tracing: handle unregistering the current tracer

[linux-2.6-block.git] / 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

config HAVE_FUNCTION_TRACER
	bool

config HAVE_FUNCTION_GRAPH_TRACER
	bool

config HAVE_FUNCTION_TRACE_MCOUNT_TEST
	bool
	help
	 This gets selected when the arch tests the function_trace_stop
	 variable at the mcount call site. Otherwise, this variable
	 is tested by the called function.

config HAVE_DYNAMIC_FTRACE
	bool

config HAVE_FTRACE_MCOUNT_RECORD
	bool

config HAVE_HW_BRANCH_TRACER
	bool

config TRACER_MAX_TRACE
	bool

config RING_BUFFER
	bool

config FTRACE_NMI_ENTER
       bool
       depends on HAVE_FTRACE_NMI_ENTER
       default y

config TRACING
	bool
	select DEBUG_FS
	select RING_BUFFER
	select STACKTRACE if STACKTRACE_SUPPORT
	select TRACEPOINTS
	select NOP_TRACER

menu "Tracers"

config FUNCTION_TRACER
	bool "Kernel Function Tracer"
	depends on HAVE_FUNCTION_TRACER
	depends on DEBUG_KERNEL
	select FRAME_POINTER
	select TRACING
	select CONTEXT_SWITCH_TRACER
	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 to 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
	default y
	help
	  Enable the kernel to trace a function at both its return
	  and its entry.
	  It's first purpose is to trace the duration of functions and
	  draw a call graph for each thread with some informations like
	  the return value.
	  This is done by setting the current return address on the current
	  task structure into a stack of calls.

config IRQSOFF_TRACER
	bool "Interrupts-off Latency Tracer"
	default n
	depends on TRACE_IRQFLAGS_SUPPORT
	depends on GENERIC_TIME
	depends on DEBUG_KERNEL
	select TRACE_IRQFLAGS
	select TRACING
	select TRACER_MAX_TRACE
	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 > /debugfs/tracing/tracing_max_latency

	  (Note that kernel size and overhead increases 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 GENERIC_TIME
	depends on PREEMPT
	depends on DEBUG_KERNEL
	select TRACING
	select TRACER_MAX_TRACE
	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 > /debugfs/tracing/tracing_max_latency

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

config SYSPROF_TRACER
	bool "Sysprof Tracer"
	depends on X86
	select TRACING
	help
	  This tracer provides the trace needed by the 'Sysprof' userspace
	  tool.

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

config CONTEXT_SWITCH_TRACER
	bool "Trace process context switches"
	depends on DEBUG_KERNEL
	select TRACING
	select MARKERS
	help
	  This tracer gets called from the context switch and records
	  all switching of tasks.

config BOOT_TRACER
	bool "Trace boot initcalls"
	depends on DEBUG_KERNEL
	select TRACING
	select CONTEXT_SWITCH_TRACER
	help
	  This tracer helps developers to optimize boot times: it records
	  the timings of the initcalls and traces key events and the identity
	  of tasks that can cause boot delays, such as context-switches.

	  Its aim is to be parsed by the /scripts/bootgraph.pl tool to
	  produce pretty graphics about boot inefficiencies, giving a visual
	  representation of the delays during initcalls - but the raw
	  /debug/tracing/trace text output is readable too.

	  You must pass in ftrace=initcall to the kernel command line
	  to enable this on bootup.

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

	  /debugfs/tracing/profile_annotated_branch

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

	  Say N if unsure.

config PROFILE_ALL_BRANCHES
	bool "Profile all if conditionals"
	depends on 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:

	  /debugfs/tracing/profile_branch

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

	  Say N if unsure.

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 POWER_TRACER
	bool "Trace power consumption behavior"
	depends on DEBUG_KERNEL
	depends on X86
	select TRACING
	help
	  This tracer helps developers to analyze and optimize the kernels
	  power management decisions, specifically the C-state and P-state
	  behavior.


config STACK_TRACER
	bool "Trace max stack"
	depends on HAVE_FUNCTION_TRACER
	depends on DEBUG_KERNEL
	select FUNCTION_TRACER
	select STACKTRACE
	help
	  This special tracer records the maximum stack footprint of the
	  kernel and displays it in debugfs/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 HW_BRANCH_TRACER
	depends on HAVE_HW_BRANCH_TRACER
	bool "Trace hw branches"
	select TRACING
	help
	  This tracer records all branches on the system in a circular
	  buffer giving access to the last N branches for each cpu.

config KMEMTRACE
	bool "Trace SLAB allocations"
	select TRACING
	help
	  kmemtrace provides tracing for slab allocator functions, such as
	  kmalloc, kfree, kmem_cache_alloc, kmem_cache_free etc.. Collected
	  data is then fed to the userspace application in order to analyse
	  allocation hotspots, internal fragmentation and so on, making it
	  possible to see how well an allocator performs, as well as debug
	  and profile kernel code.

	  This requires an userspace application to use. See
	  Documentation/vm/kmemtrace.txt for more information.

	  Saying Y will make the kernel somewhat larger and slower. However,
	  if you disable kmemtrace at run-time or boot-time, the performance
	  impact is minimal (depending on the arch the kernel is built for).

	  If unsure, say N.

config WORKQUEUE_TRACER
	bool "Trace workqueues"
	select TRACING
	help
	  The workqueue tracer provides some statistical informations
          about each cpu workqueue thread such as the number of the
          works inserted and executed since their creation. It can help
          to evaluate the amount of work each of them have to perform.
          For example it can help a developer to decide whether he should
          choose a per cpu workqueue instead of a singlethreaded one.

config BLK_DEV_IO_TRACE
	bool "Support for tracing block io actions"
	depends on SYSFS
	select RELAY
	select DEBUG_FS
	select TRACEPOINTS
	select TRACING
	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 DYNAMIC_FTRACE
	bool "enable/disable ftrace tracepoints dynamically"
	depends on FUNCTION_TRACER
	depends on HAVE_DYNAMIC_FTRACE
	depends on DEBUG_KERNEL
	default y
	help
         This option will modify all the calls to ftrace dynamically
	 (will patch them out of the binary image and replaces them
	 with a No-Op instruction) as they are called. A table is
	 created to dynamically enable them again.

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

	 The changes to the code are done by a kernel thread that
	 wakes up once a second and checks to see if any ftrace calls
	 were made. If so, it runs stop_machine (stops all CPUS)
	 and modifies the code to jump over the call to ftrace.

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 TRACING && DEBUG_KERNEL
	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 MMIOTRACE
	bool "Memory mapped IO tracing"
	depends on HAVE_MMIOTRACE_SUPPORT && DEBUG_KERNEL && PCI
	select TRACING
	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/tracers/mmiotrace.txt.
	  If you are not helping to develop drivers, 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.

endmenu