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 .fi
 344
 345 .IP "\fBdisable-channel\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
 346 .nf
 347 Disable tracing channel
 348
 349 Disabling a channel makes all event(s) in that channel to stop tracing. You can
 350 enable it back by calling \fBlttng enable-channel NAME\fP again.
 351
 352 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 353 file.
 354 .fi
 355
 356 .B OPTIONS:
 357
 358 .nf
 359 \-h, \-\-help
 360         Show summary of possible options and commands.
 361 \-\-list-options
 362         Simple listing of options
 363 \-s, \-\-session
 364         Apply on session name
 365 \-k, \-\-kernel
 366         Apply for the kernel tracer
 367 \-u, \-\-userspace
 368         Apply for the user-space tracer
 369 .fi
 370
 371 .IP "\fBdisable-event\fP NAME[,NAME2,...] [\-k|\-u] [OPTIONS]"
 372 .nf
 373 Disable tracing event
 374
 375 The event, once disabled, can be re-enabled by calling \fBlttng enable-event
 376 NAME\fP again.
 377
 378 If \fB\-s, \-\-session\fP is omitted, the session name is taken from the .lttngrc
 379 file.
 380 .fi
 381
 382 .B OPTIONS:
 383
 384 .nf
 385 \-h, \-\-help
 386         Show summary of possible options and commands.
 387 \-\-list-options
 388         Simple listing of options
 389 \-s, \-\-session
 390         Apply on session name
 391 \-k, \-\-kernel
 392         Apply for the kernel tracer
 393 \-u, \-\-userspace
 394         Apply for the user-space tracer
 395 .fi
 396
 397 .IP "\fBlist\fP [\-k|\-u] [SESSION [SESSION_OPTIONS]]"
 398 .nf
 399 List tracing session information.
 400
 401 With no arguments, it will list available tracing session(s).
 402
 403 With the session name, it will display the details of the session including
 404 the trace file path, the associated channels and their state (activated
 405 and deactivated), the activated events and more.
 406
 407 With \-k alone, it will list all available kernel events (except the system
 408 calls events).
 409 With \-u alone, it will list all available user-space events from registered
 410 applications. Here is an example of 'lttng list \-u':
 411
 412 PID: 7448 - Name: /tmp/lttng-ust/tests/hello/.libs/lt-hello
 413       ust_tests_hello:tptest_sighandler (type: tracepoint)
 414       ust_tests_hello:tptest (type: tracepoint)
 415
 416 You can now enable any event listed by using the name :
 417 \fBust_tests_hello:tptest\fP.
 418 .fi
 419
 420 .B OPTIONS:
 421
 422 .nf
 423 \-h, \-\-help
 424         Show summary of possible options and commands.
 425 \-\-list-options
 426         Simple listing of options
 427 \-k, \-\-kernel
 428         Select kernel domain
 429 \-u, \-\-userspace
 430         Select user-space domain.
 431
 432 Session options:
 433 \-c, \-\-channel NAME
 434         List details of a channel
 435 \-d, \-\-domain
 436         List available domain(s)
 437 .fi
 438
 439 .IP "\fBset-session\fP NAME"
 440 .nf
 441 Set current session name
 442
 443 Will change the session name in the .lttngrc file.
 444 .fi
 445
 446 .B OPTIONS:
 447
 448 .nf
 449 \-h, \-\-help
 450         Show summary of possible options and commands.
 451 \-\-list-options
 452         Simple listing of options
 453 .fi
 454
 455 .IP
 456
 457 .IP "\fBstart\fP [OPTIONS] [NAME]"
 458 .nf
 459 Start tracing
 460
 461 It will start tracing for all tracers for a specific tracing session.
 462
 463 If NAME is omitted, the session name is taken from the .lttngrc file.
 464 .fi
 465
 466 .B OPTIONS:
 467
 468 .nf
 469 \-h, \-\-help
 470         Show summary of possible options and commands.
 471 \-\-list-options
 472         Simple listing of options
 473 .fi
 474
 475 .IP
 476
 477 .IP "\fBstop\fP [OPTIONS] [NAME]"
 478 .nf
 479 Stop tracing
 480
 481 It will stop tracing for all tracers for a specific tracing session.
 482
 483 If NAME is omitted, the session name is taken from the .lttngrc file.
 484 .fi
 485
 486 .B OPTIONS:
 487
 488 .nf
 489 \-h, \-\-help
 490         Show summary of possible options and commands.
 491 \-\-list-options
 492         Simple listing of options
 493 .fi
 494
 495 .IP
 496
 497 .IP "\fBversion\fP"
 498 .nf
 499 Show version information
 500 .fi
 501
 502 .B OPTIONS:
 503
 504 .nf
 505 \-h, \-\-help
 506         Show summary of possible options and commands.
 507 \-\-list-options
 508         Simple listing of options
 509 .fi
 510
 511 .IP
 512
 513 .IP "\fBview\fP [SESSION_NAME] [OPTIONS]"
 514 .nf
 515 View traces of a tracing session
 516
 517 By default, the babeltrace viewer will be used for text viewing.
 518
 519 If SESSION_NAME is omitted, the session name is taken from the .lttngrc file.
 520
 521 .fi
 522
 523 .B OPTIONS:
 524
 525 .nf
 526 \-h, \-\-help
 527         Show this help
 528 \-\-list-options
 529         Simple listing of options
 530 \-t, \-\-trace-path PATH
 531         Trace directory path for the viewer
 532 \-e, \-\-viewer CMD
 533         Specify viewer and/or options to use
 534         This will completely override the default viewers so
 535         please make sure to specify the full command. The trace
 536         directory path of the session will be appended at the end
 537         to the arguments
 538 .fi
 539
 540 .SH "EXIT VALUES"
 541
 542 .IP "0"
 543 Success
 544
 545 .IP "1"
 546 Command error
 547
 548 .IP "2"
 549 Undefined command
 550
 551 .IP "3"
 552 Fatal error
 553
 554 .IP "4"
 555 Command warning
 556
 557 .IP "16"
 558 No session found by the name given
 559
 560 .IP "18"
 561 Error in session creation
 562
 563 .IP "21"
 564 Error in application(s) listing
 565
 566 .IP "28"
 567 Session name already exists
 568
 569 .IP "33"
 570 Kernel tracer unavailable
 571
 572 .IP "35"
 573 Kernel event exists
 574
 575 .IP "37"
 576 Kernel channel exists
 577
 578 .IP "38"
 579 Kernel channel creation failed
 580
 581 .IP "39"
 582 Kernel channel not found
 583
 584 .IP "40"
 585 Kernel channel disable failed
 586
 587 .IP "41"
 588 Kernel channel enable failed
 589
 590 .IP "42"
 591 Kernel context failed
 592
 593 .IP "43"
 594 Kernel enable event failed
 595
 596 .IP "44"
 597 Kernel disable event failed
 598
 599 .IP "53"
 600 Kernel listing events failed
 601
 602 .IP "60"
 603 UST channel disable failed
 604
 605 .IP "61"
 606 UST channel enable failed
 607
 608 .IP "62"
 609 UST adding context failed
 610
 611 .IP "63"
 612 UST event enable failed
 613
 614 .IP "64"
 615 UST event disable failed
 616
 617 .IP "66"
 618 UST start failed
 619
 620 .IP "67"
 621 UST stop failed
 622
 623 .IP "75"
 624 UST event exists
 625
 626 .IP "76"
 627 UST event not found
 628
 629 .IP "77"
 630 UST context exists
 631
 632 .IP "78"
 633 UST invalid context
 634
 635 .IP "79"
 636 Tracing the kernel requires a root lttng-sessiond daemon and "tracing" group
 637 user membership.
 638
 639 .IP "80"
 640 Tracing already started
 641
 642 .IP "81"
 643 Tracing already stopped
 644
 645 .IP "98"
 646 No UST consumer detected
 647
 648 .IP "99"
 649 No Kernel consumer detected
 650
 651 .IP "100"
 652 Event already enabled with different loglevel
 653 .PP
 654 .SH "ENVIRONMENT VARIABLES"
 655
 656 .PP
 657 Note that all command line options override environment variables.
 658 .PP
 659
 660 .PP
 661 .IP "LTTNG_SESSIOND_PATH"
 662 Allows one to specify the full session daemon binary path to lttng command line
 663 tool. You can also use \-\-sessiond-path option having the same effect.
 664 .SH "SEE ALSO"
 665
 666 .PP
 667 babeltrace(1), lttng-ust(3), lttng-sessiond(8)
 668 .PP
 669 .SH "BUGS"
 670
 671 .PP
 672 No show stopper bugs are known yet in this version.
 673
 674 If you encounter any issues or usability problem, please report it on our
 675 mailing list <lttng-dev@lists.lttng.org> to help improve this project.
 676 .SH "CREDITS"
 677
 678 .PP
 679 lttng is distributed under the GNU General Public License version 2. See the file
 680 COPYING for details.
 681 .PP
 682 A Web site is available at http://lttng.org for more information on the LTTng
 683 project.
 684 .PP
 685 You can also find our git tree at http://git.lttng.org.
 686 .PP
 687 Mailing lists for support and development: <lttng-dev@lists.lttng.org>.
 688 .PP
 689 You can find us on IRC server irc.oftc.net (OFTC) in #lttng.
 690 .PP
 691 .SH "THANKS"
 692
 693 .PP
 694 Thanks to Yannick Brosseau without whom this project would never have been so
 695 lean and mean! Also thanks to the Ericsson teams working on tracing which
 696 helped us greatly with detailed bug reports and unusual test cases.
 697
 698 Thanks to our beloved packager Alexandre Montplaisir-Goncalves (Ubuntu and PPA
 699 maintainer) and Jon Bernard for our Debian packages.
 700
 701 Special thanks to Michel Dagenais and the DORSAL laboratory at Polytechnique de
 702 Montreal for the LTTng journey.
 703 .PP
 704 .SH "AUTHORS"
 705
 706 .PP
 707 lttng-tools was originally written by Mathieu Desnoyers, Julien Desfossez and
 708 David Goulet. More people have since contributed to it. It is currently
 709 maintained by David Goulet <dgoulet@efficios.com>.
 710 .PP