tracing: profile likely and unlikely annotations

[net-next-2.6.git] / kernel / trace / Kconfig

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

config NOP_TRACER
	bool

config HAVE_FUNCTION_TRACER
	bool

config HAVE_FUNCTION_RET_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 TRACER_MAX_TRACE
	bool

config RING_BUFFER
	bool

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_RET_TRACER
	bool "Kernel Function return Tracer"
	depends on !DYNAMIC_FTRACE
	depends on HAVE_FUNCTION_RET_TRACER
	depends on FUNCTION_TRACER
	help
	  Enable the kernel to trace a function at its return.
	  It's first purpose is to trace the duration of functions.
	  This is done by setting the current return address on the thread
	  info structure of the current task.

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.

	  ( Note that tracing self tests can't be enabled if this tracer is
	    selected, because the self-tests are an initcall as well and that
	    would invalidate the boot trace. )

config TRACE_UNLIKELY_PROFILE
	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_likely
	  /debugfs/tracing/profile_unlikely

	  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 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. Because this logic has to execute in every
	  kernel function, all the time, this option can slow down the
	  kernel measurably and is generally intended for kernel
	  developers only.

	  Say N if unsure.

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 && !BOOT_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.

endmenu