[linux-block.git] / kernel / trace / Kconfig

#
# Architectures that offer an FTRACE implementation should select HAVE_FTRACE:
#
config HAVE_FTRACE
	bool

config TRACER_MAX_TRACE
	bool

config TRACING
	bool
	select DEBUG_FS

config FTRACE
	bool "Kernel Function Tracer"
	depends on DEBUG_KERNEL && HAVE_FTRACE
	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 IRQSOFF_TRACER
	bool "Interrupts-off Latency Tracer"
	default n
	depends on TRACE_IRQFLAGS_SUPPORT
	depends on GENERIC_TIME
	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
	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 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 DYNAMIC_FTRACE
	bool "enable/disable ftrace tracepoints dynamically"
	depends on FTRACE
	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_FTRACE 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.
Commit	Line	Data
16444a8a ACM	1	#
	2	# Architectures that offer an FTRACE implementation should select HAVE_FTRACE:
	3	#
	4	config HAVE_FTRACE
	5	bool
bc0c38d1	6
352ad25a SR	7	config TRACER_MAX_TRACE
	8	bool
	9
bc0c38d1 SR	10	config TRACING
	11	bool
	12	select DEBUG_FS
	13
1b29b018 SR	14	config FTRACE
	15	bool "Kernel Function Tracer"
	16	depends on DEBUG_KERNEL && HAVE_FTRACE
	17	select FRAME_POINTER
	18	select TRACING
35e8e302	19	select CONTEXT_SWITCH_TRACER
1b29b018 SR	20	help
	21	Enable the kernel to trace every kernel function. This is done
	22	by using a compiler feature to insert a small, 5-byte No-Operation
	23	instruction to the beginning of every kernel function, which NOP
	24	sequence is then dynamically patched into a tracer call when
	25	tracing is enabled by the administrator. If it's runtime disabled
	26	(the bootup default), then the overhead of the instructions is very
	27	small and not measurable even in micro-benchmarks.
35e8e302	28
81d68a96 SR	29	config IRQSOFF_TRACER
	30	bool "Interrupts-off Latency Tracer"
	31	default n
	32	depends on TRACE_IRQFLAGS_SUPPORT
	33	depends on GENERIC_TIME
	34	select TRACE_IRQFLAGS
	35	select TRACING
	36	select TRACER_MAX_TRACE
	37	help
	38	This option measures the time spent in irqs-off critical
	39	sections, with microsecond accuracy.
	40
	41	The default measurement method is a maximum search, which is
	42	disabled by default and can be runtime (re-)started
	43	via:
	44
	45	echo 0 > /debugfs/tracing/tracing_max_latency
	46
6cd8a4bb SR	47	(Note that kernel size and overhead increases with this option
	48	enabled. This option and the preempt-off timing option can be
	49	used together or separately.)
	50
	51	config PREEMPT_TRACER
	52	bool "Preemption-off Latency Tracer"
	53	default n
	54	depends on GENERIC_TIME
	55	depends on PREEMPT
	56	select TRACING
	57	select TRACER_MAX_TRACE
	58	help
	59	This option measures the time spent in preemption off critical
	60	sections, with microsecond accuracy.
	61
	62	The default measurement method is a maximum search, which is
	63	disabled by default and can be runtime (re-)started
	64	via:
	65
	66	echo 0 > /debugfs/tracing/tracing_max_latency
	67
	68	(Note that kernel size and overhead increases with this option
	69	enabled. This option and the irqs-off timing option can be
	70	used together or separately.)
	71
352ad25a SR	72	config SCHED_TRACER
	73	bool "Scheduling Latency Tracer"
	74	depends on DEBUG_KERNEL
	75	select TRACING
	76	select CONTEXT_SWITCH_TRACER
	77	select TRACER_MAX_TRACE
	78	help
	79	This tracer tracks the latency of the highest priority task
	80	to be scheduled in, starting from the point it has woken up.
	81
35e8e302 SR	82	config CONTEXT_SWITCH_TRACER
	83	bool "Trace process context switches"
	84	depends on DEBUG_KERNEL
	85	select TRACING
	86	select MARKERS
	87	help
	88	This tracer gets called from the context switch and records
	89	all switching of tasks.
	90
3d083395 SR	91	config DYNAMIC_FTRACE
	92	bool "enable/disable ftrace tracepoints dynamically"
	93	depends on FTRACE
	94	default y
	95	help
	96	This option will modify all the calls to ftrace dynamically
	97	(will patch them out of the binary image and replaces them
	98	with a No-Op instruction) as they are called. A table is
	99	created to dynamically enable them again.
	100
	101	This way a CONFIG_FTRACE kernel is slightly larger, but otherwise
	102	has native performance as long as no tracing is active.
	103
	104	The changes to the code are done by a kernel thread that
	105	wakes up once a second and checks to see if any ftrace calls
	106	were made. If so, it runs stop_machine (stops all CPUS)
	107	and modifies the code to jump over the call to ftrace.