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e544221d JH |
1 | = Trace2 API |
2 | ||
3 | The Trace2 API can be used to print debug, performance, and telemetry | |
4 | information to stderr or a file. The Trace2 feature is inactive unless | |
5 | explicitly enabled by enabling one or more Trace2 Targets. | |
6 | ||
7 | The Trace2 API is intended to replace the existing (Trace1) | |
c191b918 | 8 | `printf()`-style tracing provided by the existing `GIT_TRACE` and |
e544221d JH |
9 | `GIT_TRACE_PERFORMANCE` facilities. During initial implementation, |
10 | Trace2 and Trace1 may operate in parallel. | |
11 | ||
12 | The Trace2 API defines a set of high-level messages with known fields, | |
13 | such as (`start`: `argv`) and (`exit`: {`exit-code`, `elapsed-time`}). | |
14 | ||
15 | Trace2 instrumentation throughout the Git code base sends Trace2 | |
16 | messages to the enabled Trace2 Targets. Targets transform these | |
17 | messages content into purpose-specific formats and write events to | |
18 | their data streams. In this manner, the Trace2 API can drive | |
19 | many different types of analysis. | |
20 | ||
21 | Targets are defined using a VTable allowing easy extension to other | |
22 | formats in the future. This might be used to define a binary format, | |
23 | for example. | |
24 | ||
81567caf | 25 | Trace2 is controlled using `trace2.*` config values in the system and |
e4b75d6a | 26 | global config files and `GIT_TRACE2*` environment variables. Trace2 does |
3188d3c0 JS |
27 | not read from repo local or worktree config files, nor does it respect |
28 | `-c` command line config settings. | |
81567caf | 29 | |
e544221d JH |
30 | == Trace2 Targets |
31 | ||
32 | Trace2 defines the following set of Trace2 Targets. | |
33 | Format details are given in a later section. | |
34 | ||
81567caf JH |
35 | === The Normal Format Target |
36 | ||
c191b918 | 37 | The normal format target is a traditional `printf()` format and similar |
1c538b95 | 38 | to the `GIT_TRACE` format. This format is enabled with the `GIT_TRACE2` |
81567caf JH |
39 | environment variable or the `trace2.normalTarget` system or global |
40 | config setting. | |
41 | ||
42 | For example | |
e544221d | 43 | |
e544221d | 44 | ------------ |
e4b75d6a | 45 | $ export GIT_TRACE2=~/log.normal |
e544221d JH |
46 | $ git version |
47 | git version 2.20.1.155.g426c96fcdb | |
48 | ------------ | |
81567caf JH |
49 | |
50 | or | |
51 | ||
52 | ------------ | |
53 | $ git config --global trace2.normalTarget ~/log.normal | |
54 | $ git version | |
55 | git version 2.20.1.155.g426c96fcdb | |
56 | ------------ | |
57 | ||
58 | yields | |
59 | ||
e544221d JH |
60 | ------------ |
61 | $ cat ~/log.normal | |
62 | 12:28:42.620009 common-main.c:38 version 2.20.1.155.g426c96fcdb | |
63 | 12:28:42.620989 common-main.c:39 start git version | |
64 | 12:28:42.621101 git.c:432 cmd_name version (version) | |
65 | 12:28:42.621215 git.c:662 exit elapsed:0.001227 code:0 | |
66 | 12:28:42.621250 trace2/tr2_tgt_normal.c:124 atexit elapsed:0.001265 code:0 | |
67 | ------------ | |
68 | ||
81567caf JH |
69 | === The Performance Format Target |
70 | ||
71 | The performance format target (PERF) is a column-based format to | |
1c538b95 JS |
72 | replace `GIT_TRACE_PERFORMANCE` and is suitable for development and |
73 | testing, possibly to complement tools like `gprof`. This format is | |
e4b75d6a | 74 | enabled with the `GIT_TRACE2_PERF` environment variable or the |
81567caf JH |
75 | `trace2.perfTarget` system or global config setting. |
76 | ||
77 | For example | |
e544221d | 78 | |
e544221d | 79 | ------------ |
e4b75d6a | 80 | $ export GIT_TRACE2_PERF=~/log.perf |
e544221d JH |
81 | $ git version |
82 | git version 2.20.1.155.g426c96fcdb | |
83 | ------------ | |
81567caf JH |
84 | |
85 | or | |
86 | ||
87 | ------------ | |
88 | $ git config --global trace2.perfTarget ~/log.perf | |
89 | $ git version | |
90 | git version 2.20.1.155.g426c96fcdb | |
91 | ------------ | |
92 | ||
93 | yields | |
94 | ||
e544221d JH |
95 | ------------ |
96 | $ cat ~/log.perf | |
97 | 12:28:42.620675 common-main.c:38 | d0 | main | version | | | | | 2.20.1.155.g426c96fcdb | |
39f43177 | 98 | 12:28:42.621001 common-main.c:39 | d0 | main | start | | 0.001173 | | | git version |
e544221d JH |
99 | 12:28:42.621111 git.c:432 | d0 | main | cmd_name | | | | | version (version) |
100 | 12:28:42.621225 git.c:662 | d0 | main | exit | | 0.001227 | | | code:0 | |
101 | 12:28:42.621259 trace2/tr2_tgt_perf.c:211 | d0 | main | atexit | | 0.001265 | | | code:0 | |
102 | ------------ | |
103 | ||
81567caf JH |
104 | === The Event Format Target |
105 | ||
106 | The event format target is a JSON-based format of event data suitable | |
e4b75d6a | 107 | for telemetry analysis. This format is enabled with the `GIT_TRACE2_EVENT` |
81567caf JH |
108 | environment variable or the `trace2.eventTarget` system or global config |
109 | setting. | |
110 | ||
111 | For example | |
e544221d | 112 | |
e544221d | 113 | ------------ |
e4b75d6a | 114 | $ export GIT_TRACE2_EVENT=~/log.event |
e544221d JH |
115 | $ git version |
116 | git version 2.20.1.155.g426c96fcdb | |
117 | ------------ | |
e544221d | 118 | |
81567caf | 119 | or |
e544221d | 120 | |
81567caf JH |
121 | ------------ |
122 | $ git config --global trace2.eventTarget ~/log.event | |
123 | $ git version | |
124 | git version 2.20.1.155.g426c96fcdb | |
125 | ------------ | |
e544221d | 126 | |
81567caf | 127 | yields |
e544221d | 128 | |
81567caf JH |
129 | ------------ |
130 | $ cat ~/log.event | |
c4667b17 | 131 | {"event":"version","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"3","exe":"2.20.1.155.g426c96fcdb"} |
81567caf JH |
132 | {"event":"start","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621027Z","file":"common-main.c","line":39,"t_abs":0.001173,"argv":["git","version"]} |
133 | {"event":"cmd_name","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621122Z","file":"git.c","line":432,"name":"version","hierarchy":"version"} | |
134 | {"event":"exit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621236Z","file":"git.c","line":662,"t_abs":0.001227,"code":0} | |
135 | {"event":"atexit","sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.621268Z","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0} | |
136 | ------------ | |
e544221d | 137 | |
81567caf | 138 | === Enabling a Target |
e544221d | 139 | |
81567caf JH |
140 | To enable a target, set the corresponding environment variable or |
141 | system or global config value to one of the following: | |
a4d3a283 | 142 | |
81567caf | 143 | include::../trace2-target-values.txt[] |
e544221d | 144 | |
3d4548e7 JS |
145 | When trace files are written to a target directory, they will be named according |
146 | to the last component of the SID (optionally followed by a counter to avoid | |
147 | filename collisions). | |
e544221d JH |
148 | |
149 | == Trace2 API | |
150 | ||
151 | All public Trace2 functions and macros are defined in `trace2.h` and | |
152 | `trace2.c`. All public symbols are prefixed with `trace2_`. | |
153 | ||
154 | There are no public Trace2 data structures. | |
155 | ||
156 | The Trace2 code also defines a set of private functions and data types | |
157 | in the `trace2/` directory. These symbols are prefixed with `tr2_` | |
158 | and should only be used by functions in `trace2.c`. | |
159 | ||
160 | == Conventions for Public Functions and Macros | |
161 | ||
162 | The functions defined by the Trace2 API are declared and documented | |
163 | in `trace2.h`. It defines the API functions and wrapper macros for | |
164 | Trace2. | |
165 | ||
166 | Some functions have a `_fl()` suffix to indicate that they take `file` | |
167 | and `line-number` arguments. | |
168 | ||
169 | Some functions have a `_va_fl()` suffix to indicate that they also | |
170 | take a `va_list` argument. | |
171 | ||
172 | Some functions have a `_printf_fl()` suffix to indicate that they also | |
236d1177 | 173 | take a `printf()` style format with a variable number of arguments. |
e544221d | 174 | |
1c538b95 | 175 | There are CPP wrapper macros and `#ifdef`s to hide most of these details. |
e544221d JH |
176 | See `trace2.h` for more details. The following discussion will only |
177 | describe the simplified forms. | |
178 | ||
179 | == Public API | |
180 | ||
031fd4b9 | 181 | All Trace2 API functions send a message to all of the active |
e544221d JH |
182 | Trace2 Targets. This section describes the set of available |
183 | messages. | |
184 | ||
185 | It helps to divide these functions into groups for discussion | |
186 | purposes. | |
187 | ||
188 | === Basic Command Messages | |
189 | ||
190 | These are concerned with the lifetime of the overall git process. | |
6c51cb52 HW |
191 | e.g: `void trace2_initialize_clock()`, `void trace2_initialize()`, |
192 | `int trace2_is_enabled()`, `void trace2_cmd_start(int argc, const char **argv)`. | |
e544221d JH |
193 | |
194 | === Command Detail Messages | |
195 | ||
196 | These are concerned with describing the specific Git command | |
197 | after the command line, config, and environment are inspected. | |
6c51cb52 HW |
198 | e.g: `void trace2_cmd_name(const char *name)`, |
199 | `void trace2_cmd_mode(const char *mode)`. | |
e544221d JH |
200 | |
201 | === Child Process Messages | |
202 | ||
203 | These are concerned with the various spawned child processes, | |
204 | including shell scripts, git commands, editors, pagers, and hooks. | |
205 | ||
6c51cb52 | 206 | e.g: `void trace2_child_start(struct child_process *cmd)`. |
e544221d JH |
207 | |
208 | === Git Thread Messages | |
209 | ||
210 | These messages are concerned with Git thread usage. | |
211 | ||
6c51cb52 | 212 | e.g: `void trace2_thread_start(const char *thread_name)`. |
e544221d JH |
213 | |
214 | === Region and Data Messages | |
215 | ||
216 | These are concerned with recording performance data | |
6c51cb52 HW |
217 | over regions or spans of code. e.g: |
218 | `void trace2_region_enter(const char *category, const char *label, const struct repository *repo)`. | |
e544221d | 219 | |
6c51cb52 | 220 | Refer to trace2.h for details about all trace2 functions. |
e544221d JH |
221 | |
222 | == Trace2 Target Formats | |
223 | ||
224 | === NORMAL Format | |
225 | ||
e544221d JH |
226 | Events are written as lines of the form: |
227 | ||
228 | ------------ | |
229 | [<time> SP <filename>:<line> SP+] <event-name> [[SP] <event-message>] LF | |
230 | ------------ | |
231 | ||
232 | `<event-name>`:: | |
233 | ||
234 | is the event name. | |
235 | ||
236 | `<event-message>`:: | |
c191b918 | 237 | is a free-form `printf()` message intended for human consumption. |
e544221d JH |
238 | + |
239 | Note that this may contain embedded LF or CRLF characters that are | |
240 | not escaped, so the event may spill across multiple lines. | |
241 | ||
e4b75d6a | 242 | If `GIT_TRACE2_BRIEF` or `trace2.normalBrief` is true, the `time`, `filename`, |
81567caf | 243 | and `line` fields are omitted. |
e544221d JH |
244 | |
245 | This target is intended to be more of a summary (like GIT_TRACE) and | |
246 | less detailed than the other targets. It ignores thread, region, and | |
247 | data messages, for example. | |
248 | ||
249 | === PERF Format | |
250 | ||
e544221d JH |
251 | Events are written as lines of the form: |
252 | ||
253 | ------------ | |
254 | [<time> SP <filename>:<line> SP+ | |
255 | BAR SP] d<depth> SP | |
256 | BAR SP <thread-name> SP+ | |
257 | BAR SP <event-name> SP+ | |
258 | BAR SP [r<repo-id>] SP+ | |
259 | BAR SP [<t_abs>] SP+ | |
260 | BAR SP [<t_rel>] SP+ | |
261 | BAR SP [<category>] SP+ | |
262 | BAR SP DOTS* <perf-event-message> | |
263 | LF | |
264 | ------------ | |
265 | ||
266 | `<depth>`:: | |
267 | is the git process depth. This is the number of parent | |
268 | git processes. A top-level git command has depth value "d0". | |
269 | A child of it has depth value "d1". A second level child | |
270 | has depth value "d2" and so on. | |
271 | ||
272 | `<thread-name>`:: | |
273 | is a unique name for the thread. The primary thread | |
274 | is called "main". Other thread names are of the form "th%d:%s" | |
275 | and include a unique number and the name of the thread-proc. | |
276 | ||
277 | `<event-name>`:: | |
278 | is the event name. | |
279 | ||
280 | `<repo-id>`:: | |
281 | when present, is a number indicating the repository | |
282 | in use. A `def_repo` event is emitted when a repository is | |
283 | opened. This defines the repo-id and associated worktree. | |
284 | Subsequent repo-specific events will reference this repo-id. | |
285 | + | |
286 | Currently, this is always "r1" for the main repository. | |
287 | This field is in anticipation of in-proc submodules in the future. | |
288 | ||
289 | `<t_abs>`:: | |
290 | when present, is the absolute time in seconds since the | |
291 | program started. | |
292 | ||
293 | `<t_rel>`:: | |
294 | when present, is time in seconds relative to the start of | |
295 | the current region. For a thread-exit event, it is the elapsed | |
296 | time of the thread. | |
297 | ||
298 | `<category>`:: | |
299 | is present on region and data events and is used to | |
300 | indicate a broad category, such as "index" or "status". | |
301 | ||
302 | `<perf-event-message>`:: | |
c191b918 | 303 | is a free-form `printf()` message intended for human consumption. |
e544221d JH |
304 | |
305 | ------------ | |
306 | 15:33:33.532712 wt-status.c:2310 | d0 | main | region_enter | r1 | 0.126064 | | status | label:print | |
307 | 15:33:33.532712 wt-status.c:2331 | d0 | main | region_leave | r1 | 0.127568 | 0.001504 | status | label:print | |
308 | ------------ | |
309 | ||
e4b75d6a | 310 | If `GIT_TRACE2_PERF_BRIEF` or `trace2.perfBrief` is true, the `time`, `file`, |
81567caf | 311 | and `line` fields are omitted. |
e544221d JH |
312 | |
313 | ------------ | |
314 | d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload | |
315 | ------------ | |
316 | ||
317 | The PERF target is intended for interactive performance analysis | |
318 | during development and is quite noisy. | |
319 | ||
320 | === EVENT Format | |
321 | ||
e544221d JH |
322 | Each event is a JSON-object containing multiple key/value pairs |
323 | written as a single line and followed by a LF. | |
324 | ||
325 | ------------ | |
326 | '{' <key> ':' <value> [',' <key> ':' <value>]* '}' LF | |
327 | ------------ | |
328 | ||
329 | Some key/value pairs are common to all events and some are | |
330 | event-specific. | |
331 | ||
332 | ==== Common Key/Value Pairs | |
333 | ||
334 | The following key/value pairs are common to all events: | |
335 | ||
336 | ------------ | |
337 | { | |
338 | "event":"version", | |
81567caf | 339 | "sid":"20190408T191827.272759Z-H9b68c35f-P00003510", |
e544221d | 340 | "thread":"main", |
08881b9a | 341 | "time":"2019-04-08T19:18:27.282761Z", |
e544221d | 342 | "file":"common-main.c", |
08881b9a | 343 | "line":42, |
e544221d JH |
344 | ... |
345 | } | |
346 | ------------ | |
347 | ||
348 | `"event":<event>`:: | |
349 | is the event name. | |
350 | ||
351 | `"sid":<sid>`:: | |
352 | is the session-id. This is a unique string to identify the | |
353 | process instance to allow all events emitted by a process to | |
354 | be identified. A session-id is used instead of a PID because | |
355 | PIDs are recycled by the OS. For child git processes, the | |
356 | session-id is prepended with the session-id of the parent git | |
357 | process to allow parent-child relationships to be identified | |
358 | during post-processing. | |
359 | ||
360 | `"thread":<thread>`:: | |
361 | is the thread name. | |
362 | ||
363 | `"time":<time>`:: | |
364 | is the UTC time of the event. | |
365 | ||
366 | `"file":<filename>`:: | |
367 | is source file generating the event. | |
368 | ||
369 | `"line":<line-number>`:: | |
370 | is the integer source line number generating the event. | |
371 | ||
372 | `"repo":<repo-id>`:: | |
373 | when present, is the integer repo-id as described previously. | |
374 | ||
e4b75d6a | 375 | If `GIT_TRACE2_EVENT_BRIEF` or `trace2.eventBrief` is true, the `file` |
81567caf JH |
376 | and `line` fields are omitted from all events and the `time` field is |
377 | only present on the "start" and "atexit" events. | |
e544221d JH |
378 | |
379 | ==== Event-Specific Key/Value Pairs | |
380 | ||
381 | `"version"`:: | |
22541013 JS |
382 | This event gives the version of the executable and the EVENT format. It |
383 | should always be the first event in a trace session. The EVENT format | |
384 | version will be incremented if new event types are added, if existing | |
385 | fields are removed, or if there are significant changes in | |
386 | interpretation of existing events or fields. Smaller changes, such as | |
387 | adding a new field to an existing event, will not require an increment | |
388 | to the EVENT format version. | |
e544221d JH |
389 | + |
390 | ------------ | |
391 | { | |
392 | "event":"version", | |
393 | ... | |
04480e67 | 394 | "evt":"3", # EVENT format version |
e544221d JH |
395 | "exe":"2.20.1.155.g426c96fcdb" # git version |
396 | } | |
397 | ------------ | |
398 | ||
7ba68e0c | 399 | `"too_many_files"`:: |
87db61a4 JS |
400 | This event is written to the git-trace2-discard sentinel file if there |
401 | are too many files in the target trace directory (see the | |
402 | trace2.maxFiles config option). | |
403 | + | |
404 | ------------ | |
405 | { | |
7ba68e0c | 406 | "event":"too_many_files", |
87db61a4 JS |
407 | ... |
408 | } | |
409 | ------------ | |
410 | ||
e544221d JH |
411 | `"start"`:: |
412 | This event contains the complete argv received by main(). | |
413 | + | |
414 | ------------ | |
415 | { | |
416 | "event":"start", | |
417 | ... | |
39f43177 | 418 | "t_abs":0.001227, # elapsed time in seconds |
e544221d JH |
419 | "argv":["git","version"] |
420 | } | |
421 | ------------ | |
422 | ||
423 | `"exit"`:: | |
424 | This event is emitted when git calls `exit()`. | |
425 | + | |
426 | ------------ | |
427 | { | |
428 | "event":"exit", | |
429 | ... | |
430 | "t_abs":0.001227, # elapsed time in seconds | |
431 | "code":0 # exit code | |
432 | } | |
433 | ------------ | |
434 | ||
435 | `"atexit"`:: | |
436 | This event is emitted by the Trace2 `atexit` routine during | |
437 | final shutdown. It should be the last event emitted by the | |
438 | process. | |
439 | + | |
440 | (The elapsed time reported here is greater than the time reported in | |
441 | the "exit" event because it runs after all other atexit tasks have | |
442 | completed.) | |
443 | + | |
444 | ------------ | |
445 | { | |
446 | "event":"atexit", | |
447 | ... | |
448 | "t_abs":0.001227, # elapsed time in seconds | |
449 | "code":0 # exit code | |
450 | } | |
451 | ------------ | |
452 | ||
453 | `"signal"`:: | |
454 | This event is emitted when the program is terminated by a user | |
455 | signal. Depending on the platform, the signal event may | |
456 | prevent the "atexit" event from being generated. | |
457 | + | |
458 | ------------ | |
459 | { | |
460 | "event":"signal", | |
461 | ... | |
462 | "t_abs":0.001227, # elapsed time in seconds | |
24df0d49 | 463 | "signo":13 # SIGTERM, SIGINT, etc. |
e544221d JH |
464 | } |
465 | ------------ | |
466 | ||
467 | `"error"`:: | |
0cc05b04 ÆAB |
468 | This event is emitted when one of the `BUG()`, `bug()`, `error()`, |
469 | `die()`, `warning()`, or `usage()` functions are called. | |
e544221d JH |
470 | + |
471 | ------------ | |
472 | { | |
473 | "event":"error", | |
474 | ... | |
475 | "msg":"invalid option: --cahced", # formatted error message | |
476 | "fmt":"invalid option: %s" # error format string | |
477 | } | |
478 | ------------ | |
479 | + | |
480 | The error event may be emitted more than once. The format string | |
481 | allows post-processors to group errors by type without worrying | |
482 | about specific error arguments. | |
483 | ||
484 | `"cmd_path"`:: | |
485 | This event contains the discovered full path of the git | |
486 | executable (on platforms that are configured to resolve it). | |
487 | + | |
488 | ------------ | |
489 | { | |
490 | "event":"cmd_path", | |
491 | ... | |
492 | "path":"C:/work/gfw/git.exe" | |
493 | } | |
494 | ------------ | |
495 | ||
2f732bf1 ES |
496 | `"cmd_ancestry"`:: |
497 | This event contains the text command name for the parent (and earlier | |
498 | generations of parents) of the current process, in an array ordered from | |
499 | nearest parent to furthest great-grandparent. It may not be implemented | |
500 | on all platforms. | |
501 | + | |
502 | ------------ | |
503 | { | |
504 | "event":"cmd_ancestry", | |
505 | ... | |
506 | "ancestry":["bash","tmux: server","systemd"] | |
507 | } | |
508 | ------------ | |
509 | ||
e544221d JH |
510 | `"cmd_name"`:: |
511 | This event contains the command name for this git process | |
512 | and the hierarchy of commands from parent git processes. | |
513 | + | |
514 | ------------ | |
515 | { | |
516 | "event":"cmd_name", | |
517 | ... | |
518 | "name":"pack-objects", | |
519 | "hierarchy":"push/pack-objects" | |
520 | } | |
521 | ------------ | |
522 | + | |
523 | Normally, the "name" field contains the canonical name of the | |
524 | command. When a canonical name is not available, one of | |
525 | these special values are used: | |
526 | + | |
527 | ------------ | |
528 | "_query_" # "git --html-path" | |
529 | "_run_dashed_" # when "git foo" tries to run "git-foo" | |
530 | "_run_shell_alias_" # alias expansion to a shell command | |
531 | "_run_git_alias_" # alias expansion to a git command | |
532 | "_usage_" # usage error | |
533 | ------------ | |
534 | ||
535 | `"cmd_mode"`:: | |
a6c80c31 | 536 | This event, when present, describes the command variant. This |
e544221d JH |
537 | event may be emitted more than once. |
538 | + | |
539 | ------------ | |
540 | { | |
541 | "event":"cmd_mode", | |
542 | ... | |
543 | "name":"branch" | |
544 | } | |
545 | ------------ | |
546 | + | |
547 | The "name" field is an arbitrary string to describe the command mode. | |
548 | For example, checkout can checkout a branch or an individual file. | |
549 | And these variations typically have different performance | |
550 | characteristics that are not comparable. | |
551 | ||
552 | `"alias"`:: | |
553 | This event is present when an alias is expanded. | |
554 | + | |
555 | ------------ | |
556 | { | |
557 | "event":"alias", | |
558 | ... | |
559 | "alias":"l", # registered alias | |
560 | "argv":["log","--graph"] # alias expansion | |
561 | } | |
562 | ------------ | |
563 | ||
564 | `"child_start"`:: | |
565 | This event describes a child process that is about to be | |
566 | spawned. | |
567 | + | |
568 | ------------ | |
569 | { | |
570 | "event":"child_start", | |
571 | ... | |
572 | "child_id":2, | |
573 | "child_class":"?", | |
574 | "use_shell":false, | |
575 | "argv":["git","rev-list","--objects","--stdin","--not","--all","--quiet"] | |
576 | ||
577 | "hook_name":"<hook_name>" # present when child_class is "hook" | |
578 | "cd":"<path>" # present when cd is required | |
579 | } | |
580 | ------------ | |
581 | + | |
582 | The "child_id" field can be used to match this child_start with the | |
583 | corresponding child_exit event. | |
584 | + | |
585 | The "child_class" field is a rough classification, such as "editor", | |
586 | "pager", "transport/*", and "hook". Unclassified children are classified | |
587 | with "?". | |
588 | ||
589 | `"child_exit"`:: | |
590 | This event is generated after the current process has returned | |
c191b918 | 591 | from the `waitpid()` and collected the exit information from the |
e544221d JH |
592 | child. |
593 | + | |
594 | ------------ | |
595 | { | |
596 | "event":"child_exit", | |
597 | ... | |
598 | "child_id":2, | |
599 | "pid":14708, # child PID | |
600 | "code":0, # child exit-code | |
601 | "t_rel":0.110605 # observed run-time of child process | |
602 | } | |
603 | ------------ | |
604 | + | |
605 | Note that the session-id of the child process is not available to | |
606 | the current/spawning process, so the child's PID is reported here as | |
607 | a hint for post-processing. (But it is only a hint because the child | |
031fd4b9 | 608 | process may be a shell script which doesn't have a session-id.) |
e544221d JH |
609 | + |
610 | Note that the `t_rel` field contains the observed run time in seconds | |
611 | for the child process (starting before the fork/exec/spawn and | |
c191b918 | 612 | stopping after the `waitpid()` and includes OS process creation overhead). |
e544221d JH |
613 | So this time will be slightly larger than the atexit time reported by |
614 | the child process itself. | |
615 | ||
64bc7524 JH |
616 | `"child_ready"`:: |
617 | This event is generated after the current process has started | |
618 | a background process and released all handles to it. | |
619 | + | |
620 | ------------ | |
621 | { | |
622 | "event":"child_ready", | |
623 | ... | |
624 | "child_id":2, | |
625 | "pid":14708, # child PID | |
626 | "ready":"ready", # child ready state | |
627 | "t_rel":0.110605 # observed run-time of child process | |
628 | } | |
629 | ------------ | |
630 | + | |
631 | Note that the session-id of the child process is not available to | |
632 | the current/spawning process, so the child's PID is reported here as | |
633 | a hint for post-processing. (But it is only a hint because the child | |
634 | process may be a shell script which doesn't have a session-id.) | |
635 | + | |
636 | This event is generated after the child is started in the background | |
637 | and given a little time to boot up and start working. If the child | |
3188d3c0 | 638 | starts up normally while the parent is still waiting, the "ready" |
64bc7524 JH |
639 | field will have the value "ready". |
640 | If the child is too slow to start and the parent times out, the field | |
641 | will have the value "timeout". | |
642 | If the child starts but the parent is unable to probe it, the field | |
643 | will have the value "error". | |
644 | + | |
645 | After the parent process emits this event, it will release all of its | |
646 | handles to the child process and treat the child as a background | |
647 | daemon. So even if the child does eventually finish booting up, | |
648 | the parent will not emit an updated event. | |
649 | + | |
650 | Note that the `t_rel` field contains the observed run time in seconds | |
651 | when the parent released the child process into the background. | |
652 | The child is assumed to be a long-running daemon process and may | |
653 | outlive the parent process. So the parent's child event times should | |
654 | not be compared to the child's atexit times. | |
655 | ||
e544221d JH |
656 | `"exec"`:: |
657 | This event is generated before git attempts to `exec()` | |
658 | another command rather than starting a child process. | |
659 | + | |
660 | ------------ | |
661 | { | |
662 | "event":"exec", | |
663 | ... | |
664 | "exec_id":0, | |
665 | "exe":"git", | |
666 | "argv":["foo", "bar"] | |
667 | } | |
668 | ------------ | |
669 | + | |
670 | The "exec_id" field is a command-unique id and is only useful if the | |
671 | `exec()` fails and a corresponding exec_result event is generated. | |
672 | ||
673 | `"exec_result"`:: | |
674 | This event is generated if the `exec()` fails and control | |
675 | returns to the current git command. | |
676 | + | |
677 | ------------ | |
678 | { | |
679 | "event":"exec_result", | |
680 | ... | |
681 | "exec_id":0, | |
682 | "code":1 # error code (errno) from exec() | |
683 | } | |
684 | ------------ | |
685 | ||
686 | `"thread_start"`:: | |
687 | This event is generated when a thread is started. It is | |
688 | generated from *within* the new thread's thread-proc (for TLS | |
689 | reasons). | |
690 | + | |
691 | ------------ | |
692 | { | |
693 | "event":"thread_start", | |
694 | ... | |
695 | "thread":"th02:preload_thread" # thread name | |
696 | } | |
697 | ------------ | |
698 | ||
699 | `"thread_exit"`:: | |
700 | This event is generated when a thread exits. It is generated | |
701 | from *within* the thread's thread-proc (for TLS reasons). | |
702 | + | |
703 | ------------ | |
704 | { | |
705 | "event":"thread_exit", | |
706 | ... | |
707 | "thread":"th02:preload_thread", # thread name | |
708 | "t_rel":0.007328 # thread elapsed time | |
709 | } | |
710 | ------------ | |
711 | ||
712 | `"def_param"`:: | |
3d3adaad JS |
713 | This event is generated to log a global parameter, such as a config |
714 | setting, command-line flag, or environment variable. | |
e544221d JH |
715 | + |
716 | ------------ | |
717 | { | |
718 | "event":"def_param", | |
719 | ... | |
35ae40ea | 720 | "scope":"global", |
e544221d JH |
721 | "param":"core.abbrev", |
722 | "value":"7" | |
723 | } | |
724 | ------------ | |
725 | ||
726 | `"def_repo"`:: | |
727 | This event defines a repo-id and associates it with the root | |
728 | of the worktree. | |
729 | + | |
730 | ------------ | |
731 | { | |
732 | "event":"def_repo", | |
733 | ... | |
734 | "repo":1, | |
735 | "worktree":"/Users/jeffhost/work/gfw" | |
736 | } | |
737 | ------------ | |
738 | + | |
739 | As stated earlier, the repo-id is currently always 1, so there will | |
740 | only be one def_repo event. Later, if in-proc submodules are | |
741 | supported, a def_repo event should be emitted for each submodule | |
742 | visited. | |
743 | ||
744 | `"region_enter"`:: | |
745 | This event is generated when entering a region. | |
746 | + | |
747 | ------------ | |
748 | { | |
749 | "event":"region_enter", | |
750 | ... | |
751 | "repo":1, # optional | |
752 | "nesting":1, # current region stack depth | |
753 | "category":"index", # optional | |
754 | "label":"do_read_index", # optional | |
755 | "msg":".git/index" # optional | |
756 | } | |
757 | ------------ | |
758 | + | |
759 | The `category` field may be used in a future enhancement to | |
760 | do category-based filtering. | |
761 | + | |
e4b75d6a | 762 | `GIT_TRACE2_EVENT_NESTING` or `trace2.eventNesting` can be used to |
e544221d JH |
763 | filter deeply nested regions and data events. It defaults to "2". |
764 | ||
765 | `"region_leave"`:: | |
766 | This event is generated when leaving a region. | |
767 | + | |
768 | ------------ | |
769 | { | |
770 | "event":"region_leave", | |
771 | ... | |
772 | "repo":1, # optional | |
773 | "t_rel":0.002876, # time spent in region in seconds | |
774 | "nesting":1, # region stack depth | |
775 | "category":"index", # optional | |
776 | "label":"do_read_index", # optional | |
777 | "msg":".git/index" # optional | |
778 | } | |
779 | ------------ | |
780 | ||
781 | `"data"`:: | |
782 | This event is generated to log a thread- and region-local | |
783 | key/value pair. | |
784 | + | |
785 | ------------ | |
786 | { | |
787 | "event":"data", | |
788 | ... | |
789 | "repo":1, # optional | |
790 | "t_abs":0.024107, # absolute elapsed time | |
791 | "t_rel":0.001031, # elapsed time in region/thread | |
792 | "nesting":2, # region stack depth | |
793 | "category":"index", | |
794 | "key":"read/cache_nr", | |
795 | "value":"3552" | |
796 | } | |
797 | ------------ | |
798 | + | |
799 | The "value" field may be an integer or a string. | |
800 | ||
801 | `"data-json"`:: | |
802 | This event is generated to log a pre-formatted JSON string | |
803 | containing structured data. | |
804 | + | |
805 | ------------ | |
806 | { | |
807 | "event":"data_json", | |
808 | ... | |
809 | "repo":1, # optional | |
810 | "t_abs":0.015905, | |
811 | "t_rel":0.015905, | |
812 | "nesting":1, | |
813 | "category":"process", | |
814 | "key":"windows/ancestry", | |
815 | "value":["bash.exe","bash.exe"] | |
816 | } | |
817 | ------------ | |
818 | ||
819 | == Example Trace2 API Usage | |
820 | ||
821 | Here is a hypothetical usage of the Trace2 API showing the intended | |
822 | usage (without worrying about the actual Git details). | |
823 | ||
824 | Initialization:: | |
825 | ||
826 | Initialization happens in `main()`. Behind the scenes, an | |
827 | `atexit` and `signal` handler are registered. | |
828 | + | |
829 | ---------------- | |
830 | int main(int argc, const char **argv) | |
831 | { | |
832 | int exit_code; | |
833 | ||
834 | trace2_initialize(); | |
835 | trace2_cmd_start(argv); | |
836 | ||
837 | exit_code = cmd_main(argc, argv); | |
838 | ||
839 | trace2_cmd_exit(exit_code); | |
840 | ||
841 | return exit_code; | |
842 | } | |
843 | ---------------- | |
844 | ||
845 | Command Details:: | |
846 | ||
847 | After the basics are established, additional command | |
848 | information can be sent to Trace2 as it is discovered. | |
849 | + | |
850 | ---------------- | |
851 | int cmd_checkout(int argc, const char **argv) | |
852 | { | |
853 | trace2_cmd_name("checkout"); | |
854 | trace2_cmd_mode("branch"); | |
855 | trace2_def_repo(the_repository); | |
856 | ||
857 | // emit "def_param" messages for "interesting" config settings. | |
858 | trace2_cmd_list_config(); | |
859 | ||
860 | if (do_something()) | |
861 | trace2_cmd_error("Path '%s': cannot do something", path); | |
862 | ||
863 | return 0; | |
864 | } | |
865 | ---------------- | |
866 | ||
867 | Child Processes:: | |
868 | ||
869 | Wrap code spawning child processes. | |
870 | + | |
871 | ---------------- | |
872 | void run_child(...) | |
873 | { | |
874 | int child_exit_code; | |
875 | struct child_process cmd = CHILD_PROCESS_INIT; | |
876 | ... | |
877 | cmd.trace2_child_class = "editor"; | |
878 | ||
879 | trace2_child_start(&cmd); | |
880 | child_exit_code = spawn_child_and_wait_for_it(); | |
881 | trace2_child_exit(&cmd, child_exit_code); | |
882 | } | |
883 | ---------------- | |
884 | + | |
885 | For example, the following fetch command spawned ssh, index-pack, | |
886 | rev-list, and gc. This example also shows that fetch took | |
887 | 5.199 seconds and of that 4.932 was in ssh. | |
888 | + | |
889 | ---------------- | |
e4b75d6a SG |
890 | $ export GIT_TRACE2_BRIEF=1 |
891 | $ export GIT_TRACE2=~/log.normal | |
e544221d JH |
892 | $ git fetch origin |
893 | ... | |
894 | ---------------- | |
895 | + | |
896 | ---------------- | |
897 | $ cat ~/log.normal | |
898 | version 2.20.1.vfs.1.1.47.g534dbe1ad1 | |
899 | start git fetch origin | |
900 | worktree /Users/jeffhost/work/gfw | |
901 | cmd_name fetch (fetch) | |
902 | child_start[0] ssh git@github.com ... | |
903 | child_start[1] git index-pack ... | |
904 | ... (Trace2 events from child processes omitted) | |
905 | child_exit[1] pid:14707 code:0 elapsed:0.076353 | |
906 | child_exit[0] pid:14706 code:0 elapsed:4.931869 | |
907 | child_start[2] git rev-list ... | |
908 | ... (Trace2 events from child process omitted) | |
909 | child_exit[2] pid:14708 code:0 elapsed:0.110605 | |
910 | child_start[3] git gc --auto | |
911 | ... (Trace2 events from child process omitted) | |
912 | child_exit[3] pid:14709 code:0 elapsed:0.006240 | |
913 | exit elapsed:5.198503 code:0 | |
914 | atexit elapsed:5.198541 code:0 | |
915 | ---------------- | |
916 | + | |
917 | When a git process is a (direct or indirect) child of another | |
918 | git process, it inherits Trace2 context information. This | |
919 | allows the child to print the command hierarchy. This example | |
920 | shows gc as child[3] of fetch. When the gc process reports | |
921 | its name as "gc", it also reports the hierarchy as "fetch/gc". | |
922 | (In this example, trace2 messages from the child process is | |
923 | indented for clarity.) | |
924 | + | |
925 | ---------------- | |
e4b75d6a SG |
926 | $ export GIT_TRACE2_BRIEF=1 |
927 | $ export GIT_TRACE2=~/log.normal | |
e544221d JH |
928 | $ git fetch origin |
929 | ... | |
930 | ---------------- | |
931 | + | |
932 | ---------------- | |
933 | $ cat ~/log.normal | |
934 | version 2.20.1.160.g5676107ecd.dirty | |
935 | start git fetch official | |
936 | worktree /Users/jeffhost/work/gfw | |
937 | cmd_name fetch (fetch) | |
938 | ... | |
939 | child_start[3] git gc --auto | |
940 | version 2.20.1.160.g5676107ecd.dirty | |
941 | start /Users/jeffhost/work/gfw/git gc --auto | |
942 | worktree /Users/jeffhost/work/gfw | |
943 | cmd_name gc (fetch/gc) | |
944 | exit elapsed:0.001959 code:0 | |
945 | atexit elapsed:0.001997 code:0 | |
946 | child_exit[3] pid:20303 code:0 elapsed:0.007564 | |
947 | exit elapsed:3.868938 code:0 | |
948 | atexit elapsed:3.868970 code:0 | |
949 | ---------------- | |
950 | ||
951 | Regions:: | |
952 | ||
3188d3c0 | 953 | Regions can be used to time an interesting section of code. |
e544221d JH |
954 | + |
955 | ---------------- | |
956 | void wt_status_collect(struct wt_status *s) | |
957 | { | |
958 | trace2_region_enter("status", "worktrees", s->repo); | |
959 | wt_status_collect_changes_worktree(s); | |
960 | trace2_region_leave("status", "worktrees", s->repo); | |
961 | ||
962 | trace2_region_enter("status", "index", s->repo); | |
963 | wt_status_collect_changes_index(s); | |
964 | trace2_region_leave("status", "index", s->repo); | |
965 | ||
966 | trace2_region_enter("status", "untracked", s->repo); | |
967 | wt_status_collect_untracked(s); | |
968 | trace2_region_leave("status", "untracked", s->repo); | |
969 | } | |
970 | ||
971 | void wt_status_print(struct wt_status *s) | |
972 | { | |
973 | trace2_region_enter("status", "print", s->repo); | |
974 | switch (s->status_format) { | |
975 | ... | |
976 | } | |
977 | trace2_region_leave("status", "print", s->repo); | |
978 | } | |
979 | ---------------- | |
980 | + | |
981 | In this example, scanning for untracked files ran from +0.012568 to | |
982 | +0.027149 (since the process started) and took 0.014581 seconds. | |
983 | + | |
984 | ---------------- | |
e4b75d6a SG |
985 | $ export GIT_TRACE2_PERF_BRIEF=1 |
986 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
987 | $ git status |
988 | ... | |
989 | ||
990 | $ cat ~/log.perf | |
991 | d0 | main | version | | | | | 2.20.1.160.g5676107ecd.dirty | |
39f43177 | 992 | d0 | main | start | | 0.001173 | | | git status |
e544221d JH |
993 | d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw |
994 | d0 | main | cmd_name | | | | | status (status) | |
995 | ... | |
996 | d0 | main | region_enter | r1 | 0.010988 | | status | label:worktrees | |
997 | d0 | main | region_leave | r1 | 0.011236 | 0.000248 | status | label:worktrees | |
998 | d0 | main | region_enter | r1 | 0.011260 | | status | label:index | |
999 | d0 | main | region_leave | r1 | 0.012542 | 0.001282 | status | label:index | |
1000 | d0 | main | region_enter | r1 | 0.012568 | | status | label:untracked | |
1001 | d0 | main | region_leave | r1 | 0.027149 | 0.014581 | status | label:untracked | |
1002 | d0 | main | region_enter | r1 | 0.027411 | | status | label:print | |
1003 | d0 | main | region_leave | r1 | 0.028741 | 0.001330 | status | label:print | |
1004 | d0 | main | exit | | 0.028778 | | | code:0 | |
1005 | d0 | main | atexit | | 0.028809 | | | code:0 | |
1006 | ---------------- | |
1007 | + | |
1008 | Regions may be nested. This causes messages to be indented in the | |
1009 | PERF target, for example. | |
031fd4b9 | 1010 | Elapsed times are relative to the start of the corresponding nesting |
e544221d JH |
1011 | level as expected. For example, if we add region message to: |
1012 | + | |
1013 | ---------------- | |
1014 | static enum path_treatment read_directory_recursive(struct dir_struct *dir, | |
1015 | struct index_state *istate, const char *base, int baselen, | |
1016 | struct untracked_cache_dir *untracked, int check_only, | |
1017 | int stop_at_first_file, const struct pathspec *pathspec) | |
1018 | { | |
1019 | enum path_treatment state, subdir_state, dir_state = path_none; | |
1020 | ||
1021 | trace2_region_enter_printf("dir", "read_recursive", NULL, "%.*s", baselen, base); | |
1022 | ... | |
1023 | trace2_region_leave_printf("dir", "read_recursive", NULL, "%.*s", baselen, base); | |
1024 | return dir_state; | |
1025 | } | |
1026 | ---------------- | |
1027 | + | |
1028 | We can further investigate the time spent scanning for untracked files. | |
1029 | + | |
1030 | ---------------- | |
e4b75d6a SG |
1031 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1032 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1033 | $ git status |
1034 | ... | |
1035 | $ cat ~/log.perf | |
1036 | d0 | main | version | | | | | 2.20.1.162.gb4ccea44db.dirty | |
39f43177 | 1037 | d0 | main | start | | 0.001173 | | | git status |
e544221d JH |
1038 | d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw |
1039 | d0 | main | cmd_name | | | | | status (status) | |
1040 | ... | |
1041 | d0 | main | region_enter | r1 | 0.015047 | | status | label:untracked | |
1042 | d0 | main | region_enter | | 0.015132 | | dir | ..label:read_recursive | |
1043 | d0 | main | region_enter | | 0.016341 | | dir | ....label:read_recursive vcs-svn/ | |
1044 | d0 | main | region_leave | | 0.016422 | 0.000081 | dir | ....label:read_recursive vcs-svn/ | |
1045 | d0 | main | region_enter | | 0.016446 | | dir | ....label:read_recursive xdiff/ | |
1046 | d0 | main | region_leave | | 0.016522 | 0.000076 | dir | ....label:read_recursive xdiff/ | |
1047 | d0 | main | region_enter | | 0.016612 | | dir | ....label:read_recursive git-gui/ | |
1048 | d0 | main | region_enter | | 0.016698 | | dir | ......label:read_recursive git-gui/po/ | |
1049 | d0 | main | region_enter | | 0.016810 | | dir | ........label:read_recursive git-gui/po/glossary/ | |
1050 | d0 | main | region_leave | | 0.016863 | 0.000053 | dir | ........label:read_recursive git-gui/po/glossary/ | |
1051 | ... | |
1052 | d0 | main | region_enter | | 0.031876 | | dir | ....label:read_recursive builtin/ | |
1053 | d0 | main | region_leave | | 0.032270 | 0.000394 | dir | ....label:read_recursive builtin/ | |
1054 | d0 | main | region_leave | | 0.032414 | 0.017282 | dir | ..label:read_recursive | |
1055 | d0 | main | region_leave | r1 | 0.032454 | 0.017407 | status | label:untracked | |
1056 | ... | |
1057 | d0 | main | exit | | 0.034279 | | | code:0 | |
1058 | d0 | main | atexit | | 0.034322 | | | code:0 | |
1059 | ---------------- | |
1060 | + | |
1061 | Trace2 regions are similar to the existing trace_performance_enter() | |
1062 | and trace_performance_leave() routines, but are thread safe and | |
1063 | maintain per-thread stacks of timers. | |
1064 | ||
1065 | Data Messages:: | |
1066 | ||
1067 | Data messages added to a region. | |
1068 | + | |
1069 | ---------------- | |
1070 | int read_index_from(struct index_state *istate, const char *path, | |
1071 | const char *gitdir) | |
1072 | { | |
1073 | trace2_region_enter_printf("index", "do_read_index", the_repository, "%s", path); | |
1074 | ||
1075 | ... | |
1076 | ||
1077 | trace2_data_intmax("index", the_repository, "read/version", istate->version); | |
1078 | trace2_data_intmax("index", the_repository, "read/cache_nr", istate->cache_nr); | |
1079 | ||
1080 | trace2_region_leave_printf("index", "do_read_index", the_repository, "%s", path); | |
1081 | } | |
1082 | ---------------- | |
1083 | + | |
1084 | This example shows that the index contained 3552 entries. | |
1085 | + | |
1086 | ---------------- | |
e4b75d6a SG |
1087 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1088 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1089 | $ git status |
1090 | ... | |
1091 | $ cat ~/log.perf | |
1092 | d0 | main | version | | | | | 2.20.1.156.gf9916ae094.dirty | |
39f43177 | 1093 | d0 | main | start | | 0.001173 | | | git status |
e544221d JH |
1094 | d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw |
1095 | d0 | main | cmd_name | | | | | status (status) | |
1096 | d0 | main | region_enter | r1 | 0.001791 | | index | label:do_read_index .git/index | |
1097 | d0 | main | data | r1 | 0.002494 | 0.000703 | index | ..read/version:2 | |
1098 | d0 | main | data | r1 | 0.002520 | 0.000729 | index | ..read/cache_nr:3552 | |
1099 | d0 | main | region_leave | r1 | 0.002539 | 0.000748 | index | label:do_read_index .git/index | |
1100 | ... | |
1101 | ---------------- | |
1102 | ||
1103 | Thread Events:: | |
1104 | ||
1105 | Thread messages added to a thread-proc. | |
1106 | + | |
3188d3c0 | 1107 | For example, the multi-threaded preload-index code can be |
e544221d | 1108 | instrumented with a region around the thread pool and then |
3188d3c0 | 1109 | per-thread start and exit events within the thread-proc. |
e544221d JH |
1110 | + |
1111 | ---------------- | |
1112 | static void *preload_thread(void *_data) | |
1113 | { | |
1114 | // start the per-thread clock and emit a message. | |
1115 | trace2_thread_start("preload_thread"); | |
1116 | ||
1117 | // report which chunk of the array this thread was assigned. | |
1118 | trace2_data_intmax("index", the_repository, "offset", p->offset); | |
1119 | trace2_data_intmax("index", the_repository, "count", nr); | |
1120 | ||
1121 | do { | |
1122 | ... | |
1123 | } while (--nr > 0); | |
1124 | ... | |
1125 | ||
1126 | // report elapsed time taken by this thread. | |
1127 | trace2_thread_exit(); | |
1128 | return NULL; | |
1129 | } | |
1130 | ||
1131 | void preload_index(struct index_state *index, | |
1132 | const struct pathspec *pathspec, | |
1133 | unsigned int refresh_flags) | |
1134 | { | |
1135 | trace2_region_enter("index", "preload", the_repository); | |
1136 | ||
1137 | for (i = 0; i < threads; i++) { | |
1138 | ... /* create thread */ | |
1139 | } | |
1140 | ||
1141 | for (i = 0; i < threads; i++) { | |
1142 | ... /* join thread */ | |
1143 | } | |
1144 | ||
1145 | trace2_region_leave("index", "preload", the_repository); | |
1146 | } | |
1147 | ---------------- | |
1148 | + | |
1149 | In this example preload_index() was executed by the `main` thread | |
1150 | and started the `preload` region. Seven threads, named | |
1151 | `th01:preload_thread` through `th07:preload_thread`, were started. | |
1152 | Events from each thread are atomically appended to the shared target | |
1153 | stream as they occur so they may appear in random order with respect | |
1154 | other threads. Finally, the main thread waits for the threads to | |
1155 | finish and leaves the region. | |
1156 | + | |
1157 | Data events are tagged with the active thread name. They are used | |
1158 | to report the per-thread parameters. | |
1159 | + | |
1160 | ---------------- | |
e4b75d6a SG |
1161 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1162 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1163 | $ git status |
1164 | ... | |
1165 | $ cat ~/log.perf | |
1166 | ... | |
1167 | d0 | main | region_enter | r1 | 0.002595 | | index | label:preload | |
1168 | d0 | th01:preload_thread | thread_start | | 0.002699 | | | | |
1169 | d0 | th02:preload_thread | thread_start | | 0.002721 | | | | |
1170 | d0 | th01:preload_thread | data | r1 | 0.002736 | 0.000037 | index | offset:0 | |
1171 | d0 | th02:preload_thread | data | r1 | 0.002751 | 0.000030 | index | offset:2032 | |
1172 | d0 | th03:preload_thread | thread_start | | 0.002711 | | | | |
1173 | d0 | th06:preload_thread | thread_start | | 0.002739 | | | | |
1174 | d0 | th01:preload_thread | data | r1 | 0.002766 | 0.000067 | index | count:508 | |
1175 | d0 | th06:preload_thread | data | r1 | 0.002856 | 0.000117 | index | offset:2540 | |
1176 | d0 | th03:preload_thread | data | r1 | 0.002824 | 0.000113 | index | offset:1016 | |
1177 | d0 | th04:preload_thread | thread_start | | 0.002710 | | | | |
1178 | d0 | th02:preload_thread | data | r1 | 0.002779 | 0.000058 | index | count:508 | |
1179 | d0 | th06:preload_thread | data | r1 | 0.002966 | 0.000227 | index | count:508 | |
1180 | d0 | th07:preload_thread | thread_start | | 0.002741 | | | | |
1181 | d0 | th07:preload_thread | data | r1 | 0.003017 | 0.000276 | index | offset:3048 | |
1182 | d0 | th05:preload_thread | thread_start | | 0.002712 | | | | |
1183 | d0 | th05:preload_thread | data | r1 | 0.003067 | 0.000355 | index | offset:1524 | |
1184 | d0 | th05:preload_thread | data | r1 | 0.003090 | 0.000378 | index | count:508 | |
1185 | d0 | th07:preload_thread | data | r1 | 0.003037 | 0.000296 | index | count:504 | |
1186 | d0 | th03:preload_thread | data | r1 | 0.002971 | 0.000260 | index | count:508 | |
1187 | d0 | th04:preload_thread | data | r1 | 0.002983 | 0.000273 | index | offset:508 | |
1188 | d0 | th04:preload_thread | data | r1 | 0.007311 | 0.004601 | index | count:508 | |
1189 | d0 | th05:preload_thread | thread_exit | | 0.008781 | 0.006069 | | | |
1190 | d0 | th01:preload_thread | thread_exit | | 0.009561 | 0.006862 | | | |
1191 | d0 | th03:preload_thread | thread_exit | | 0.009742 | 0.007031 | | | |
1192 | d0 | th06:preload_thread | thread_exit | | 0.009820 | 0.007081 | | | |
1193 | d0 | th02:preload_thread | thread_exit | | 0.010274 | 0.007553 | | | |
1194 | d0 | th07:preload_thread | thread_exit | | 0.010477 | 0.007736 | | | |
1195 | d0 | th04:preload_thread | thread_exit | | 0.011657 | 0.008947 | | | |
1196 | d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload | |
1197 | ... | |
1198 | d0 | main | exit | | 0.029996 | | | code:0 | |
1199 | d0 | main | atexit | | 0.030027 | | | code:0 | |
1200 | ---------------- | |
1201 | + | |
1202 | In this example, the preload region took 0.009122 seconds. The 7 threads | |
1203 | took between 0.006069 and 0.008947 seconds to work on their portion of | |
1204 | the index. Thread "th01" worked on 508 items at offset 0. Thread "th02" | |
031fd4b9 | 1205 | worked on 508 items at offset 2032. Thread "th04" worked on 508 items |
e544221d JH |
1206 | at offset 508. |
1207 | + | |
1208 | This example also shows that thread names are assigned in a racy manner | |
1209 | as each thread starts and allocates TLS storage. | |
1210 | ||
050d0dc2 TL |
1211 | Config (def param) Events:: |
1212 | ||
1213 | Dump "interesting" config values to trace2 log. | |
1214 | + | |
1215 | We can optionally emit configuration events, see | |
1216 | `trace2.configparams` in linkgit:git-config[1] for how to enable | |
1217 | it. | |
1218 | + | |
1219 | ---------------- | |
35ae40ea TL |
1220 | $ git config --system color.ui never |
1221 | $ git config --global color.ui always | |
1222 | $ git config --local color.ui auto | |
1223 | $ git config --list --show-scope | grep 'color.ui' | |
1224 | system color.ui=never | |
1225 | global color.ui=always | |
1226 | local color.ui=auto | |
050d0dc2 TL |
1227 | ---------------- |
1228 | + | |
1229 | Then, mark the config `color.ui` as "interesting" config with | |
1230 | `GIT_TRACE2_CONFIG_PARAMS`: | |
1231 | + | |
1232 | ---------------- | |
1233 | $ export GIT_TRACE2_PERF_BRIEF=1 | |
1234 | $ export GIT_TRACE2_PERF=~/log.perf | |
1235 | $ export GIT_TRACE2_CONFIG_PARAMS=color.ui | |
1236 | $ git version | |
1237 | ... | |
1238 | $ cat ~/log.perf | |
1239 | d0 | main | version | | | | | ... | |
1240 | d0 | main | start | | 0.001642 | | | /usr/local/bin/git version | |
1241 | d0 | main | cmd_name | | | | | version (version) | |
35ae40ea TL |
1242 | d0 | main | def_param | | | | scope:system | color.ui:never |
1243 | d0 | main | def_param | | | | scope:global | color.ui:always | |
1244 | d0 | main | def_param | | | | scope:local | color.ui:auto | |
050d0dc2 TL |
1245 | d0 | main | data | r0 | 0.002100 | 0.002100 | fsync | fsync/writeout-only:0 |
1246 | d0 | main | data | r0 | 0.002126 | 0.002126 | fsync | fsync/hardware-flush:0 | |
35ae40ea TL |
1247 | d0 | main | exit | | 0.000470 | | | code:0 |
1248 | d0 | main | atexit | | 0.000477 | | | code:0 | |
050d0dc2 | 1249 | ---------------- |
e544221d JH |
1250 | == Future Work |
1251 | ||
1252 | === Relationship to the Existing Trace Api (api-trace.txt) | |
1253 | ||
1254 | There are a few issues to resolve before we can completely | |
1255 | switch to Trace2. | |
1256 | ||
1c538b95 | 1257 | * Updating existing tests that assume `GIT_TRACE` format messages. |
e544221d | 1258 | |
1c538b95 | 1259 | * How to best handle custom `GIT_TRACE_<key>` messages? |
e544221d | 1260 | |
1c538b95 | 1261 | ** The `GIT_TRACE_<key>` mechanism allows each <key> to write to a |
e544221d JH |
1262 | different file (in addition to just stderr). |
1263 | ||
1264 | ** Do we want to maintain that ability or simply write to the existing | |
1265 | Trace2 targets (and convert <key> to a "category"). |