#
# Architectures that offer an FUNCTION_TRACER implementation should
# select HAVE_FUNCTION_TRACER:
#
config USER_STACKTRACE_SUPPORT
bool
config NOP_TRACER
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 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.
( 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_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 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
