doc/man/lttng.1

   1 .TH "LTTNG" "1" "February 9, 2012" "" ""
   2
   3 .SH "NAME"
   4 lttng \(em LTTng 2.0 tracer control command line tool
   5
   6 .SH "SYNOPSIS"
   7
   8 .PP
   9 .nf
  10 lttng [OPTIONS] <COMMAND>
  11 .fi
  12 .SH "DESCRIPTION"
  13
  14 .PP
  15 The LTTng project aims at providing highly efficient tracing tools for Linux.
  16 It's tracers help tracking down performance issues and debugging problems
  17 involving multiple concurrent processes and threads. Tracing across multiple
  18 systems is also possible.
  19
  20 The \fBlttng\fP command line tool from the lttng-tools package is used to control
  21 both kernel and user-space tracing. Every interactions with the tracer should
  22 be done by this tool or by the liblttng-ctl provided with the lttng-tools
  23 package.
  24
  25 LTTng uses a session daemon (lttng-sessiond(8)), acting as a tracing registry,
  26 which permits you to interact with multiple tracers (kernel and user-space)
  27 inside the same container, a tracing session. Traces can be gathered from the
  28 kernel and/or instrumented applications (lttng-ust(3)). Aggregating and reading
  29 those traces is done using the babeltrace(1) text viewer.
  30
  31 In order to trace the kernel, the session daemon needs to be running as root.
  32 LTTng provides the use of a \fBtracing group\fP (default: tracing). Whomever is
  33 in that group can interact with the root session daemon and thus trace the
  34 kernel. Session daemons can co-exist meaning that you can have a session daemon
  35 running as Alice that can be used to trace her applications along side with a
  36 root daemon or even a Bob daemon. We highly recommend to start the session
  37 daemon at boot time for stable and long term tracing.
  38
  39 Every user-space applications instrumented with lttng-ust(3), will
  40 automatically register to the session daemon. This feature gives you the
  41 ability to list available traceable applications and tracepoints on a per user
  42 basis. (See \fBlist\fP command).
  43 .SH "OPTIONS"
  44
  45 .PP
  46 This program follow the usual GNU command line syntax with long options starting with
  47 two dashes. Below is a summary of the available options.
  48 .PP
  49
  50 .TP
  51 .BR "\-h, \-\-help"
  52 Show summary of possible options and commands.
  53 .TP
  54 .BR "\-v, \-\-verbose"
  55 Increase verbosity.
  56 Three levels of verbosity are available which are triggered by putting additional v to
  57 the option (\-vv or \-vvv)
  58 .TP
  59 .BR "\-q, \-\-quiet"
  60 Suppress all messages (even errors).
  61 .TP
  62 .BR "\-g, \-\-group NAME"
  63 Set unix tracing group name. (default: tracing)
  64 .TP
  65 .BR "\-n, \-\-no-sessiond"
  66 Don't automatically spawn a session daemon.
  67 .TP
  68 .BR "\-\-sessiond\-path"
  69 Set session daemon full binary path.
  70 .TP
  71 .BR "\-\-list\-options"
  72 Simple listing of lttng options.
  73 .TP
  74 .BR "\-\-list\-commands"
  75 Simple listing of lttng commands.
  76 .SH "COMMANDS"
  77
  78 .TP
  79 \fBadd-context\fP
  80 .nf
  81 Add context to event(s) and/or channel(s).
  82
  83 A context is basically extra information appended to a channel or event. For
  84 instance, you could ask the tracer to add the PID information within the
  85 "sched_switch" kernel event. You can also add performance monitoring unit
  86 counters (perf PMU) using the perf kernel API).
  87
  88 For example, this command will add the context information 'prio' and two perf
  89 counters (hardware branch misses and cache misses), to all events in the trace
  90 data output:
  91
  92 # lttng add-context \-k \-t prio \-t perf:branch-misses \-t perf:cache-misses
  93
  94 Please take a look at the help (\-h/\-\-help) for a detailed list of available
  95 contexts.
  96
  97 If no channel and no event is given (\-c/\-e), the context is added to all
  98 channels (which applies automatically to all events in that channel). Otherwise
  99 the context will be added only to the channel (\-c) and/or event (\-e) indicated.
 100
 101 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 102 file.
 103 .fi
 104
 105 .B OPTIONS:
 106
 107 .nf
 108 \-h, \-\-help
 109         Show summary of possible options and commands.
 110 \-s, \-\-session NAME
 111         Apply on session name.
 112 \-c, \-\-channel NAME
 113         Apply on channel name.
 114 \-e, \-\-event NAME
 115         Apply on event name.
 116 \-k, \-\-kernel
 117         Apply for the kernel tracer
 118 \-u, \-\-userspace
 119         Apply for the user-space tracer
 120 \-t, \-\-type TYPE
 121         Context type. You can repeat this option on the command line. Please
 122         use "lttng add-context \-h" to list all available types.
 123 .fi
 124
 125 .IP
 126
 127 .IP "\fBcalibrate\fP"
 128 .nf
 129 Quantify LTTng overhead
 130
 131 The LTTng calibrate command can be used to find out the combined average
 132 overhead of the LTTng tracer and the instrumentation mechanisms used. This
 133 overhead can be calibrated in terms of time or using any of the PMU performance
 134 counter available on the system.
 135
 136 For now, the only calibration implemented is that of the kernel function
 137 instrumentation (kretprobes).
 138
 139 * Calibrate kernel function instrumentation
 140
 141 Let's use an example to show this calibration. We use an i7 processor with 4
 142 general-purpose PMU registers. This information is available by issuing dmesg,
 143 looking for "generic registers".
 144
 145 This sequence of commands will gather a trace executing a kretprobe hooked on
 146 an empty function, gathering PMU counters LLC (Last Level Cache) misses
 147 information (see lttng add-context \-\-help to see the list of available PMU
 148 counters).
 149
 150 # lttng create calibrate-function
 151 # lttng enable-event calibrate \-\-kernel \-\-function lttng_calibrate_kretprobe
 152 # lttng add-context \-\-kernel \-t perf:LLC-load-misses \-t perf:LLC-store-misses \\
 153                   \-t perf:LLC-prefetch-misses
 154 # lttng start
 155 # for a in $(seq 1 10); do \\
 156         lttng calibrate \-\-kernel \-\-function;
 157   done
 158 # lttng destroy
 159 # babeltrace $(ls \-1drt ~/lttng-traces/calibrate-function-* | tail \-n 1)
 160
 161 The output from babeltrace can be saved to a text file and opened in a
 162 spreadsheet (e.g. oocalc) to focus on the per-PMU counter delta between
 163 consecutive "calibrate_entry" and "calibrate_return" events. Note that these
 164 counters are per-CPU, so scheduling events would need to be present to account
 165 for migration between CPU. Therefore, for calibration purposes, only events
 166 staying on the same CPU must be considered.
 167
 168 The average result, for the i7, on 10 samples:
 169
 170                           Average     Std.Dev.
 171 perf_LLC_load_misses:       5.0       0.577
 172 perf_LLC_store_misses:      1.6       0.516
 173 perf_LLC_prefetch_misses:   9.0      14.742
 174
 175 As we can notice, the load and store misses are relatively stable across runs
 176 (their standard deviation is relatively low) compared to the prefetch misses.
 177 We can conclude from this information that LLC load and store misses can be
 178 accounted for quite precisely, but prefetches within a function seems to behave
 179 too erratically (not much causality link between the code executed and the CPU
 180 prefetch activity) to be accounted for.
 181 .fi
 182
 183 .B OPTIONS:
 184
 185 .nf
 186 \-h, \-\-help
 187         Show summary of possible options and commands.
 188 \-k, \-\-kernel
 189         Apply for the kernel tracer
 190 \-u, \-\-userspace
 191         Apply for the user-space tracer
 192 \-\-function
 193         Dynamic function entry/return probe (default)
 194 .fi
 195
 196 .IP
 197
 198 .IP "\fBcreate\fP [OPTIONS] [NAME]
 199 .nf
 200 Create tracing session.
 201
 202 A tracing session contains channel(s) which contains event(s). It is domain
 203 agnostic meaning that you can enable channels and events for either the
 204 user-space tracer and/or the kernel tracer. It acts like a container
 205 aggregating multiple tracing sources.
 206
 207 On creation, a \fB.lttngrc\fP file is created in your $HOME directory
 208 containing the current session name. If NAME is omitted, a session name is
 209 automatically created having this form: 'auto-yyyymmdd-hhmmss'.
 210
 211 If no \fB\-o, \-\-output\fP is specified, the traces will be written in
 212 $HOME/lttng-traces.
 213 .fi
 214
 215 .B OPTIONS:
 216
 217 .nf
 218 \-h, \-\-help
 219         Show summary of possible options and commands.
 220 \-\-list-options
 221         Simple listing of options
 222 \-o, \-\-output PATH
 223         Specify output path for traces
 224 .fi
 225
 226 .IP
 227
 228 .IP "\fBdestroy\fP [OPTIONS] [NAME]"
 229 .nf
 230 Teardown tracing session
 231
 232 Free memory on the session daemon and tracer side. It's gone!
 233
 234 If NAME is omitted, the session name is taken from the .lttngrc file.
 235 .fi
 236
 237 .B OPTIONS:
 238
 239 .nf
 240 \-h, \-\-help
 241         Show summary of possible options and commands.
 242 \-a, \-\-all
 243         Destroy all sessions
 244 \-\-list-options
 245         Simple listing of options
 246 .fi
 247
 248 .IP
 249
 250 .IP "\fBenable-channel\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
 251 .nf
 252 Enable tracing channel
 253
 254 To enable event, you must first enable a channel which contains event(s).
 255
 256 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 257 file.
 258 .fi
 259
 260 .B OPTIONS:
 261
 262 .nf
 263 \-h, \-\-help
 264         Show this help
 265 \-\-list-options
 266         Simple listing of options
 267 \-s, \-\-session
 268         Apply on session name
 269 \-k, \-\-kernel
 270         Apply to the kernel tracer
 271 \-u, \-\-userspace
 272         Apply to the user-space tracer
 273
 274 \-\-discard
 275         Discard event when subbuffers are full (default)
 276 \-\-overwrite
 277         Flight recorder mode : overwrites events when subbuffers are full
 278 \-\-subbuf-size
 279         Subbuffer size in bytes (default: 4096, kernel default: 262144)
 280 \-\-num-subbuf
 281         Number of subbuffers (default: 4)
 282         Needs to be a power of 2 for kernel and ust tracers
 283 \-\-switch-timer
 284         Switch subbuffer timer interval in usec (default: 0)
 285         Needs to be a power of 2 for kernel and ust tracers
 286 \-\-read-timer
 287         Read timer interval in usec (default: 200)
 288 .fi
 289
 290 .IP
 291
 292 .IP "\fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
 293 .nf
 294 Enable tracing event
 295
 296 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
 297 omitted, a default channel named '\fBchannel0\fP' is created and the event is
 298 added to it. For the user-space tracer, using \fB\-a, \-\-all\fP is the same as
 299 using the wildcard "*".
 300
 301 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 302 file.
 303 .fi
 304
 305 .B OPTIONS:
 306
 307 .nf
 308 \-h, \-\-help
 309         Show summary of possible options and commands.
 310 \-\-list-options
 311         Simple listing of options
 312 \-s, \-\-session
 313         Apply on session name
 314 \-c, \-\-channel
 315         Apply on channel name
 316 \-a, \-\-all
 317         Enable all tracepoints and syscalls
 318 \-k, \-\-kernel
 319         Apply for the kernel tracer
 320 \-u, \-\-userspace
 321         Apply for the user-space tracer
 322
 323 \-\-tracepoint
 324         Tracepoint event (default)
 325         - userspace tracer supports wildcards at end of string. Don't forget to
 326         quote to deal with bash expansion.
 327         e.g.:
 328         "*"
 329         "app_component:na*"
 330 \-\-loglevel
 331         Tracepoint loglevel
 332 \-\-probe [addr | symbol | symbol+offset]
 333         Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
 334         or hexadecimal (0xNNN...)
 335 \-\-function [addr | symbol | symbol+offset]
 336         Dynamic function entry/return probe. Addr and offset can be octal
 337         (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
 338 \-\-syscall
 339         System call event
 340         Enabling syscalls tracing (kernel tracer), you will not be able to disable them
 341         with disable-event. This is a known limitation. You can disable the entire
 342         channel to do the trick.
 343 \-\-filter 'expression'
 344         Set a filter on a newly enabled event.
 345         Filter expression on event fields event recording
 346         depends on evaluation. Only specify on first activation
 347         of a given event within a session. Filter only allowed
 348         when enabling events within a session before tracing is
 349         started.
 350 .fi
 351
 352 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
 353 .nf
 354 Disable tracing channel
 355
 356 Disabling a channel makes all event(s) in that channel to stop tracing. You can
 357 enable it back by calling \fBlttng enable-channel NAME\fP again.
 358
 359 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 360 file.
 361 .fi
 362
 363 .B OPTIONS:
 364
 365 .nf
 366 \-h, \-\-help
 367         Show summary of possible options and commands.
 368 \-\-list-options
 369         Simple listing of options
 370 \-s, \-\-session
 371         Apply on session name
 372 \-k, \-\-kernel
 373         Apply for the kernel tracer
 374 \-u, \-\-userspace
 375         Apply for the user-space tracer
 376 .fi
 377
 378 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
 379 .nf
 380 Disable tracing event
 381
 382 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
 383 NAME\fP again.
 384
 385 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 386 file.
 387 .fi
 388
 389 .B OPTIONS:
 390
 391 .nf
 392 \-h, \-\-help
 393         Show summary of possible options and commands.
 394 \-\-list-options
 395         Simple listing of options
 396 \-s, \-\-session
 397         Apply on session name
 398 \-k, \-\-kernel
 399         Apply for the kernel tracer
 400 \-u, \-\-userspace
 401         Apply for the user-space tracer
 402 .fi
 403
 404 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
 405 .nf
 406 List tracing session information.
 407
 408 With no arguments, it will list available tracing session(s).
 409
 410 With the session name, it will display the details of the session including
 411 the trace file path, the associated channels and their state (activated
 412 and deactivated), the activated events and more.
 413
 414 With \-k alone, it will list all available kernel events (except the system
 415 calls events).
 416 With \-u alone, it will list all available user-space events from registered
 417 applications. Here is an example of 'lttng list \-u':
 418
 419 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
 420       ust_tests_hello:tptest_sighandler (type: tracepoint)
 421       ust_tests_hello:tptest (type: tracepoint)
 422
 423 You can now enable any event listed by using the name :
 424 \fBust_tests_hello:tptest\fP.
 425 .fi
 426
 427 .B OPTIONS:
 428
 429 .nf
 430 \-h, \-\-help
 431         Show summary of possible options and commands.
 432 \-\-list-options
 433         Simple listing of options
 434 \-k, \-\-kernel
 435         Select kernel domain
 436 \-u, \-\-userspace
 437         Select user-space domain.
 438
 439 Session options:
 440 \-c, \-\-channel NAME
 441         List details of a channel
 442 \-d, \-\-domain
 443         List available domain(s)
 444 .fi
 445
 446 .IP "\fBset-session\fP NAME"
 447 .nf
 448 Set current session name
 449
 450 Will change the session name in the .lttngrc file.
 451 .fi
 452
 453 .B OPTIONS:
 454
 455 .nf
 456 \-h, \-\-help
 457         Show summary of possible options and commands.
 458 \-\-list-options
 459         Simple listing of options
 460 .fi
 461
 462 .IP
 463
 464 .IP "\fBstart\fP [OPTIONS] [NAME]"
 465 .nf
 466 Start tracing
 467
 468 It will start tracing for all tracers for a specific tracing session.
 469
 470 If NAME is omitted, the session name is taken from the .lttngrc file.
 471 .fi
 472
 473 .B OPTIONS:
 474
 475 .nf
 476 \-h, \-\-help
 477         Show summary of possible options and commands.
 478 \-\-list-options
 479         Simple listing of options
 480 .fi
 481
 482 .IP
 483
 484 .IP "\fBstop\fP [OPTIONS] [NAME]"
 485 .nf
 486 Stop tracing
 487
 488 It will stop tracing for all tracers for a specific tracing session.
 489
 490 If NAME is omitted, the session name is taken from the .lttngrc file.
 491 .fi
 492
 493 .B OPTIONS:
 494
 495 .nf
 496 \-h, \-\-help
 497         Show summary of possible options and commands.
 498 \-\-list-options
 499         Simple listing of options
 500 .fi
 501
 502 .IP
 503
 504 .IP "\fBversion\fP"
 505 .nf
 506 Show version information
 507 .fi
 508
 509 .B OPTIONS:
 510
 511 .nf
 512 \-h, \-\-help
 513         Show summary of possible options and commands.
 514 \-\-list-options
 515         Simple listing of options
 516 .fi
 517
 518 .IP
 519
 520 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
 521 .nf
 522 View traces of a tracing session
 523
 524 By default, the babeltrace viewer will be used for text viewing.
 525
 526 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
 527
 528 .fi
 529
 530 .B OPTIONS:
 531
 532 .nf
 533 \-h, \-\-help
 534         Show this help
 535 \-\-list-options
 536         Simple listing of options
 537 \-t, \-\-trace-path PATH
 538         Trace directory path for the viewer
 539 \-e, \-\-viewer CMD
 540         Specify viewer and/or options to use
 541         This will completely override the default viewers so
 542         please make sure to specify the full command. The trace
 543         directory path of the session will be appended at the end
 544         to the arguments
 545 .fi
 546
 547 .SH "EXIT VALUES"
 548
 549 .IP "0"
 550 Success
 551
 552 .IP "1"
 553 Command error
 554
 555 .IP "2"
 556 Undefined command
 557
 558 .IP "3"
 559 Fatal error
 560
 561 .IP "4"
 562 Command warning
 563
 564 .IP "16"
 565 No session found by the name given
 566
 567 .IP "18"
 568 Error in session creation
 569
 570 .IP "21"
 571 Error in application(s) listing
 572
 573 .IP "28"
 574 Session name already exists
 575
 576 .IP "33"
 577 Kernel tracer unavailable
 578
 579 .IP "35"
 580 Kernel event exists
 581
 582 .IP "37"
 583 Kernel channel exists
 584
 585 .IP "38"
 586 Kernel channel creation failed
 587
 588 .IP "39"
 589 Kernel channel not found
 590
 591 .IP "40"
 592 Kernel channel disable failed
 593
 594 .IP "41"
 595 Kernel channel enable failed
 596
 597 .IP "42"
 598 Kernel context failed
 599
 600 .IP "43"
 601 Kernel enable event failed
 602
 603 .IP "44"
 604 Kernel disable event failed
 605
 606 .IP "53"
 607 Kernel listing events failed
 608
 609 .IP "60"
 610 UST channel disable failed
 611
 612 .IP "61"
 613 UST channel enable failed
 614
 615 .IP "62"
 616 UST adding context failed
 617
 618 .IP "63"
 619 UST event enable failed
 620
 621 .IP "64"
 622 UST event disable failed
 623
 624 .IP "66"
 625 UST start failed
 626
 627 .IP "67"
 628 UST stop failed
 629
 630 .IP "75"
 631 UST event exists
 632
 633 .IP "76"
 634 UST event not found
 635
 636 .IP "77"
 637 UST context exists
 638
 639 .IP "78"
 640 UST invalid context
 641
 642 .IP "79"
 643 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
 644 user membership.
 645
 646 .IP "80"
 647 Tracing already started
 648
 649 .IP "81"
 650 Tracing already stopped
 651
 652 .IP "98"
 653 No UST consumer detected
 654
 655 .IP "99"
 656 No Kernel consumer detected
 657
 658 .IP "100"
 659 Event already enabled with different loglevel
 660 .PP
 661 .SH "ENVIRONMENT VARIABLES"
 662
 663 .PP
 664 Note that all command line options override environment variables.
 665 .PP
 666
 667 .PP
 668 .IP "LTTNG_SESSIOND_PATH"
 669 Allows one to specify the full session daemon binary path to lttng command line
 670 tool. You can also use \-\-sessiond-path option having the same effect.
 671 .SH "SEE ALSO"
 672
 673 .PP
 674 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
 675 .PP
 676 .SH "BUGS"
 677
 678 .PP
 679 No show stopper bugs are known yet in this version.
 680
 681 If you encounter any issues or usability problem, please report it on our
 682 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
 683 .SH "CREDITS"
 684
 685 .PP
 686 lttng is distributed under the GNU General Public License version 2. See the file
 687 COPYING for details.
 688 .PP
 689 A Web site is available at http://lttng.org for more information on the LTTng
 690 project.
 691 .PP
 692 You can also find our git tree at http://git.lttng.org.
 693 .PP
 694 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
 695 .PP
 696 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
 697 .PP
 698 .SH "THANKS"
 699
 700 .PP
 701 Thanks to Yannick Brosseau without whom this project would never have been so
 702 lean and mean! Also thanks to the Ericsson teams working on tracing which
 703 helped us greatly with detailed bug reports and unusual test cases.
 704
 705 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
 706 maintainer) and Jon Bernard for our Debian packages.
 707
 708 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
 709 Montreal for the LTTng journey.
 710 .PP
 711 .SH "AUTHORS"
 712
 713 .PP
 714 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
 715 David Goulet. More people have since contributed to it. It is currently
 716 maintained by David Goulet <dgoulet@efficios.com>.
 717 .PP