then dynamically patched into a tracer call when
	  tracing is enabled by the administrator. If it's runtime disabled
	  (the bootup default), then the overhead of the instructions is very
	  small and not measurable even in micro-benchmarks.

config FUNCTION_GRAPH_TRACER
	bool "Kernel Function Graph Tracer"
	depends on HAVE_FUNCTION_GRAPH_TRACER
	depends on FUNCTION_TRACER
	depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
	default y
	help
	  Enable the kernel to trace a function at both its return
	  and its entry.
	  Its first purpose is to trace the duration of functions and
	  draw a call graph for each thread with some information like
	  the return value. This is done by setting the current return
	  address on the current task structure into a stack of calls.


config PREEMPTIRQ_EVENTS
	bool "Enable trace events for preempt and irq disable/enable"
	select TRACE_IRQFLAGS
	depends on DEBUG_PREEMPT || !PROVE_LOCKING
	depends on TRACING
	default n
	help
	  Enable tracing of disable and enable events for preemption and irqs.
	  For tracing preempt disable/enable events, DEBUG_PREEMPT must be
	  enabled. For tracing irq disable/enable events, PROVE_LOCKING must
	  be disabled.

config IRQSOFF_TRACER
	bool "Interrupts-off Latency Tracer"
	default n
	depends on TRACE_IRQFLAGS_SUPPORT
	depends on !ARCH_USES_GETTIMEOFFSET
	select TRACE_IRQFLAGS
	select GENERIC_TRACER
	select TRACER_MAX_TRACE
	select RING_BUFFER_ALLOW_SWAP
	select TRACER_SNAPSHOT
	select TRACER_SNAPSHOT_PER_CPU_SWAP
	help
	  This option measures the time spent in irqs-off critical
	  sections, with microsecond accuracy.

	  The default measurement method is a maximum search, which is
	  disabled by default and can be runtime (re-)started
	  via:

	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency

	  (Note that kernel size and overhead increase with this option
	  enabled. This option and the preempt-off timing option can be
	  used together or separately.)

config PREEMPT_TRACER
	bool "Preemption-off Latency Tracer"
	default n
	depends on !ARCH_USES_GETTIMEOFFSET
	depends on PREEMPT
	select GENERIC_TRACER
	select TRACER_MAX_TRACE
	select RING_BUFFER_ALLOW_SWAP
	select TRACER_SNAPSHOT
	select TRACER_SNAPSHOT_PER_CPU_SWAP
	help
	  This option measures the time spent in preemption-off critical
	  sections, with microsecond accuracy.

	  The default measurement method is a maximum search, which is
	  disabled by default and can be runtime (re-)started
	  via:

	      echo 0 > /sys/kernel/debug/tracing/tracing_max_latency

	  (Note that kernel size and overhead increase with this option
	  enabled. This option and the irqs-off timing option can be
	  used together or separately.)

config SCHED_TRACER
	bool "Scheduling Latency Tracer"
	select GENERIC_TRACER
	select CONTEXT_SWITCH_TRACER
	select TRACER_MAX_TRACE
	select TRACER_SNAPSHOT
	help
	  This tracer tracks the latency of the highest priority task
	  to be scheduled in, starting from the point it has woken up.

config HWLAT_TRACER
	bool "Tracer to detect hardware latencies (like SMIs)"
	select GENERIC_TRACER
	help
	 This tracer, when enabled will create one or more kernel threads,
	 depending on what the cpumask file is set to, which each thread
	 spinning in a loop looking for interruptions caused by
	 something other than the kernel. For example, if a
	 System Management Interrupt (SMI) takes a noticeable amount of
	 time, this tracer will detect it. This is useful for testing
	 if a system is reliable for Real Time tasks.

	 Some files are created in the tracing directory when this
	 is enabled:

	   hwlat_detector/width   - time in usecs for how long to spin for
	   hwlat_detector/window  - time in usecs between the start of each
				     iteration

	 A kernel thread is created that will spin with interrupts disabled
	 for "width" microseconds in every "window" cycle. It will not spin
	 for "window - width" microseconds, where the system can
	 continue to operate.

	 The output will appear in the trace and trace_pipe files.

	 When the tracer is not running, it has no affect on the system,
	 but when it is running, it can cause the system to be
	 periodically non responsive. Do not run this tracer on a
	 production system.

	 To enable this tracer, echo in "hwlat" into the current_tracer
	 file. Every time a latency is greater than tracing_thresh, it will
	 be recorded into the ring buffer.

config ENABLE_DEFAULT_TRACERS
	bool "Trace process context switches and events"
	depends on !GENERIC_TRACER
	select TRACING
	help
	  This tracer hooks to various trace points in the kernel,
	  allowing the user to pick and choose which trace point they
	  want to trace. It also includes the sched_switch tracer plugin.

config FTRACE_SYSCALLS
	bool "Trace syscalls"
	depends on HAVE_SYSCALL_TRACEPOINTS
	select GENERIC_TRACER
	select KALLSYMS
	help
	  Basic tracer to catch the syscall entry and exit events.

config TRACER_SNAPSHOT
	bool "Create a snapshot trace buffer"
	select TRACER_MAX_TRACE
	help
	  Allow tracing users to take snapshot of the current buffer using the
	  ftrace interface, e.g.:

	      echo 1 > /sys/kernel/debug/tracing/snapshot
	      cat snapshot

config TRACER_SNAPSHOT_PER_CPU_SWAP
        bool "Allow snapshot to swap per CPU"
	depends on TRACER_SNAPSHOT
	select RING_BUFFER_ALLOW_SWAP
	help
	  Allow doing a snapshot of a single CPU buffer instead of a
	  full swap (all buffers). If this is set, then the following is
	  allowed:

	      echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot

	  After which, only the tracing buffer for CPU 2 was swapped with
	  the main tracing buffer, and the other CPU buffers remain the same.

	  When this is enabled, this adds a little more overhead to the
	  trace recording, as it needs to add some checks to synchronize
	  recording with swaps. But this does not affect the performance
	  of the overall system. This is enabled by default when the preempt
	  or irq latency tracers are enabled, as those need to swap as well
	  and already adds the overhead (plus a lot more).

config TRACE_BRANCH_PROFILING
	bool
	select GENERIC_TRACER

choice
	prompt "Branch Profiling"
	default BRANCH_PROFILE_NONE
	help
	 The branch profiling is a software profiler. It will add hooks
	 into the C conditionals to test which path a branch takes.

	 The likely/unlikely profiler only looks at the conditions that
	 are annotated with a likely or unlikely macro.

	 The "all branch" profiler will profile every if-statement in the
	 kernel. This profiler will also enable the likely/unlikely
	 profiler.

	 Either of the above profilers adds a bit of overhead to the system.
	 If unsure, choose "No branch profiling".

config BRANCH_PROFILE_NONE
	bool "No branch profiling"
	help
	  No branch profiling. Branch profiling adds a bit of overhead.
	  Only enable it if you want to analyse the branching behavior.
	  Otherwise keep it disabled.

config PROFILE_ANNOTATED_BRANCHES
	bool "Trace likely/unlikely profiler"
	select TRACE_BRANCH_PROFILING
	help
	  This tracer profiles all likely and unlikely macros
	  in the kernel. It will display the results in:

	  /sys/kernel/debug/tracing/trace_stat/branch_annotated

	  Note: this will add a significant overhead; only turn this
	  on if you need to profile the system's use of these macros.

config PROFILE_ALL_BRANCHES
	bool "Profile all if conditionals" if !FORTIFY_SOURCE
	select TRACE_BRANCH_PROFILING
	help
	  This tracer profiles all branch conditions. Every if ()
	  taken in the kernel is recorded whether it hit or miss.
	  The results will be displayed in:

	  /sys/kernel/debug/tracing/trace_stat/branch_all

	  This option also enables the likely/unlikely profiler.

	  This configuration, when enabled, will impose a great overhead
	  on the system. This should only be enabled when the system
	  is to be analyzed in much detail.
endchoice

config TRACING_BRANCHES
	bool
	help
	  Selected by tracers that will trace the likely and unlikely
	  conditions. This prevents the tracers themselves from being
	  profiled. Profiling the tracing infrastructure can only happen
	  when the likelys and unlikelys are not being traced.

config BRANCH_TRACER
	bool "Trace likely/unlikely instances"
	depends on TRACE_BRANCH_PROFILING
	select TRACING_BRANCHES
	help
	  This traces the events of likely and unlikely condition
	  calls in the kernel.  The difference between this and the
	  "Trace likely/unlikely profiler" is that this is not a
	  histogram of the callers, but actually places the calling
	  events into a running trace buffer to see when and where the
	  events happened, as well as their results.

	  Say N if unsure.

config STACK_TRACER
	bool "Trace max stack"
	depends on HAVE_FUNCTION_TRACER
	select FUNCTION_TRACER
	select STACKTRACE
	select KALLSYMS
	help
	  This special tracer records the maximum stack footprint of the
	  kernel and displays it in /sys/kernel/debug/tracing/stack_trace.

	  This tracer works by hooking into every function call that the
	  kernel executes, and keeping a maximum stack depth value and
	  stack-trace saved.  If this is configured with DYNAMIC_FTRACE
	  then it will not have any overhead while the stack tracer
	  is disabled.

	  To enable the stack tracer on bootup, pass in 'stacktrace'
	  on the kernel command line.

	  The stack tracer can also be enabled or disabled via the
	  sysctl kernel.stack_tracer_enabled

	  Say N if unsure.

config BLK_DEV_IO_TRACE
	bool "Support for tracing block IO actions"
	depends on SYSFS
	depends on BLOCK
	select RELAY
	select DEBUG_FS
	select TRACEPOINTS
	select GENERIC_TRACER
	select STACKTRACE
	help
	  Say Y here if you want to be able to trace the block layer actions
	  on a given queue. Tracing allows you to see any traffic happening
	  on a block device queue. For more information (and the userspace
	  support tools needed), fetch the blktrace tools from:

	  git://git.kernel.dk/blktrace.git

	  Tracing also is possible using the ftrace interface, e.g.:

	    echo 1 > /sys/block/sda/sda1/trace/enable
	    echo blk > /sys/kernel/debug/tracing/current_tracer
	    cat /sys/kernel/debug/tracing/trace_pipe

	  If unsure, say N.

config KPROBE_EVENTS
	depends on KPROBES
	depends on HAVE_REGS_AND_STACK_ACCESS_API
	bool "Enable kprobes-based dynamic events"
	select TRACING
	select PROBE_EVENTS
	default y
	help
	  This allows the user to add tracing events (similar to tracepoints)
	  on the fly via the ftrace interface. See
	  Documentation/trace/kprobetrace.rst for more details.

	  Those events can be inserted wherever kprobes can probe, and record
	  various register and memory values.

	  This option is also required by perf-probe subcommand of perf tools.
	  If you want to use perf tools, this option is strongly recommended.

config UPROBE_EVENTS
	bool "Enable uprobes-based dynamic events"
	depends on ARCH_SUPPORTS_UPROBES
	depends on MMU
	depends on PERF_EVENTS
	select UPROBES
	select PROBE_EVENTS
	select TRACING
	default y
	help
	  This allows the user to add tracing events on top of userspace
	  dynamic events (similar to tracepoints) on the fly via the trace
	  events interface. Those events can be inserted wherever uprobes
	  can probe, and record various registers.
	  This option is required if you plan to use perf-probe subcommand
	  of perf tools on user space applications.

config BPF_EVENTS
	depends on BPF_SYSCALL
	depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
	bool
	default y
	help
	  This allows the user to attach BPF programs to kprobe events.

config PROBE_EVENTS
	def_bool n

config DYNAMIC_FTRACE
	bool "enable/disable function tracing dynamically"
	depends on FUNCTION_TRACER
	depends on HAVE_DYNAMIC_FTRACE
	default y
	help
	  This option will modify all the calls to function tracing
	  dynamically (will patch them out of the binary image and
	  replace them with a No-Op instruction) on boot up. During
	  compile time, a table is made of all the locations that ftrace
	  can function trace, and this table is linked into the kernel
	  image. When this is enabled, functions can be individually
	  enabled, and the functions not enabled will not affect
	  performance of the system.

	  See the files in /sys/kernel/debug/tracing:
	    available_filter_functions
	    set_ftrace_filter
	    set_ftrace_notrace

	  This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
	  otherwise has native performance as long as no tracing is active.

config DYNAMIC_FTRACE_WITH_REGS
	def_bool y
	depends on DYNAMIC_FTRACE
	depends on HAVE_DYNAMIC_FTRACE_WITH_REGS

config FUNCTION_PROFILER
	bool "Kernel function profiler"
	depends on FUNCTION_TRACER
	default n
	help
	  This option enables the kernel function profiler. A file is created
	  in debugfs called function_profile_enabled which defaults to zero.
	  When a 1 is echoed into this file profiling begins, and when a
	  zero is entered, profiling stops. A "functions" file is created in
	  the trace_stats directory; this file shows the list of functions that
	  have been hit and their counters.

	  If in doubt, say N.

config BPF_KPROBE_OVERRIDE
	bool "Enable BPF programs to override a kprobed function"
	depends on BPF_EVENTS
	depends on FUNCTION_ERROR_INJECTION
	default n
	help
	 Allows BPF to override the execution of a probed function and
	 set a different return value.  This is used for error injection.

config FTRACE_MCOUNT_RECORD
	def_bool y
	depends on DYNAMIC_FTRACE
	depends on HAVE_FTRACE_MCOUNT_RECORD

config FTRACE_SELFTEST
	bool

config FTRACE_STARTUP_TEST
	bool "Perform a startup test on ftrace"
	depends on GENERIC_TRACER
	select FTRACE_SELFTEST
	help
	  This option performs a series of startup tests on ftrace. On bootup
	  a series of tests are made to verify that the tracer is
	  functioning properly. It will do tests on all the configured
	  tracers of ftrace.

config EVENT_TRACE_TEST_SYSCALLS
	bool "Run selftest on syscall events"
	depends on FTRACE_STARTUP_TEST
	help
	 This option will also enable testing every syscall event.
	 It only enables the event and disables it and runs various loads
	 with the event enabled. This adds a bit more time for kernel boot
	 up since it runs this on every system call defined.

	 TBD - enable a way to actually call the syscalls as we test their
	       events

config MMIOTRACE
	bool "Memory mapped IO tracing"
	depends on HAVE_MMIOTRACE_SUPPORT && PCI
	select GENERIC_TRACER
	help
	  Mmiotrace traces Memory Mapped I/O access and is meant for
	  debugging and reverse engineering. It is called from the ioremap
	  implementation and works via page faults. Tracing is disabled by
	  default and can be enabled at run-time.

	  See Documentation/trace/mmiotrace.rst.
	  If you are not helping to develop drivers, say N.

config TRACING_MAP
	bool
	depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
	help
	  tracing_map is a special-purpose lock-free map for tracing,
	  separated out as a stand-alone facility in order to allow it
	  to be shared between multiple tracers.  It isn't meant to be
	  generally used outside of that context, and is normally
	  selected by tracers that use it.

config HIST_TRIGGERS
	bool "Histogram triggers"
	depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
	select TRACING_MAP
	select TRACING
	default n
	help
	  Hist triggers allow one or more arbitrary trace event fields
	  to be aggregated into hash tables and dumped to stdout by
	  reading a debugfs/tracefs file.  They're useful for
	  gathering quick and dirty (though precise) summaries of
	  event activity as an initial guide for further investigation
	  using more advanced tools.

	  Inter-event tracing of quantities such as latencies is also
	  supported using hist triggers under this option.

	  See Documentation/trace/histogram.txt.
	  If in doubt, say N.

config MMIOTRACE_TEST
	tristate "Test module for mmiotrace"
	depends on MMIOTRACE && m
	help
	  This is a dumb module for testing mmiotrace. It is very dangerous
	  as it will write garbage to IO memory starting at a given address.
	  However, it should be safe to use on e.g. unused portion of VRAM.

	  Say N, unless you absolutely know what you are doing.

config TRACEPOINT_BENCHMARK
        bool "Add tracepoint that benchmarks tracepoints"
	help
	 This option creates the tracepoint "benchmark:benchmark_event".
	 When the tracepoint is enabled, it kicks off a kernel thread that
	 goes into an infinite loop (calling cond_sched() to let other tasks
	 run), and calls the tracepoint. Each iteration will record the time
	 it took to write to the tracepoint and the next iteration that
	 data will be passed to the tracepoint itself. That is, the tracepoint
	 will report the time it took to do the previous tracepoint.
	 The string written to the tracepoint is a static string of 128 bytes
	 to keep the time the same. The initial string is simply a write of
	 "START". The second string records the cold cache time of the first
	 write which is not added to the rest of the calculations.

	 As it is a tight loop, it benchmarks as hot cache. That's fine because
	 we care most about hot paths that are probably in cache already.

	 An example of the output:

	      START
	      first=3672 [COLD CACHED]
	      last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
	      last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
	      last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
	      last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
	      last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
	      last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666


config RING_BUFFER_BENCHMARK
	tristate "Ring buffer benchmark stress tester"
	depends on RING_BUFFER
	help
	  This option creates a test to stress the ring buffer and benchmark it.
	  It creates its own ring buffer such that it will not interfere with
	  any other users of the ring buffer (such as ftrace). It then creates
	  a producer and consumer that will run for 10 seconds and sleep for
	  10 seconds. Each interval it will print out the number of events
	  it recorded and give a rough estimate of how long each iteration took.

	  It does not disable interrupts or raise its priority, so it may be
	  affected by processes that are running.

	  If unsure, say N.

config RING_BUFFER_STARTUP_TEST
       bool "Ring buffer startup self test"
       depends on RING_BUFFER
       help
         Run a simple self test on the ring buffer on boot up. Late in the
	 kernel boot sequence, the test will start that kicks off
	 a thread per cpu. Each thread will write various size events
	 into the ring buffer. Another thread is created to send IPIs
	 to each of the threads, where the IPI handler will also write
	 to the ring buffer, to test/stress the nesting ability.
	 If any anomalies are discovered, a warning will be displayed
	 and all ring buffers will be disabled.

	 The test runs for 10 seconds. This will slow your boot time
	 by at least 10 more seconds.

	 At the end of the test, statics and more checks are done.
	 It will output the stats of each per cpu buffer. What
	 was written, the sizes, what was read, what was lost, and
	 other similar details.

	 If unsure, say N

config TRACE_EVAL_MAP_FILE
       bool "Show eval mappings for trace events"
       depends on TRACING
       help
	The "print fmt" of the trace events will show the enum/sizeof names
	instead	of their values. This can cause problems for user space tools
	that use this string to parse the raw data as user space does not know
	how to convert the string to its value.

	To fix this, there's a special macro in the kernel that can be used
	to convert an enum/sizeof into its value. If this macro is used, then
	the print fmt strings will be converted to their values.

	If something does not get converted properly, this option can be
	used to show what enums/sizeof the kernel tried to convert.

	This option is for debugging the conversions. A file is created
	in the tracing directory called "eval_map" that will show the
	names matched with their values and what trace event system they
	belong too.

	Normally, the mapping of the strings to values will be freed after
	boot up or module load. With this option, they will not be freed, as
	they are needed for the "eval_map" file. Enabling this option will
	increase the memory footprint of the running kernel.

	If unsure, say N

config TRACING_EVENTS_GPIO
	bool "Trace gpio events"
	depends on GPIOLIB
	default y
	help
	  Enable tracing events for gpio subsystem

endif # FTRACE

endif # TRACING_SUPPORT