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 \-\-list-options
 243         Simple listing of options
 244 .fi
 245
 246 .IP
 247
 248 .IP "\fBenable-channel\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
 249 .nf
 250 Enable tracing channel
 251
 252 To enable event, you must first enable a channel which contains event(s).
 253
 254 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 255 file.
 256 .fi
 257
 258 .B OPTIONS:
 259
 260 .nf
 261 \-h, \-\-help
 262         Show this help
 263 \-\-list-options
 264         Simple listing of options
 265 \-s, \-\-session
 266         Apply on session name
 267 \-k, \-\-kernel
 268         Apply to the kernel tracer
 269 \-u, \-\-userspace
 270         Apply to the user-space tracer
 271
 272 \-\-discard
 273         Discard event when subbuffers are full (default)
 274 \-\-overwrite
 275         Flight recorder mode : overwrites events when subbuffers are full
 276 \-\-subbuf-size
 277         Subbuffer size in bytes (default: 4096, kernel default: 262144)
 278 \-\-num-subbuf
 279         Number of subbuffers (default: 4)
 280         Needs to be a power of 2 for kernel and ust tracers
 281 \-\-switch-timer
 282         Switch subbuffer timer interval in usec (default: 0)
 283         Needs to be a power of 2 for kernel and ust tracers
 284 \-\-read-timer
 285         Read timer interval in usec (default: 200)
 286 .fi
 287
 288 .IP
 289
 290 .IP "\fBenable-event\fP NAME[,NAME2,...] [-k|-u] [OPTIONS]"
 291 .nf
 292 Enable tracing event
 293
 294 A tracing event is always assigned to a channel. If \fB\-c, \-\-channel\fP is
 295 omitted, a default channel named '\fBchannel0\fP' is created and the event is
 296 added to it. For the user-space tracer, using \fB\-a, \-\-all\fP is the same as
 297 using the wildcard "*".
 298
 299 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 300 file.
 301 .fi
 302
 303 .B OPTIONS:
 304
 305 .nf
 306 \-h, \-\-help
 307         Show summary of possible options and commands.
 308 \-\-list-options
 309         Simple listing of options
 310 \-s, \-\-session
 311         Apply on session name
 312 \-c, \-\-channel
 313         Apply on channel name
 314 \-a, \-\-all
 315         Enable all tracepoints and syscalls
 316 \-k, \-\-kernel
 317         Apply for the kernel tracer
 318 \-u, \-\-userspace
 319         Apply for the user-space tracer
 320
 321 \-\-tracepoint
 322         Tracepoint event (default)
 323         - userspace tracer supports wildcards at end of string. Don't forget to
 324         quote to deal with bash expansion.
 325         e.g.:
 326         "*"
 327         "app_component:na*"
 328 \-\-loglevel
 329         Tracepoint loglevel
 330 \-\-probe [addr | symbol | symbol+offset]
 331         Dynamic probe. Addr and offset can be octal (0NNN...), decimal (NNN...)
 332         or hexadecimal (0xNNN...)
 333 \-\-function [addr | symbol | symbol+offset]
 334         Dynamic function entry/return probe. Addr and offset can be octal
 335         (0NNN...), decimal (NNN...) or hexadecimal (0xNNN...)
 336 \-\-syscall
 337         System call event
 338         Enabling syscalls tracing (kernel tracer), you will not be able to disable them
 339         with disable-event. This is a known limitation. You can disable the entire
 340         channel to do the trick.
 341 .fi
 342
 343 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
 344 .nf
 345 Disable tracing channel
 346
 347 Disabling a channel makes all event(s) in that channel to stop tracing. You can
 348 enable it back by calling \fBlttng enable-channel NAME\fP again.
 349
 350 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 351 file.
 352 .fi
 353
 354 .B OPTIONS:
 355
 356 .nf
 357 \-h, \-\-help
 358         Show summary of possible options and commands.
 359 \-\-list-options
 360         Simple listing of options
 361 \-s, \-\-session
 362         Apply on session name
 363 \-k, \-\-kernel
 364         Apply for the kernel tracer
 365 \-u, \-\-userspace
 366         Apply for the user-space tracer
 367 .fi
 368
 369 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
 370 .nf
 371 Disable tracing event
 372
 373 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
 374 NAME\fP again.
 375
 376 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 377 file.
 378 .fi
 379
 380 .B OPTIONS:
 381
 382 .nf
 383 \-h, \-\-help
 384         Show summary of possible options and commands.
 385 \-\-list-options
 386         Simple listing of options
 387 \-s, \-\-session
 388         Apply on session name
 389 \-k, \-\-kernel
 390         Apply for the kernel tracer
 391 \-u, \-\-userspace
 392         Apply for the user-space tracer
 393 .fi
 394
 395 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
 396 .nf
 397 List tracing session information.
 398
 399 With no arguments, it will list available tracing session(s).
 400
 401 With the session name, it will display the details of the session including
 402 the trace file path, the associated channels and their state (activated
 403 and deactivated), the activated events and more.
 404
 405 With \-k alone, it will list all available kernel events (except the system
 406 calls events).
 407 With \-u alone, it will list all available user-space events from registered
 408 applications. Here is an example of 'lttng list \-u':
 409
 410 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
 411       ust_tests_hello:tptest_sighandler (type: tracepoint)
 412       ust_tests_hello:tptest (type: tracepoint)
 413
 414 You can now enable any event listed by using the name :
 415 \fBust_tests_hello:tptest\fP.
 416 .fi
 417
 418 .B OPTIONS:
 419
 420 .nf
 421 \-h, \-\-help
 422         Show summary of possible options and commands.
 423 \-\-list-options
 424         Simple listing of options
 425 \-k, \-\-kernel
 426         Select kernel domain
 427 \-u, \-\-userspace
 428         Select user-space domain.
 429
 430 Session options:
 431 \-c, \-\-channel NAME
 432         List details of a channel
 433 \-d, \-\-domain
 434         List available domain(s)
 435 .fi
 436
 437 .IP "\fBset-session\fP NAME"
 438 .nf
 439 Set current session name
 440
 441 Will change the session name in the .lttngrc file.
 442 .fi
 443
 444 .B OPTIONS:
 445
 446 .nf
 447 \-h, \-\-help
 448         Show summary of possible options and commands.
 449 \-\-list-options
 450         Simple listing of options
 451 .fi
 452
 453 .IP
 454
 455 .IP "\fBstart\fP [OPTIONS] [NAME]"
 456 .nf
 457 Start tracing
 458
 459 It will start tracing for all tracers for a specific tracing session.
 460
 461 If NAME is omitted, the session name is taken from the .lttngrc file.
 462 .fi
 463
 464 .B OPTIONS:
 465
 466 .nf
 467 \-h, \-\-help
 468         Show summary of possible options and commands.
 469 \-\-list-options
 470         Simple listing of options
 471 .fi
 472
 473 .IP
 474
 475 .IP "\fBstop\fP [OPTIONS] [NAME]"
 476 .nf
 477 Stop tracing
 478
 479 It will stop tracing for all tracers for a specific tracing session.
 480
 481 If NAME is omitted, the session name is taken from the .lttngrc file.
 482 .fi
 483
 484 .B OPTIONS:
 485
 486 .nf
 487 \-h, \-\-help
 488         Show summary of possible options and commands.
 489 \-\-list-options
 490         Simple listing of options
 491 .fi
 492
 493 .IP
 494
 495 .IP "\fBversion\fP"
 496 .nf
 497 Show version information
 498 .fi
 499
 500 .B OPTIONS:
 501
 502 .nf
 503 \-h, \-\-help
 504         Show summary of possible options and commands.
 505 \-\-list-options
 506         Simple listing of options
 507 .fi
 508
 509 .IP
 510
 511 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
 512 .nf
 513 View traces of a tracing session
 514
 515 By default, the babeltrace viewer will be used for text viewing.
 516
 517 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
 518
 519 .fi
 520
 521 .B OPTIONS:
 522
 523 .nf
 524 \-h, \-\-help
 525         Show this help
 526 \-\-list-options
 527         Simple listing of options
 528 \-t, \-\-trace-path PATH
 529         Trace directory path for the viewer
 530 \-e, \-\-viewer CMD
 531         Specify viewer and/or options to use
 532         This will completely override the default viewers so
 533         please make sure to specify the full command. The trace
 534         directory path of the session will be appended at the end
 535         to the arguments
 536 .fi
 537
 538 .SH "EXIT VALUES"
 539
 540 .IP "0"
 541 Success
 542
 543 .IP "1"
 544 Command error
 545
 546 .IP "2"
 547 Undefined command
 548
 549 .IP "3"
 550 Fatal error
 551
 552 .IP "4"
 553 Command warning
 554
 555 .IP "16"
 556 No session found by the name given
 557
 558 .IP "18"
 559 Error in session creation
 560
 561 .IP "21"
 562 Error in application(s) listing
 563
 564 .IP "28"
 565 Session name already exists
 566
 567 .IP "33"
 568 Kernel tracer unavailable
 569
 570 .IP "35"
 571 Kernel event exists
 572
 573 .IP "37"
 574 Kernel channel exists
 575
 576 .IP "38"
 577 Kernel channel creation failed
 578
 579 .IP "39"
 580 Kernel channel not found
 581
 582 .IP "40"
 583 Kernel channel disable failed
 584
 585 .IP "41"
 586 Kernel channel enable failed
 587
 588 .IP "42"
 589 Kernel context failed
 590
 591 .IP "43"
 592 Kernel enable event failed
 593
 594 .IP "44"
 595 Kernel disable event failed
 596
 597 .IP "53"
 598 Kernel listing events failed
 599
 600 .IP "60"
 601 UST channel disable failed
 602
 603 .IP "61"
 604 UST channel enable failed
 605
 606 .IP "62"
 607 UST adding context failed
 608
 609 .IP "63"
 610 UST event enable failed
 611
 612 .IP "64"
 613 UST event disable failed
 614
 615 .IP "66"
 616 UST start failed
 617
 618 .IP "67"
 619 UST stop failed
 620
 621 .IP "75"
 622 UST event exists
 623
 624 .IP "76"
 625 UST event not found
 626
 627 .IP "77"
 628 UST context exists
 629
 630 .IP "78"
 631 UST invalid context
 632
 633 .IP "79"
 634 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
 635 user membership.
 636
 637 .IP "80"
 638 Tracing already started
 639
 640 .IP "81"
 641 Tracing already stopped
 642 .PP
 643 .SH "ENVIRONMENT VARIABLES"
 644
 645 .PP
 646 Note that all command line options override environment variables.
 647 .PP
 648
 649 .PP
 650 .IP "LTTNG_SESSIOND_PATH"
 651 Allows one to specify the full session daemon binary path to lttng command line
 652 tool. You can also use \-\-sessiond-path option having the same effect.
 653 .SH "SEE ALSO"
 654
 655 .PP
 656 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
 657 .PP
 658 .SH "BUGS"
 659
 660 .PP
 661 No show stopper bugs are known yet in this version.
 662
 663 If you encounter any issues or usability problem, please report it on our
 664 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
 665 .SH "CREDITS"
 666
 667 .PP
 668 lttng is distributed under the GNU General Public License version 2. See the file
 669 COPYING for details.
 670 .PP
 671 A Web site is available at http://lttng.org for more information on the LTTng
 672 project.
 673 .PP
 674 You can also find our git tree at http://git.lttng.org.
 675 .PP
 676 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
 677 .PP
 678 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
 679 .PP
 680 .SH "THANKS"
 681
 682 .PP
 683 Thanks to Yannick Brosseau without whom this project would never have been so
 684 lean and mean! Also thanks to the Ericsson teams working on tracing which
 685 helped us greatly with detailed bug reports and unusual test cases.
 686
 687 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
 688 maintainer) and Jon Bernard for our Debian packages.
 689
 690 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
 691 Montreal for the LTTng journey.
 692 .PP
 693 .SH "AUTHORS"
 694
 695 .PP
 696 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
 697 David Goulet. More people have since contributed to it. It is currently
 698 maintained by David Goulet <dgoulet@efficios.com>.
 699 .PP