1TRACE-CMD-RECORD(1)                                        TRACE-CMD-RECORD(1)
2
3
4

NAME

6       trace-cmd-record - record a trace from the Ftrace Linux internal tracer
7

SYNOPSIS

9       trace-cmd record [OPTIONS] [command]
10

DESCRIPTION

12       The trace-cmd(1) record command will set up the Ftrace Linux kernel
13       tracer to record the specified plugins or events that happen while the
14       command executes. If no command is given, then it will record until the
15       user hits Ctrl-C.
16
17       The record command of trace-cmd will set up the Ftrace tracer to start
18       tracing the various events or plugins that are given on the command
19       line. It will then create a number of tracing processes (one per CPU)
20       that will start recording from the kernel ring buffer straight into
21       temporary files. When the command is complete (or Ctrl-C is hit) all
22       the files will be combined into a trace.dat file that can later be read
23       (see trace-cmd-report(1)).
24

OPTIONS

26       -p tracer
27           Specify a tracer. Tracers usually do more than just trace an event.
28           Common tracers are: function, function_graph, preemptirqsoff,
29           irqsoff, preemptoff and wakeup. A tracer must be supported by the
30           running kernel. To see a list of available tracers, see
31           trace-cmd-list(1).
32
33       -e event
34           Specify an event to trace. Various static trace points have been
35           added to the Linux kernel. They are grouped by subsystem where you
36           can enable all events of a given subsystem or specify specific
37           events to be enabled. The event is of the format
38           "subsystem:event-name". You can also just specify the subsystem
39           without the :event-name or the event-name without the "subsystem:".
40           Using "-e sched_switch" will enable the "sched_switch" event where
41           as, "-e sched" will enable all events under the "sched" subsystem.
42
43               The 'event' can also contain glob expressions. That is, "*stat*" will
44               select all events (or subsystems) that have the characters "stat" in their
45               names.
46
47               The keyword 'all' can be used to enable all events.
48
49       -a
50           Every event that is being recorded has its output format file saved
51           in the output file to be able to display it later. But if other
52           events are enabled in the trace without trace-cmd’s knowledge, the
53           formats of those events will not be recorded and trace-cmd report
54           will not be able to display them. If this is the case, then specify
55           the -a option and the format for all events in the system will be
56           saved.
57
58       -T
59           Enable a stacktrace on each event. For example:
60
61                         <idle>-0     [003] 58549.289091: sched_switch:         kworker/0:1:0 [120] R ==> trace-cmd:2603 [120]
62                         <idle>-0     [003] 58549.289092: kernel_stack:         <stack trace>
63               => schedule (ffffffff814b260e)
64               => cpu_idle (ffffffff8100a38c)
65               => start_secondary (ffffffff814ab828)
66
67       --func-stack
68           Enable a stack trace on all functions. Note this is only applicable
69           for the "function" plugin tracer, and will only take effect if the
70           -l option is used and succeeds in limiting functions. If the
71           function tracer is not filtered, and the stack trace is enabled,
72           you can live lock the machine.
73
74       -f filter
75           Specify a filter for the previous event. This must come after a -e.
76           This will filter what events get recorded based on the content of
77           the event. Filtering is passed to the kernel directly so what
78           filtering is allowed may depend on what version of the kernel you
79           have. Basically, it will let you use C notation to check if an
80           event should be processed or not.
81
82               ==, >=, <=, >, <, &, |, && and ||
83
84           The above are usually safe to use to compare fields.
85
86       --no-filter
87           Do not filter out the trace-cmd threads. By default, the threads
88           are filtered out to not be traced by events. This option will have
89           the trace-cmd threads also be traced.
90
91       -R trigger
92           Specify a trigger for the previous event. This must come after a
93           -e. This will add a given trigger to the given event. To only
94           enable the trigger and not the event itself, then place the event
95           after the -v option.
96
97               See Documentation/trace/events.txt in the Linux kernel source for more
98               information on triggers.
99
100       -v
101           This will cause all events specified after it on the command line
102           to not be traced. This is useful for selecting a subsystem to be
103           traced but to leave out various events. For Example: "-e sched -v
104           -e "*stat\*"" will enable all events in the sched subsystem except
105           those that have "stat" in their names.
106
107               Note: the *-v* option was taken from the way grep(1) inverts the following
108               matches.
109
110       -F
111           This will filter only the executable that is given on the command
112           line. If no command is given, then it will filter itself (pretty
113           pointless). Using -F will let you trace only events that are caused
114           by the given command.
115
116       -P pid
117           Similar to -F but lets you specify a process ID to trace.
118
119       -c
120           Used with either -F (or -P if kernel supports it) to trace the
121           process' children too.
122
123       --user
124           Execute the specified command as given user.
125
126       -C clock
127           Set the trace clock to "clock".
128
129               Use trace-cmd(1) list -C to see what clocks are available.
130
131       -o output-file
132           By default, trace-cmd report will create a trace.dat file. You can
133           specify a different file to write to with the -o option.
134
135       -l function-name
136           This will limit the function and function_graph tracers to only
137           trace the given function name. More than one -l may be specified on
138           the command line to trace more than one function. The limited use
139           of glob expressions are also allowed. These are match* to only
140           filter functions that start with match.  *match to only filter
141           functions that end with match.  *match\* to only filter on
142           functions that contain match.
143
144       -g function-name
145           This option is for the function_graph plugin. It will graph the
146           given function. That is, it will only trace the function and all
147           functions that it calls. You can have more than one -g on the
148           command line.
149
150       -n function-name
151           This has the opposite effect of -l. The function given with the -n
152           option will not be traced. This takes precedence, that is, if you
153           include the same function for both -n and -l, it will not be
154           traced.
155
156       -d
157           Some tracer plugins enable the function tracer by default. Like the
158           latency tracers. This option prevents the function tracer from
159           being enabled at start up.
160
161       -D
162           The option -d will try to use the function-trace option to disable
163           the function tracer (if available), otherwise it defaults to the
164           proc file: /proc/sys/kernel/ftrace_enabled, but will not touch it
165           if the function-trace option is available. The -D option will
166           disable both the ftrace_enabled proc file as well as the
167           function-trace option if it exists.
168
169               Note, this disable function tracing for all users, which includes users
170               outside of ftrace tracers (stack_tracer, perf, etc).
171
172       -O option
173           Ftrace has various options that can be enabled or disabled. This
174           allows you to set them. Appending the text no to an option disables
175           it. For example: "-O nograph-time" will disable the "graph-time"
176           Ftrace option.
177
178       -s interval
179           The processes that trace-cmd creates to record from the ring buffer
180           need to wake up to do the recording. Setting the interval to zero
181           will cause the processes to wakeup every time new data is written
182           into the buffer. But since Ftrace is recording kernel activity, the
183           act of this processes going back to sleep may cause new events into
184           the ring buffer which will wake the process back up. This will
185           needlessly add extra data into the ring buffer.
186
187               The 'interval' metric is microseconds. The default is set to 1000 (1 ms).
188               This is the time each recording process will sleep before waking up to
189               record any new data that was written to the ring buffer.
190
191       -r priority
192           The priority to run the capture threads at. In a busy system the
193           trace capturing threads may be staved and events can be lost. This
194           increases the priority of those threads to the real time (FIFO)
195           priority. But use this option with care, it can also change the
196           behaviour of the system being traced.
197
198       -b size
199           This sets the ring buffer size to size kilobytes. Because the
200           Ftrace ring buffer is per CPU, this size is the size of each per
201           CPU ring buffer inside the kernel. Using "-b 10000" on a machine
202           with 4 CPUs will make Ftrace have a total buffer size of 40 Megs.
203
204       -B buffer-name
205           If the kernel supports multiple buffers, this will add a buffer
206           with the given name. If the buffer name already exists, that buffer
207           is just reset and will not be deleted at the end of record
208           execution. If the buffer is created, it will be removed at the end
209           of execution (unless the -k is set, or start command was used).
210
211               After a buffer name is stated, all events added after that will be
212               associated with that buffer. If no buffer is specified, or an event
213               is specified before a buffer name, it will be associated with the
214               main (toplevel) buffer.
215
216               trace-cmd record -e sched -B block -e block -B time -e timer sleep 1
217
218               The above is will enable all sched events in the main buffer. It will
219               then create a 'block' buffer instance and enable all block events within
220               that buffer. A 'time' buffer instance is created and all timer events
221               will be enabled for that event.
222
223       -m size
224           The max size in kilobytes that a per cpu buffer should be. Note,
225           due to rounding to page size, the number may not be totally
226           correct. Also, this is performed by switching between two buffers
227           that are half the given size thus the output may not be of the
228           given size even if much more was written.
229
230               Use this to prevent running out of diskspace for long runs.
231
232       -M cpumask
233           Set the cpumask for to trace. It only affects the last buffer
234           instance given. If supplied before any buffer instance, then it
235           affects the main buffer. The value supplied must be a hex number.
236
237               trace-cmd record -p function -M c -B events13 -e all -M 5
238
239               If the -M is left out, then the mask stays the same. To enable all
240               CPUs, pass in a value of '-1'.
241
242       -k
243           By default, when trace-cmd is finished tracing, it will reset the
244           buffers and disable all the tracing that it enabled. This option
245           keeps trace-cmd from disabling the tracer and reseting the buffer.
246           This option is useful for debugging trace-cmd.
247
248               Note: usually trace-cmd will set the "tracing_on" file back to what it
249               was before it was called. This option will leave that file set to zero.
250
251       -i
252           By default, if an event is listed that trace-cmd does not find, it
253           will exit with an error. This option will just ignore events that
254           are listed on the command line but are not found on the system.
255
256       -N host:port
257           If another machine is running "trace-cmd listen", this option is
258           used to have the data sent to that machine with UDP packets.
259           Instead of writing to an output file, the data is sent off to a
260           remote box. This is ideal for embedded machines with little
261           storage, or having a single machine that will keep all the data in
262           a single repository.
263
264               Note: This option is not supported with latency tracer plugins:
265                 wakeup, wakeup_rt, irqsoff, preemptoff and preemptirqsoff
266
267       -t
268           This option is used with -N, when there’s a need to send the live
269           data with TCP packets instead of UDP. Although TCP is not nearly as
270           fast as sending the UDP packets, but it may be needed if the
271           network is not that reliable, the amount of data is not that
272           intensive, and a guarantee is needed that all traced information is
273           transfered successfully.
274
275       -q | --quiet
276           For use with recording an application. Suppresses normal output
277           (except for errors) to allow only the application’s output to be
278           displayed.
279
280       --date
281           With the --date option, "trace-cmd" will write timestamps into the
282           trace buffer after it has finished recording. It will then map the
283           timestamp to gettimeofday which will allow wall time output from
284           the timestamps reading the created trace.dat file.
285
286       --max-graph-depth depth
287           Set the maximum depth the function_graph tracer will trace into a
288           function. A value of one will only show where userspace enters the
289           kernel but not any functions called in the kernel. The default is
290           zero, which means no limit.
291
292       --cmdlines-size size
293           Set the number of entries the kernel tracing file "saved_cmdlines"
294           can contain. This file is a circular buffer which stores the
295           mapping between cmdlines and PIDs. If full, it leads to unresolved
296           cmdlines ("<...>") within the trace. The kernel default value is
297           128.
298
299       --module module
300           Filter a module’s name in function tracing. It is equivalent to
301           adding :mod:module after all other functions being filtered. If no
302           other function filter is listed, then all modules functions will be
303           filtered in the filter.
304
305               '--module snd'  is equivalent to  '-l :mod:snd'
306
307               '--module snd -l "*jack*"' is equivalent to '-l "*jack*:mod:snd"'
308
309               '--module snd -n "*"' is equivalent to '-n :mod:snd'
310
311       --proc-map
312           Save the traced process address map into the trace.dat file. The
313           traced processes can be specified using the option -P, or as a
314           given command.
315
316       --profile
317           With the --profile option, "trace-cmd" will enable tracing that can
318           be used with trace-cmd-report(1) --profile option. If a tracer -p
319           is not set, and function graph depth is supported by the kernel,
320           then the function_graph tracer will be enabled with a depth of one
321           (only show where userspace enters into the kernel). It will also
322           enable various tracepoints with stack tracing such that the report
323           can show where tasks have been blocked for the longest time.
324
325               See trace-cmd-profile(1) for more details and examples.
326
327       -G
328           Set interrupt (soft and hard) events as global (associated to CPU
329           instead of tasks). Only works for --profile.
330
331       -H event-hooks
332           Add custom event matching to connect any two events together. When
333           not used with --profile, it will save the parameter and this will
334           be used by trace-cmd report --profile, too. That is:
335
336               trace-cmd record -H hrtimer_expire_entry,hrtimer/hrtimer_expire_exit,hrtimer,sp
337               trace-cmd report --profile
338
339               Will profile hrtimer_expire_entry and hrtimer_expire_ext times.
340
341               See trace-cmd-profile(1) for format.
342
343       -S
344           (for --profile only) Only enable the tracer or events speficied on
345           the command line. With this option, the function_graph tracer is
346           not enabled, nor are any events (like sched_switch), unless they
347           are specifically specified on the command line (i.e. -p function -e
348           sched_switch -e sched_wakeup)
349
350       --ts-offset offset
351           Add an offset for the timestamp in the trace.dat file. This will
352           add a offset option into the trace.dat file such that a trace-cmd
353           report will offset all the timestamps of the events by the given
354           offset. The offset is in raw units. That is, if the event
355           timestamps are in nanoseconds the offset will also be in
356           nanoseconds even if the displayed units are in microseconds.
357
358       --tsync-interval
359           Set the loop interval, in ms, for timestamps synchronization with
360           guests: If a negative number is specified, timestamps
361           synchronization is disabled If 0 is specified, no loop is performed
362           - timestamps offset is calculated only twice," at the beginning and
363           at the end of the trace. Timestamps synchronization with guests
364           works only if there is support for VSOCK.\n"
365
366       --stderr
367           Have output go to stderr instead of stdout, but the output of the
368           command executed will not be changed. This is useful if you want to
369           monitor the output of the command being executed, but not see the
370           output from trace-cmd.
371

EXAMPLES

373       The basic way to trace all events:
374
375            # trace-cmd record -e all ls > /dev/null
376            # trace-cmd report
377                  trace-cmd-13541 [003] 106260.693809: filemap_fault: address=0x128122 offset=0xce
378                  trace-cmd-13543 [001] 106260.693809: kmalloc: call_site=81128dd4 ptr=0xffff88003dd83800 bytes_req=768 bytes_alloc=1024 gfp_flags=GFP_KERNEL|GFP_ZERO
379                         ls-13545 [002] 106260.693809: kfree: call_site=810a7abb ptr=0x0
380                         ls-13545 [002] 106260.693818: sys_exit_write:       0x1
381
382       To use the function tracer with sched switch tracing:
383
384            # trace-cmd record -p function -e sched_switch ls > /dev/null
385            # trace-cmd report
386                         ls-13587 [002] 106467.860310: function: hrtick_start_fair <-- pick_next_task_fair
387                         ls-13587 [002] 106467.860313: sched_switch: prev_comm=trace-cmd prev_pid=13587 prev_prio=120 prev_state=R ==> next_comm=trace-cmd next_pid=13583 next_prio=120
388                  trace-cmd-13585 [001] 106467.860314: function: native_set_pte_at <-- __do_fault
389                  trace-cmd-13586 [003] 106467.860314: function:             up_read <-- do_page_fault
390                         ls-13587 [002] 106467.860317: function:             __phys_addr <-- schedule
391                  trace-cmd-13585 [001] 106467.860318: function: _raw_spin_unlock <-- __do_fault
392                         ls-13587 [002] 106467.860320: function: native_load_sp0 <-- __switch_to
393                  trace-cmd-13586 [003] 106467.860322: function: down_read_trylock <-- do_page_fault
394
395       Here is a nice way to find what interrupts have the highest latency:
396
397            # trace-cmd record -p function_graph -e irq_handler_entry  -l do_IRQ sleep 10
398            # trace-cmd report
399                     <idle>-0     [000] 157412.933969: funcgraph_entry:                  |  do_IRQ() {
400                     <idle>-0     [000] 157412.933974: irq_handler_entry:    irq=48 name=eth0
401                     <idle>-0     [000] 157412.934004: funcgraph_exit:       + 36.358 us |  }
402                     <idle>-0     [000] 157413.895004: funcgraph_entry:                  |  do_IRQ() {
403                     <idle>-0     [000] 157413.895011: irq_handler_entry:    irq=48 name=eth0
404                     <idle>-0     [000] 157413.895026: funcgraph_exit:                        + 24.014 us |  }
405                     <idle>-0     [000] 157415.891762: funcgraph_entry:                  |  do_IRQ() {
406                     <idle>-0     [000] 157415.891769: irq_handler_entry:    irq=48 name=eth0
407                     <idle>-0     [000] 157415.891784: funcgraph_exit:       + 22.928 us |  }
408                     <idle>-0     [000] 157415.934869: funcgraph_entry:                  |  do_IRQ() {
409                     <idle>-0     [000] 157415.934874: irq_handler_entry:    irq=48 name=eth0
410                     <idle>-0     [000] 157415.934906: funcgraph_exit:       + 37.512 us |  }
411                     <idle>-0     [000] 157417.888373: funcgraph_entry:                  |  do_IRQ() {
412                     <idle>-0     [000] 157417.888381: irq_handler_entry:    irq=48 name=eth0
413                     <idle>-0     [000] 157417.888398: funcgraph_exit:       + 25.943 us |  }
414
415       An example of the profile:
416
417            # trace-cmd record --profile sleep 1
418            # trace-cmd report --profile --comm sleep
419           task: sleep-21611
420             Event: sched_switch:R (1) Total: 99442 Avg: 99442 Max: 99442 Min:99442
421                <stack> 1 total:99442 min:99442 max:99442 avg=99442
422                  => ftrace_raw_event_sched_switch (0xffffffff8105f812)
423                  => __schedule (0xffffffff8150810a)
424                  => preempt_schedule (0xffffffff8150842e)
425                  => ___preempt_schedule (0xffffffff81273354)
426                  => cpu_stop_queue_work (0xffffffff810b03c5)
427                  => stop_one_cpu (0xffffffff810b063b)
428                  => sched_exec (0xffffffff8106136d)
429                  => do_execve_common.isra.27 (0xffffffff81148c89)
430                  => do_execve (0xffffffff811490b0)
431                  => SyS_execve (0xffffffff811492c4)
432                  => return_to_handler (0xffffffff8150e3c8)
433                  => stub_execve (0xffffffff8150c699)
434             Event: sched_switch:S (1) Total: 1000506680 Avg: 1000506680 Max: 1000506680 Min:1000506680
435                <stack> 1 total:1000506680 min:1000506680 max:1000506680 avg=1000506680
436                  => ftrace_raw_event_sched_switch (0xffffffff8105f812)
437                  => __schedule (0xffffffff8150810a)
438                  => schedule (0xffffffff815084b8)
439                  => do_nanosleep (0xffffffff8150b22c)
440                  => hrtimer_nanosleep (0xffffffff8108d647)
441                  => SyS_nanosleep (0xffffffff8108d72c)
442                  => return_to_handler (0xffffffff8150e3c8)
443                  => tracesys_phase2 (0xffffffff8150c304)
444             Event: sched_wakeup:21611 (1) Total: 30326 Avg: 30326 Max: 30326 Min:30326
445                <stack> 1 total:30326 min:30326 max:30326 avg=30326
446                  => ftrace_raw_event_sched_wakeup_template (0xffffffff8105f653)
447                  => ttwu_do_wakeup (0xffffffff810606eb)
448                  => ttwu_do_activate.constprop.124 (0xffffffff810607c8)
449                  => try_to_wake_up (0xffffffff8106340a)
450

SEE ALSO

452       trace-cmd(1), trace-cmd-report(1), trace-cmd-start(1),
453       trace-cmd-stop(1), trace-cmd-extract(1), trace-cmd-reset(1),
454       trace-cmd-split(1), trace-cmd-list(1), trace-cmd-listen(1),
455       trace-cmd-profile(1)
456

AUTHOR

458       Written by Steven Rostedt, <rostedt@goodmis.org[1]>
459

RESOURCES

461       git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git
462

COPYING

464       Copyright (C) 2010 Red Hat, Inc. Free use of this software is granted
465       under the terms of the GNU Public License (GPL).
466

NOTES

468        1. rostedt@goodmis.org
469           mailto:rostedt@goodmis.org
470
471
472
473                                  12/02/2020               TRACE-CMD-RECORD(1)
Impressum