1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
|
#
# 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 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
|
