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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 | ||
8e8c5ad2 JH |
151 | The Trace2 public API is defined and documented in `trace2.h`; refer to it for |
152 | more information. All public functions and macros are prefixed | |
153 | with `trace2_` and are implemented in `trace2.c`. | |
e544221d JH |
154 | |
155 | There are no public Trace2 data structures. | |
156 | ||
157 | The Trace2 code also defines a set of private functions and data types | |
158 | in the `trace2/` directory. These symbols are prefixed with `tr2_` | |
8e8c5ad2 JH |
159 | and should only be used by functions in `trace2.c` (or other private |
160 | source files in `trace2/`). | |
e544221d | 161 | |
8e8c5ad2 | 162 | === Conventions for Public Functions and Macros |
e544221d JH |
163 | |
164 | Some functions have a `_fl()` suffix to indicate that they take `file` | |
165 | and `line-number` arguments. | |
166 | ||
167 | Some functions have a `_va_fl()` suffix to indicate that they also | |
168 | take a `va_list` argument. | |
169 | ||
170 | Some functions have a `_printf_fl()` suffix to indicate that they also | |
236d1177 | 171 | take a `printf()` style format with a variable number of arguments. |
e544221d | 172 | |
8e8c5ad2 | 173 | CPP wrapper macros are defined to hide most of these details. |
e544221d JH |
174 | |
175 | == Trace2 Target Formats | |
176 | ||
177 | === NORMAL Format | |
178 | ||
e544221d JH |
179 | Events are written as lines of the form: |
180 | ||
181 | ------------ | |
182 | [<time> SP <filename>:<line> SP+] <event-name> [[SP] <event-message>] LF | |
183 | ------------ | |
184 | ||
185 | `<event-name>`:: | |
186 | ||
187 | is the event name. | |
188 | ||
189 | `<event-message>`:: | |
c191b918 | 190 | is a free-form `printf()` message intended for human consumption. |
e544221d JH |
191 | + |
192 | Note that this may contain embedded LF or CRLF characters that are | |
193 | not escaped, so the event may spill across multiple lines. | |
194 | ||
e4b75d6a | 195 | If `GIT_TRACE2_BRIEF` or `trace2.normalBrief` is true, the `time`, `filename`, |
81567caf | 196 | and `line` fields are omitted. |
e544221d JH |
197 | |
198 | This target is intended to be more of a summary (like GIT_TRACE) and | |
199 | less detailed than the other targets. It ignores thread, region, and | |
200 | data messages, for example. | |
201 | ||
202 | === PERF Format | |
203 | ||
e544221d JH |
204 | Events are written as lines of the form: |
205 | ||
206 | ------------ | |
207 | [<time> SP <filename>:<line> SP+ | |
208 | BAR SP] d<depth> SP | |
209 | BAR SP <thread-name> SP+ | |
210 | BAR SP <event-name> SP+ | |
211 | BAR SP [r<repo-id>] SP+ | |
212 | BAR SP [<t_abs>] SP+ | |
213 | BAR SP [<t_rel>] SP+ | |
214 | BAR SP [<category>] SP+ | |
215 | BAR SP DOTS* <perf-event-message> | |
216 | LF | |
217 | ------------ | |
218 | ||
219 | `<depth>`:: | |
220 | is the git process depth. This is the number of parent | |
221 | git processes. A top-level git command has depth value "d0". | |
222 | A child of it has depth value "d1". A second level child | |
223 | has depth value "d2" and so on. | |
224 | ||
225 | `<thread-name>`:: | |
226 | is a unique name for the thread. The primary thread | |
227 | is called "main". Other thread names are of the form "th%d:%s" | |
228 | and include a unique number and the name of the thread-proc. | |
229 | ||
230 | `<event-name>`:: | |
231 | is the event name. | |
232 | ||
233 | `<repo-id>`:: | |
234 | when present, is a number indicating the repository | |
235 | in use. A `def_repo` event is emitted when a repository is | |
236 | opened. This defines the repo-id and associated worktree. | |
237 | Subsequent repo-specific events will reference this repo-id. | |
238 | + | |
239 | Currently, this is always "r1" for the main repository. | |
240 | This field is in anticipation of in-proc submodules in the future. | |
241 | ||
242 | `<t_abs>`:: | |
243 | when present, is the absolute time in seconds since the | |
244 | program started. | |
245 | ||
246 | `<t_rel>`:: | |
247 | when present, is time in seconds relative to the start of | |
248 | the current region. For a thread-exit event, it is the elapsed | |
249 | time of the thread. | |
250 | ||
251 | `<category>`:: | |
252 | is present on region and data events and is used to | |
253 | indicate a broad category, such as "index" or "status". | |
254 | ||
255 | `<perf-event-message>`:: | |
c191b918 | 256 | is a free-form `printf()` message intended for human consumption. |
e544221d JH |
257 | |
258 | ------------ | |
259 | 15:33:33.532712 wt-status.c:2310 | d0 | main | region_enter | r1 | 0.126064 | | status | label:print | |
260 | 15:33:33.532712 wt-status.c:2331 | d0 | main | region_leave | r1 | 0.127568 | 0.001504 | status | label:print | |
261 | ------------ | |
262 | ||
e4b75d6a | 263 | If `GIT_TRACE2_PERF_BRIEF` or `trace2.perfBrief` is true, the `time`, `file`, |
81567caf | 264 | and `line` fields are omitted. |
e544221d JH |
265 | |
266 | ------------ | |
267 | d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload | |
268 | ------------ | |
269 | ||
270 | The PERF target is intended for interactive performance analysis | |
271 | during development and is quite noisy. | |
272 | ||
273 | === EVENT Format | |
274 | ||
e544221d JH |
275 | Each event is a JSON-object containing multiple key/value pairs |
276 | written as a single line and followed by a LF. | |
277 | ||
278 | ------------ | |
279 | '{' <key> ':' <value> [',' <key> ':' <value>]* '}' LF | |
280 | ------------ | |
281 | ||
282 | Some key/value pairs are common to all events and some are | |
283 | event-specific. | |
284 | ||
285 | ==== Common Key/Value Pairs | |
286 | ||
287 | The following key/value pairs are common to all events: | |
288 | ||
289 | ------------ | |
290 | { | |
291 | "event":"version", | |
81567caf | 292 | "sid":"20190408T191827.272759Z-H9b68c35f-P00003510", |
e544221d | 293 | "thread":"main", |
08881b9a | 294 | "time":"2019-04-08T19:18:27.282761Z", |
e544221d | 295 | "file":"common-main.c", |
08881b9a | 296 | "line":42, |
e544221d JH |
297 | ... |
298 | } | |
299 | ------------ | |
300 | ||
301 | `"event":<event>`:: | |
302 | is the event name. | |
303 | ||
304 | `"sid":<sid>`:: | |
305 | is the session-id. This is a unique string to identify the | |
306 | process instance to allow all events emitted by a process to | |
307 | be identified. A session-id is used instead of a PID because | |
308 | PIDs are recycled by the OS. For child git processes, the | |
309 | session-id is prepended with the session-id of the parent git | |
310 | process to allow parent-child relationships to be identified | |
311 | during post-processing. | |
312 | ||
313 | `"thread":<thread>`:: | |
314 | is the thread name. | |
315 | ||
316 | `"time":<time>`:: | |
317 | is the UTC time of the event. | |
318 | ||
319 | `"file":<filename>`:: | |
320 | is source file generating the event. | |
321 | ||
322 | `"line":<line-number>`:: | |
323 | is the integer source line number generating the event. | |
324 | ||
325 | `"repo":<repo-id>`:: | |
326 | when present, is the integer repo-id as described previously. | |
327 | ||
e4b75d6a | 328 | If `GIT_TRACE2_EVENT_BRIEF` or `trace2.eventBrief` is true, the `file` |
81567caf JH |
329 | and `line` fields are omitted from all events and the `time` field is |
330 | only present on the "start" and "atexit" events. | |
e544221d JH |
331 | |
332 | ==== Event-Specific Key/Value Pairs | |
333 | ||
334 | `"version"`:: | |
22541013 JS |
335 | This event gives the version of the executable and the EVENT format. It |
336 | should always be the first event in a trace session. The EVENT format | |
337 | version will be incremented if new event types are added, if existing | |
338 | fields are removed, or if there are significant changes in | |
339 | interpretation of existing events or fields. Smaller changes, such as | |
340 | adding a new field to an existing event, will not require an increment | |
341 | to the EVENT format version. | |
e544221d JH |
342 | + |
343 | ------------ | |
344 | { | |
345 | "event":"version", | |
346 | ... | |
04480e67 | 347 | "evt":"3", # EVENT format version |
e544221d JH |
348 | "exe":"2.20.1.155.g426c96fcdb" # git version |
349 | } | |
350 | ------------ | |
351 | ||
7ba68e0c | 352 | `"too_many_files"`:: |
87db61a4 JS |
353 | This event is written to the git-trace2-discard sentinel file if there |
354 | are too many files in the target trace directory (see the | |
355 | trace2.maxFiles config option). | |
356 | + | |
357 | ------------ | |
358 | { | |
7ba68e0c | 359 | "event":"too_many_files", |
87db61a4 JS |
360 | ... |
361 | } | |
362 | ------------ | |
363 | ||
e544221d JH |
364 | `"start"`:: |
365 | This event contains the complete argv received by main(). | |
366 | + | |
367 | ------------ | |
368 | { | |
369 | "event":"start", | |
370 | ... | |
39f43177 | 371 | "t_abs":0.001227, # elapsed time in seconds |
e544221d JH |
372 | "argv":["git","version"] |
373 | } | |
374 | ------------ | |
375 | ||
376 | `"exit"`:: | |
377 | This event is emitted when git calls `exit()`. | |
378 | + | |
379 | ------------ | |
380 | { | |
381 | "event":"exit", | |
382 | ... | |
383 | "t_abs":0.001227, # elapsed time in seconds | |
384 | "code":0 # exit code | |
385 | } | |
386 | ------------ | |
387 | ||
388 | `"atexit"`:: | |
389 | This event is emitted by the Trace2 `atexit` routine during | |
390 | final shutdown. It should be the last event emitted by the | |
391 | process. | |
392 | + | |
393 | (The elapsed time reported here is greater than the time reported in | |
394 | the "exit" event because it runs after all other atexit tasks have | |
395 | completed.) | |
396 | + | |
397 | ------------ | |
398 | { | |
399 | "event":"atexit", | |
400 | ... | |
401 | "t_abs":0.001227, # elapsed time in seconds | |
402 | "code":0 # exit code | |
403 | } | |
404 | ------------ | |
405 | ||
406 | `"signal"`:: | |
407 | This event is emitted when the program is terminated by a user | |
408 | signal. Depending on the platform, the signal event may | |
409 | prevent the "atexit" event from being generated. | |
410 | + | |
411 | ------------ | |
412 | { | |
413 | "event":"signal", | |
414 | ... | |
415 | "t_abs":0.001227, # elapsed time in seconds | |
24df0d49 | 416 | "signo":13 # SIGTERM, SIGINT, etc. |
e544221d JH |
417 | } |
418 | ------------ | |
419 | ||
420 | `"error"`:: | |
0cc05b04 ÆAB |
421 | This event is emitted when one of the `BUG()`, `bug()`, `error()`, |
422 | `die()`, `warning()`, or `usage()` functions are called. | |
e544221d JH |
423 | + |
424 | ------------ | |
425 | { | |
426 | "event":"error", | |
427 | ... | |
428 | "msg":"invalid option: --cahced", # formatted error message | |
429 | "fmt":"invalid option: %s" # error format string | |
430 | } | |
431 | ------------ | |
432 | + | |
433 | The error event may be emitted more than once. The format string | |
434 | allows post-processors to group errors by type without worrying | |
435 | about specific error arguments. | |
436 | ||
437 | `"cmd_path"`:: | |
438 | This event contains the discovered full path of the git | |
439 | executable (on platforms that are configured to resolve it). | |
440 | + | |
441 | ------------ | |
442 | { | |
443 | "event":"cmd_path", | |
444 | ... | |
445 | "path":"C:/work/gfw/git.exe" | |
446 | } | |
447 | ------------ | |
448 | ||
2f732bf1 ES |
449 | `"cmd_ancestry"`:: |
450 | This event contains the text command name for the parent (and earlier | |
451 | generations of parents) of the current process, in an array ordered from | |
452 | nearest parent to furthest great-grandparent. It may not be implemented | |
453 | on all platforms. | |
454 | + | |
455 | ------------ | |
456 | { | |
457 | "event":"cmd_ancestry", | |
458 | ... | |
459 | "ancestry":["bash","tmux: server","systemd"] | |
460 | } | |
461 | ------------ | |
462 | ||
e544221d JH |
463 | `"cmd_name"`:: |
464 | This event contains the command name for this git process | |
465 | and the hierarchy of commands from parent git processes. | |
466 | + | |
467 | ------------ | |
468 | { | |
469 | "event":"cmd_name", | |
470 | ... | |
471 | "name":"pack-objects", | |
472 | "hierarchy":"push/pack-objects" | |
473 | } | |
474 | ------------ | |
475 | + | |
476 | Normally, the "name" field contains the canonical name of the | |
477 | command. When a canonical name is not available, one of | |
478 | these special values are used: | |
479 | + | |
480 | ------------ | |
481 | "_query_" # "git --html-path" | |
482 | "_run_dashed_" # when "git foo" tries to run "git-foo" | |
483 | "_run_shell_alias_" # alias expansion to a shell command | |
484 | "_run_git_alias_" # alias expansion to a git command | |
485 | "_usage_" # usage error | |
486 | ------------ | |
487 | ||
488 | `"cmd_mode"`:: | |
a6c80c31 | 489 | This event, when present, describes the command variant. This |
e544221d JH |
490 | event may be emitted more than once. |
491 | + | |
492 | ------------ | |
493 | { | |
494 | "event":"cmd_mode", | |
495 | ... | |
496 | "name":"branch" | |
497 | } | |
498 | ------------ | |
499 | + | |
500 | The "name" field is an arbitrary string to describe the command mode. | |
501 | For example, checkout can checkout a branch or an individual file. | |
502 | And these variations typically have different performance | |
503 | characteristics that are not comparable. | |
504 | ||
505 | `"alias"`:: | |
506 | This event is present when an alias is expanded. | |
507 | + | |
508 | ------------ | |
509 | { | |
510 | "event":"alias", | |
511 | ... | |
512 | "alias":"l", # registered alias | |
513 | "argv":["log","--graph"] # alias expansion | |
514 | } | |
515 | ------------ | |
516 | ||
517 | `"child_start"`:: | |
518 | This event describes a child process that is about to be | |
519 | spawned. | |
520 | + | |
521 | ------------ | |
522 | { | |
523 | "event":"child_start", | |
524 | ... | |
525 | "child_id":2, | |
526 | "child_class":"?", | |
527 | "use_shell":false, | |
528 | "argv":["git","rev-list","--objects","--stdin","--not","--all","--quiet"] | |
529 | ||
530 | "hook_name":"<hook_name>" # present when child_class is "hook" | |
531 | "cd":"<path>" # present when cd is required | |
532 | } | |
533 | ------------ | |
534 | + | |
535 | The "child_id" field can be used to match this child_start with the | |
536 | corresponding child_exit event. | |
537 | + | |
538 | The "child_class" field is a rough classification, such as "editor", | |
539 | "pager", "transport/*", and "hook". Unclassified children are classified | |
540 | with "?". | |
541 | ||
542 | `"child_exit"`:: | |
543 | This event is generated after the current process has returned | |
c191b918 | 544 | from the `waitpid()` and collected the exit information from the |
e544221d JH |
545 | child. |
546 | + | |
547 | ------------ | |
548 | { | |
549 | "event":"child_exit", | |
550 | ... | |
551 | "child_id":2, | |
552 | "pid":14708, # child PID | |
553 | "code":0, # child exit-code | |
554 | "t_rel":0.110605 # observed run-time of child process | |
555 | } | |
556 | ------------ | |
557 | + | |
558 | Note that the session-id of the child process is not available to | |
559 | the current/spawning process, so the child's PID is reported here as | |
560 | a hint for post-processing. (But it is only a hint because the child | |
031fd4b9 | 561 | process may be a shell script which doesn't have a session-id.) |
e544221d JH |
562 | + |
563 | Note that the `t_rel` field contains the observed run time in seconds | |
564 | for the child process (starting before the fork/exec/spawn and | |
c191b918 | 565 | stopping after the `waitpid()` and includes OS process creation overhead). |
e544221d JH |
566 | So this time will be slightly larger than the atexit time reported by |
567 | the child process itself. | |
568 | ||
64bc7524 JH |
569 | `"child_ready"`:: |
570 | This event is generated after the current process has started | |
571 | a background process and released all handles to it. | |
572 | + | |
573 | ------------ | |
574 | { | |
575 | "event":"child_ready", | |
576 | ... | |
577 | "child_id":2, | |
578 | "pid":14708, # child PID | |
579 | "ready":"ready", # child ready state | |
580 | "t_rel":0.110605 # observed run-time of child process | |
581 | } | |
582 | ------------ | |
583 | + | |
584 | Note that the session-id of the child process is not available to | |
585 | the current/spawning process, so the child's PID is reported here as | |
586 | a hint for post-processing. (But it is only a hint because the child | |
587 | process may be a shell script which doesn't have a session-id.) | |
588 | + | |
589 | This event is generated after the child is started in the background | |
590 | and given a little time to boot up and start working. If the child | |
3188d3c0 | 591 | starts up normally while the parent is still waiting, the "ready" |
64bc7524 JH |
592 | field will have the value "ready". |
593 | If the child is too slow to start and the parent times out, the field | |
594 | will have the value "timeout". | |
595 | If the child starts but the parent is unable to probe it, the field | |
596 | will have the value "error". | |
597 | + | |
598 | After the parent process emits this event, it will release all of its | |
599 | handles to the child process and treat the child as a background | |
600 | daemon. So even if the child does eventually finish booting up, | |
601 | the parent will not emit an updated event. | |
602 | + | |
603 | Note that the `t_rel` field contains the observed run time in seconds | |
604 | when the parent released the child process into the background. | |
605 | The child is assumed to be a long-running daemon process and may | |
606 | outlive the parent process. So the parent's child event times should | |
607 | not be compared to the child's atexit times. | |
608 | ||
e544221d JH |
609 | `"exec"`:: |
610 | This event is generated before git attempts to `exec()` | |
611 | another command rather than starting a child process. | |
612 | + | |
613 | ------------ | |
614 | { | |
615 | "event":"exec", | |
616 | ... | |
617 | "exec_id":0, | |
618 | "exe":"git", | |
619 | "argv":["foo", "bar"] | |
620 | } | |
621 | ------------ | |
622 | + | |
623 | The "exec_id" field is a command-unique id and is only useful if the | |
624 | `exec()` fails and a corresponding exec_result event is generated. | |
625 | ||
626 | `"exec_result"`:: | |
627 | This event is generated if the `exec()` fails and control | |
628 | returns to the current git command. | |
629 | + | |
630 | ------------ | |
631 | { | |
632 | "event":"exec_result", | |
633 | ... | |
634 | "exec_id":0, | |
635 | "code":1 # error code (errno) from exec() | |
636 | } | |
637 | ------------ | |
638 | ||
639 | `"thread_start"`:: | |
640 | This event is generated when a thread is started. It is | |
5bbb9251 JH |
641 | generated from *within* the new thread's thread-proc (because |
642 | it needs to access data in the thread's thread-local storage). | |
e544221d JH |
643 | + |
644 | ------------ | |
645 | { | |
646 | "event":"thread_start", | |
647 | ... | |
648 | "thread":"th02:preload_thread" # thread name | |
649 | } | |
650 | ------------ | |
651 | ||
652 | `"thread_exit"`:: | |
653 | This event is generated when a thread exits. It is generated | |
5bbb9251 | 654 | from *within* the thread's thread-proc. |
e544221d JH |
655 | + |
656 | ------------ | |
657 | { | |
658 | "event":"thread_exit", | |
659 | ... | |
660 | "thread":"th02:preload_thread", # thread name | |
661 | "t_rel":0.007328 # thread elapsed time | |
662 | } | |
663 | ------------ | |
664 | ||
665 | `"def_param"`:: | |
3d3adaad JS |
666 | This event is generated to log a global parameter, such as a config |
667 | setting, command-line flag, or environment variable. | |
e544221d JH |
668 | + |
669 | ------------ | |
670 | { | |
671 | "event":"def_param", | |
672 | ... | |
35ae40ea | 673 | "scope":"global", |
e544221d JH |
674 | "param":"core.abbrev", |
675 | "value":"7" | |
676 | } | |
677 | ------------ | |
678 | ||
679 | `"def_repo"`:: | |
680 | This event defines a repo-id and associates it with the root | |
681 | of the worktree. | |
682 | + | |
683 | ------------ | |
684 | { | |
685 | "event":"def_repo", | |
686 | ... | |
687 | "repo":1, | |
688 | "worktree":"/Users/jeffhost/work/gfw" | |
689 | } | |
690 | ------------ | |
691 | + | |
692 | As stated earlier, the repo-id is currently always 1, so there will | |
693 | only be one def_repo event. Later, if in-proc submodules are | |
694 | supported, a def_repo event should be emitted for each submodule | |
695 | visited. | |
696 | ||
697 | `"region_enter"`:: | |
698 | This event is generated when entering a region. | |
699 | + | |
700 | ------------ | |
701 | { | |
702 | "event":"region_enter", | |
703 | ... | |
704 | "repo":1, # optional | |
705 | "nesting":1, # current region stack depth | |
706 | "category":"index", # optional | |
707 | "label":"do_read_index", # optional | |
708 | "msg":".git/index" # optional | |
709 | } | |
710 | ------------ | |
711 | + | |
712 | The `category` field may be used in a future enhancement to | |
713 | do category-based filtering. | |
714 | + | |
e4b75d6a | 715 | `GIT_TRACE2_EVENT_NESTING` or `trace2.eventNesting` can be used to |
e544221d JH |
716 | filter deeply nested regions and data events. It defaults to "2". |
717 | ||
718 | `"region_leave"`:: | |
719 | This event is generated when leaving a region. | |
720 | + | |
721 | ------------ | |
722 | { | |
723 | "event":"region_leave", | |
724 | ... | |
725 | "repo":1, # optional | |
726 | "t_rel":0.002876, # time spent in region in seconds | |
727 | "nesting":1, # region stack depth | |
728 | "category":"index", # optional | |
729 | "label":"do_read_index", # optional | |
730 | "msg":".git/index" # optional | |
731 | } | |
732 | ------------ | |
733 | ||
734 | `"data"`:: | |
735 | This event is generated to log a thread- and region-local | |
736 | key/value pair. | |
737 | + | |
738 | ------------ | |
739 | { | |
740 | "event":"data", | |
741 | ... | |
742 | "repo":1, # optional | |
743 | "t_abs":0.024107, # absolute elapsed time | |
744 | "t_rel":0.001031, # elapsed time in region/thread | |
745 | "nesting":2, # region stack depth | |
746 | "category":"index", | |
747 | "key":"read/cache_nr", | |
748 | "value":"3552" | |
749 | } | |
750 | ------------ | |
751 | + | |
752 | The "value" field may be an integer or a string. | |
753 | ||
754 | `"data-json"`:: | |
755 | This event is generated to log a pre-formatted JSON string | |
756 | containing structured data. | |
757 | + | |
758 | ------------ | |
759 | { | |
760 | "event":"data_json", | |
761 | ... | |
762 | "repo":1, # optional | |
763 | "t_abs":0.015905, | |
764 | "t_rel":0.015905, | |
765 | "nesting":1, | |
766 | "category":"process", | |
767 | "key":"windows/ancestry", | |
768 | "value":["bash.exe","bash.exe"] | |
769 | } | |
770 | ------------ | |
771 | ||
8ad57564 JH |
772 | `"th_timer"`:: |
773 | This event logs the amount of time that a stopwatch timer was | |
774 | running in the thread. This event is generated when a thread | |
775 | exits for timers that requested per-thread events. | |
776 | + | |
777 | ------------ | |
778 | { | |
779 | "event":"th_timer", | |
780 | ... | |
781 | "category":"my_category", | |
782 | "name":"my_timer", | |
783 | "intervals":5, # number of time it was started/stopped | |
784 | "t_total":0.052741, # total time in seconds it was running | |
785 | "t_min":0.010061, # shortest interval | |
786 | "t_max":0.011648 # longest interval | |
787 | } | |
788 | ------------ | |
789 | ||
790 | `"timer"`:: | |
791 | This event logs the amount of time that a stopwatch timer was | |
792 | running aggregated across all threads. This event is generated | |
793 | when the process exits. | |
794 | + | |
795 | ------------ | |
796 | { | |
797 | "event":"timer", | |
798 | ... | |
799 | "category":"my_category", | |
800 | "name":"my_timer", | |
801 | "intervals":5, # number of time it was started/stopped | |
802 | "t_total":0.052741, # total time in seconds it was running | |
803 | "t_min":0.010061, # shortest interval | |
804 | "t_max":0.011648 # longest interval | |
805 | } | |
806 | ------------ | |
807 | ||
81071626 JH |
808 | `"th_counter"`:: |
809 | This event logs the value of a counter variable in a thread. | |
810 | This event is generated when a thread exits for counters that | |
811 | requested per-thread events. | |
812 | + | |
813 | ------------ | |
814 | { | |
815 | "event":"th_counter", | |
816 | ... | |
817 | "category":"my_category", | |
818 | "name":"my_counter", | |
819 | "count":23 | |
820 | } | |
821 | ------------ | |
822 | ||
823 | `"counter"`:: | |
824 | This event logs the value of a counter variable across all threads. | |
825 | This event is generated when the process exits. The total value | |
826 | reported here is the sum across all threads. | |
827 | + | |
828 | ------------ | |
829 | { | |
830 | "event":"counter", | |
831 | ... | |
832 | "category":"my_category", | |
833 | "name":"my_counter", | |
834 | "count":23 | |
835 | } | |
836 | ------------ | |
837 | ||
838 | ||
e544221d JH |
839 | == Example Trace2 API Usage |
840 | ||
841 | Here is a hypothetical usage of the Trace2 API showing the intended | |
842 | usage (without worrying about the actual Git details). | |
843 | ||
844 | Initialization:: | |
845 | ||
846 | Initialization happens in `main()`. Behind the scenes, an | |
847 | `atexit` and `signal` handler are registered. | |
848 | + | |
849 | ---------------- | |
850 | int main(int argc, const char **argv) | |
851 | { | |
852 | int exit_code; | |
853 | ||
854 | trace2_initialize(); | |
855 | trace2_cmd_start(argv); | |
856 | ||
857 | exit_code = cmd_main(argc, argv); | |
858 | ||
859 | trace2_cmd_exit(exit_code); | |
860 | ||
861 | return exit_code; | |
862 | } | |
863 | ---------------- | |
864 | ||
865 | Command Details:: | |
866 | ||
867 | After the basics are established, additional command | |
868 | information can be sent to Trace2 as it is discovered. | |
869 | + | |
870 | ---------------- | |
871 | int cmd_checkout(int argc, const char **argv) | |
872 | { | |
873 | trace2_cmd_name("checkout"); | |
874 | trace2_cmd_mode("branch"); | |
875 | trace2_def_repo(the_repository); | |
876 | ||
877 | // emit "def_param" messages for "interesting" config settings. | |
878 | trace2_cmd_list_config(); | |
879 | ||
880 | if (do_something()) | |
881 | trace2_cmd_error("Path '%s': cannot do something", path); | |
882 | ||
883 | return 0; | |
884 | } | |
885 | ---------------- | |
886 | ||
887 | Child Processes:: | |
888 | ||
889 | Wrap code spawning child processes. | |
890 | + | |
891 | ---------------- | |
892 | void run_child(...) | |
893 | { | |
894 | int child_exit_code; | |
895 | struct child_process cmd = CHILD_PROCESS_INIT; | |
896 | ... | |
897 | cmd.trace2_child_class = "editor"; | |
898 | ||
899 | trace2_child_start(&cmd); | |
900 | child_exit_code = spawn_child_and_wait_for_it(); | |
901 | trace2_child_exit(&cmd, child_exit_code); | |
902 | } | |
903 | ---------------- | |
904 | + | |
905 | For example, the following fetch command spawned ssh, index-pack, | |
906 | rev-list, and gc. This example also shows that fetch took | |
907 | 5.199 seconds and of that 4.932 was in ssh. | |
908 | + | |
909 | ---------------- | |
e4b75d6a SG |
910 | $ export GIT_TRACE2_BRIEF=1 |
911 | $ export GIT_TRACE2=~/log.normal | |
e544221d JH |
912 | $ git fetch origin |
913 | ... | |
914 | ---------------- | |
915 | + | |
916 | ---------------- | |
917 | $ cat ~/log.normal | |
918 | version 2.20.1.vfs.1.1.47.g534dbe1ad1 | |
919 | start git fetch origin | |
920 | worktree /Users/jeffhost/work/gfw | |
921 | cmd_name fetch (fetch) | |
922 | child_start[0] ssh git@github.com ... | |
923 | child_start[1] git index-pack ... | |
924 | ... (Trace2 events from child processes omitted) | |
925 | child_exit[1] pid:14707 code:0 elapsed:0.076353 | |
926 | child_exit[0] pid:14706 code:0 elapsed:4.931869 | |
927 | child_start[2] git rev-list ... | |
928 | ... (Trace2 events from child process omitted) | |
929 | child_exit[2] pid:14708 code:0 elapsed:0.110605 | |
930 | child_start[3] git gc --auto | |
931 | ... (Trace2 events from child process omitted) | |
932 | child_exit[3] pid:14709 code:0 elapsed:0.006240 | |
933 | exit elapsed:5.198503 code:0 | |
934 | atexit elapsed:5.198541 code:0 | |
935 | ---------------- | |
936 | + | |
937 | When a git process is a (direct or indirect) child of another | |
938 | git process, it inherits Trace2 context information. This | |
939 | allows the child to print the command hierarchy. This example | |
940 | shows gc as child[3] of fetch. When the gc process reports | |
941 | its name as "gc", it also reports the hierarchy as "fetch/gc". | |
942 | (In this example, trace2 messages from the child process is | |
943 | indented for clarity.) | |
944 | + | |
945 | ---------------- | |
e4b75d6a SG |
946 | $ export GIT_TRACE2_BRIEF=1 |
947 | $ export GIT_TRACE2=~/log.normal | |
e544221d JH |
948 | $ git fetch origin |
949 | ... | |
950 | ---------------- | |
951 | + | |
952 | ---------------- | |
953 | $ cat ~/log.normal | |
954 | version 2.20.1.160.g5676107ecd.dirty | |
955 | start git fetch official | |
956 | worktree /Users/jeffhost/work/gfw | |
957 | cmd_name fetch (fetch) | |
958 | ... | |
959 | child_start[3] git gc --auto | |
960 | version 2.20.1.160.g5676107ecd.dirty | |
961 | start /Users/jeffhost/work/gfw/git gc --auto | |
962 | worktree /Users/jeffhost/work/gfw | |
963 | cmd_name gc (fetch/gc) | |
964 | exit elapsed:0.001959 code:0 | |
965 | atexit elapsed:0.001997 code:0 | |
966 | child_exit[3] pid:20303 code:0 elapsed:0.007564 | |
967 | exit elapsed:3.868938 code:0 | |
968 | atexit elapsed:3.868970 code:0 | |
969 | ---------------- | |
970 | ||
971 | Regions:: | |
972 | ||
3188d3c0 | 973 | Regions can be used to time an interesting section of code. |
e544221d JH |
974 | + |
975 | ---------------- | |
976 | void wt_status_collect(struct wt_status *s) | |
977 | { | |
978 | trace2_region_enter("status", "worktrees", s->repo); | |
979 | wt_status_collect_changes_worktree(s); | |
980 | trace2_region_leave("status", "worktrees", s->repo); | |
981 | ||
982 | trace2_region_enter("status", "index", s->repo); | |
983 | wt_status_collect_changes_index(s); | |
984 | trace2_region_leave("status", "index", s->repo); | |
985 | ||
986 | trace2_region_enter("status", "untracked", s->repo); | |
987 | wt_status_collect_untracked(s); | |
988 | trace2_region_leave("status", "untracked", s->repo); | |
989 | } | |
990 | ||
991 | void wt_status_print(struct wt_status *s) | |
992 | { | |
993 | trace2_region_enter("status", "print", s->repo); | |
994 | switch (s->status_format) { | |
995 | ... | |
996 | } | |
997 | trace2_region_leave("status", "print", s->repo); | |
998 | } | |
999 | ---------------- | |
1000 | + | |
1001 | In this example, scanning for untracked files ran from +0.012568 to | |
1002 | +0.027149 (since the process started) and took 0.014581 seconds. | |
1003 | + | |
1004 | ---------------- | |
e4b75d6a SG |
1005 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1006 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1007 | $ git status |
1008 | ... | |
1009 | ||
1010 | $ cat ~/log.perf | |
1011 | d0 | main | version | | | | | 2.20.1.160.g5676107ecd.dirty | |
39f43177 | 1012 | d0 | main | start | | 0.001173 | | | git status |
e544221d JH |
1013 | d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw |
1014 | d0 | main | cmd_name | | | | | status (status) | |
1015 | ... | |
1016 | d0 | main | region_enter | r1 | 0.010988 | | status | label:worktrees | |
1017 | d0 | main | region_leave | r1 | 0.011236 | 0.000248 | status | label:worktrees | |
1018 | d0 | main | region_enter | r1 | 0.011260 | | status | label:index | |
1019 | d0 | main | region_leave | r1 | 0.012542 | 0.001282 | status | label:index | |
1020 | d0 | main | region_enter | r1 | 0.012568 | | status | label:untracked | |
1021 | d0 | main | region_leave | r1 | 0.027149 | 0.014581 | status | label:untracked | |
1022 | d0 | main | region_enter | r1 | 0.027411 | | status | label:print | |
1023 | d0 | main | region_leave | r1 | 0.028741 | 0.001330 | status | label:print | |
1024 | d0 | main | exit | | 0.028778 | | | code:0 | |
1025 | d0 | main | atexit | | 0.028809 | | | code:0 | |
1026 | ---------------- | |
1027 | + | |
1028 | Regions may be nested. This causes messages to be indented in the | |
1029 | PERF target, for example. | |
031fd4b9 | 1030 | Elapsed times are relative to the start of the corresponding nesting |
e544221d JH |
1031 | level as expected. For example, if we add region message to: |
1032 | + | |
1033 | ---------------- | |
1034 | static enum path_treatment read_directory_recursive(struct dir_struct *dir, | |
1035 | struct index_state *istate, const char *base, int baselen, | |
1036 | struct untracked_cache_dir *untracked, int check_only, | |
1037 | int stop_at_first_file, const struct pathspec *pathspec) | |
1038 | { | |
1039 | enum path_treatment state, subdir_state, dir_state = path_none; | |
1040 | ||
1041 | trace2_region_enter_printf("dir", "read_recursive", NULL, "%.*s", baselen, base); | |
1042 | ... | |
1043 | trace2_region_leave_printf("dir", "read_recursive", NULL, "%.*s", baselen, base); | |
1044 | return dir_state; | |
1045 | } | |
1046 | ---------------- | |
1047 | + | |
1048 | We can further investigate the time spent scanning for untracked files. | |
1049 | + | |
1050 | ---------------- | |
e4b75d6a SG |
1051 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1052 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1053 | $ git status |
1054 | ... | |
1055 | $ cat ~/log.perf | |
1056 | d0 | main | version | | | | | 2.20.1.162.gb4ccea44db.dirty | |
39f43177 | 1057 | d0 | main | start | | 0.001173 | | | git status |
e544221d JH |
1058 | d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw |
1059 | d0 | main | cmd_name | | | | | status (status) | |
1060 | ... | |
1061 | d0 | main | region_enter | r1 | 0.015047 | | status | label:untracked | |
1062 | d0 | main | region_enter | | 0.015132 | | dir | ..label:read_recursive | |
1063 | d0 | main | region_enter | | 0.016341 | | dir | ....label:read_recursive vcs-svn/ | |
1064 | d0 | main | region_leave | | 0.016422 | 0.000081 | dir | ....label:read_recursive vcs-svn/ | |
1065 | d0 | main | region_enter | | 0.016446 | | dir | ....label:read_recursive xdiff/ | |
1066 | d0 | main | region_leave | | 0.016522 | 0.000076 | dir | ....label:read_recursive xdiff/ | |
1067 | d0 | main | region_enter | | 0.016612 | | dir | ....label:read_recursive git-gui/ | |
1068 | d0 | main | region_enter | | 0.016698 | | dir | ......label:read_recursive git-gui/po/ | |
1069 | d0 | main | region_enter | | 0.016810 | | dir | ........label:read_recursive git-gui/po/glossary/ | |
1070 | d0 | main | region_leave | | 0.016863 | 0.000053 | dir | ........label:read_recursive git-gui/po/glossary/ | |
1071 | ... | |
1072 | d0 | main | region_enter | | 0.031876 | | dir | ....label:read_recursive builtin/ | |
1073 | d0 | main | region_leave | | 0.032270 | 0.000394 | dir | ....label:read_recursive builtin/ | |
1074 | d0 | main | region_leave | | 0.032414 | 0.017282 | dir | ..label:read_recursive | |
1075 | d0 | main | region_leave | r1 | 0.032454 | 0.017407 | status | label:untracked | |
1076 | ... | |
1077 | d0 | main | exit | | 0.034279 | | | code:0 | |
1078 | d0 | main | atexit | | 0.034322 | | | code:0 | |
1079 | ---------------- | |
1080 | + | |
1081 | Trace2 regions are similar to the existing trace_performance_enter() | |
1082 | and trace_performance_leave() routines, but are thread safe and | |
1083 | maintain per-thread stacks of timers. | |
1084 | ||
1085 | Data Messages:: | |
1086 | ||
1087 | Data messages added to a region. | |
1088 | + | |
1089 | ---------------- | |
1090 | int read_index_from(struct index_state *istate, const char *path, | |
1091 | const char *gitdir) | |
1092 | { | |
1093 | trace2_region_enter_printf("index", "do_read_index", the_repository, "%s", path); | |
1094 | ||
1095 | ... | |
1096 | ||
1097 | trace2_data_intmax("index", the_repository, "read/version", istate->version); | |
1098 | trace2_data_intmax("index", the_repository, "read/cache_nr", istate->cache_nr); | |
1099 | ||
1100 | trace2_region_leave_printf("index", "do_read_index", the_repository, "%s", path); | |
1101 | } | |
1102 | ---------------- | |
1103 | + | |
1104 | This example shows that the index contained 3552 entries. | |
1105 | + | |
1106 | ---------------- | |
e4b75d6a SG |
1107 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1108 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1109 | $ git status |
1110 | ... | |
1111 | $ cat ~/log.perf | |
1112 | d0 | main | version | | | | | 2.20.1.156.gf9916ae094.dirty | |
39f43177 | 1113 | d0 | main | start | | 0.001173 | | | git status |
e544221d JH |
1114 | d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw |
1115 | d0 | main | cmd_name | | | | | status (status) | |
1116 | d0 | main | region_enter | r1 | 0.001791 | | index | label:do_read_index .git/index | |
1117 | d0 | main | data | r1 | 0.002494 | 0.000703 | index | ..read/version:2 | |
1118 | d0 | main | data | r1 | 0.002520 | 0.000729 | index | ..read/cache_nr:3552 | |
1119 | d0 | main | region_leave | r1 | 0.002539 | 0.000748 | index | label:do_read_index .git/index | |
1120 | ... | |
1121 | ---------------- | |
1122 | ||
1123 | Thread Events:: | |
1124 | ||
1125 | Thread messages added to a thread-proc. | |
1126 | + | |
3188d3c0 | 1127 | For example, the multi-threaded preload-index code can be |
e544221d | 1128 | instrumented with a region around the thread pool and then |
3188d3c0 | 1129 | per-thread start and exit events within the thread-proc. |
e544221d JH |
1130 | + |
1131 | ---------------- | |
1132 | static void *preload_thread(void *_data) | |
1133 | { | |
1134 | // start the per-thread clock and emit a message. | |
1135 | trace2_thread_start("preload_thread"); | |
1136 | ||
1137 | // report which chunk of the array this thread was assigned. | |
1138 | trace2_data_intmax("index", the_repository, "offset", p->offset); | |
1139 | trace2_data_intmax("index", the_repository, "count", nr); | |
1140 | ||
1141 | do { | |
1142 | ... | |
1143 | } while (--nr > 0); | |
1144 | ... | |
1145 | ||
1146 | // report elapsed time taken by this thread. | |
1147 | trace2_thread_exit(); | |
1148 | return NULL; | |
1149 | } | |
1150 | ||
1151 | void preload_index(struct index_state *index, | |
1152 | const struct pathspec *pathspec, | |
1153 | unsigned int refresh_flags) | |
1154 | { | |
1155 | trace2_region_enter("index", "preload", the_repository); | |
1156 | ||
1157 | for (i = 0; i < threads; i++) { | |
1158 | ... /* create thread */ | |
1159 | } | |
1160 | ||
1161 | for (i = 0; i < threads; i++) { | |
1162 | ... /* join thread */ | |
1163 | } | |
1164 | ||
1165 | trace2_region_leave("index", "preload", the_repository); | |
1166 | } | |
1167 | ---------------- | |
1168 | + | |
1169 | In this example preload_index() was executed by the `main` thread | |
1170 | and started the `preload` region. Seven threads, named | |
1171 | `th01:preload_thread` through `th07:preload_thread`, were started. | |
1172 | Events from each thread are atomically appended to the shared target | |
1173 | stream as they occur so they may appear in random order with respect | |
1174 | other threads. Finally, the main thread waits for the threads to | |
1175 | finish and leaves the region. | |
1176 | + | |
1177 | Data events are tagged with the active thread name. They are used | |
1178 | to report the per-thread parameters. | |
1179 | + | |
1180 | ---------------- | |
e4b75d6a SG |
1181 | $ export GIT_TRACE2_PERF_BRIEF=1 |
1182 | $ export GIT_TRACE2_PERF=~/log.perf | |
e544221d JH |
1183 | $ git status |
1184 | ... | |
1185 | $ cat ~/log.perf | |
1186 | ... | |
1187 | d0 | main | region_enter | r1 | 0.002595 | | index | label:preload | |
1188 | d0 | th01:preload_thread | thread_start | | 0.002699 | | | | |
1189 | d0 | th02:preload_thread | thread_start | | 0.002721 | | | | |
1190 | d0 | th01:preload_thread | data | r1 | 0.002736 | 0.000037 | index | offset:0 | |
1191 | d0 | th02:preload_thread | data | r1 | 0.002751 | 0.000030 | index | offset:2032 | |
1192 | d0 | th03:preload_thread | thread_start | | 0.002711 | | | | |
1193 | d0 | th06:preload_thread | thread_start | | 0.002739 | | | | |
1194 | d0 | th01:preload_thread | data | r1 | 0.002766 | 0.000067 | index | count:508 | |
1195 | d0 | th06:preload_thread | data | r1 | 0.002856 | 0.000117 | index | offset:2540 | |
1196 | d0 | th03:preload_thread | data | r1 | 0.002824 | 0.000113 | index | offset:1016 | |
1197 | d0 | th04:preload_thread | thread_start | | 0.002710 | | | | |
1198 | d0 | th02:preload_thread | data | r1 | 0.002779 | 0.000058 | index | count:508 | |
1199 | d0 | th06:preload_thread | data | r1 | 0.002966 | 0.000227 | index | count:508 | |
1200 | d0 | th07:preload_thread | thread_start | | 0.002741 | | | | |
1201 | d0 | th07:preload_thread | data | r1 | 0.003017 | 0.000276 | index | offset:3048 | |
1202 | d0 | th05:preload_thread | thread_start | | 0.002712 | | | | |
1203 | d0 | th05:preload_thread | data | r1 | 0.003067 | 0.000355 | index | offset:1524 | |
1204 | d0 | th05:preload_thread | data | r1 | 0.003090 | 0.000378 | index | count:508 | |
1205 | d0 | th07:preload_thread | data | r1 | 0.003037 | 0.000296 | index | count:504 | |
1206 | d0 | th03:preload_thread | data | r1 | 0.002971 | 0.000260 | index | count:508 | |
1207 | d0 | th04:preload_thread | data | r1 | 0.002983 | 0.000273 | index | offset:508 | |
1208 | d0 | th04:preload_thread | data | r1 | 0.007311 | 0.004601 | index | count:508 | |
1209 | d0 | th05:preload_thread | thread_exit | | 0.008781 | 0.006069 | | | |
1210 | d0 | th01:preload_thread | thread_exit | | 0.009561 | 0.006862 | | | |
1211 | d0 | th03:preload_thread | thread_exit | | 0.009742 | 0.007031 | | | |
1212 | d0 | th06:preload_thread | thread_exit | | 0.009820 | 0.007081 | | | |
1213 | d0 | th02:preload_thread | thread_exit | | 0.010274 | 0.007553 | | | |
1214 | d0 | th07:preload_thread | thread_exit | | 0.010477 | 0.007736 | | | |
1215 | d0 | th04:preload_thread | thread_exit | | 0.011657 | 0.008947 | | | |
1216 | d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload | |
1217 | ... | |
1218 | d0 | main | exit | | 0.029996 | | | code:0 | |
1219 | d0 | main | atexit | | 0.030027 | | | code:0 | |
1220 | ---------------- | |
1221 | + | |
1222 | In this example, the preload region took 0.009122 seconds. The 7 threads | |
1223 | took between 0.006069 and 0.008947 seconds to work on their portion of | |
1224 | the index. Thread "th01" worked on 508 items at offset 0. Thread "th02" | |
031fd4b9 | 1225 | worked on 508 items at offset 2032. Thread "th04" worked on 508 items |
e544221d JH |
1226 | at offset 508. |
1227 | + | |
1228 | This example also shows that thread names are assigned in a racy manner | |
5bbb9251 | 1229 | as each thread starts. |
e544221d | 1230 | |
050d0dc2 TL |
1231 | Config (def param) Events:: |
1232 | ||
1233 | Dump "interesting" config values to trace2 log. | |
1234 | + | |
1235 | We can optionally emit configuration events, see | |
1236 | `trace2.configparams` in linkgit:git-config[1] for how to enable | |
1237 | it. | |
1238 | + | |
1239 | ---------------- | |
35ae40ea TL |
1240 | $ git config --system color.ui never |
1241 | $ git config --global color.ui always | |
1242 | $ git config --local color.ui auto | |
1243 | $ git config --list --show-scope | grep 'color.ui' | |
1244 | system color.ui=never | |
1245 | global color.ui=always | |
1246 | local color.ui=auto | |
050d0dc2 TL |
1247 | ---------------- |
1248 | + | |
1249 | Then, mark the config `color.ui` as "interesting" config with | |
1250 | `GIT_TRACE2_CONFIG_PARAMS`: | |
1251 | + | |
1252 | ---------------- | |
1253 | $ export GIT_TRACE2_PERF_BRIEF=1 | |
1254 | $ export GIT_TRACE2_PERF=~/log.perf | |
1255 | $ export GIT_TRACE2_CONFIG_PARAMS=color.ui | |
1256 | $ git version | |
1257 | ... | |
1258 | $ cat ~/log.perf | |
1259 | d0 | main | version | | | | | ... | |
1260 | d0 | main | start | | 0.001642 | | | /usr/local/bin/git version | |
1261 | d0 | main | cmd_name | | | | | version (version) | |
35ae40ea TL |
1262 | d0 | main | def_param | | | | scope:system | color.ui:never |
1263 | d0 | main | def_param | | | | scope:global | color.ui:always | |
1264 | d0 | main | def_param | | | | scope:local | color.ui:auto | |
050d0dc2 TL |
1265 | d0 | main | data | r0 | 0.002100 | 0.002100 | fsync | fsync/writeout-only:0 |
1266 | d0 | main | data | r0 | 0.002126 | 0.002126 | fsync | fsync/hardware-flush:0 | |
35ae40ea TL |
1267 | d0 | main | exit | | 0.000470 | | | code:0 |
1268 | d0 | main | atexit | | 0.000477 | | | code:0 | |
050d0dc2 | 1269 | ---------------- |
8ad57564 JH |
1270 | |
1271 | Stopwatch Timer Events:: | |
1272 | ||
1273 | Measure the time spent in a function call or span of code | |
1274 | that might be called from many places within the code | |
1275 | throughout the life of the process. | |
1276 | + | |
1277 | ---------------- | |
1278 | static void expensive_function(void) | |
1279 | { | |
1280 | trace2_timer_start(TRACE2_TIMER_ID_TEST1); | |
1281 | ... | |
1282 | sleep_millisec(1000); // Do something expensive | |
1283 | ... | |
1284 | trace2_timer_stop(TRACE2_TIMER_ID_TEST1); | |
1285 | } | |
1286 | ||
1287 | static int ut_100timer(int argc, const char **argv) | |
1288 | { | |
1289 | ... | |
1290 | ||
1291 | expensive_function(); | |
1292 | ||
1293 | // Do something else 1... | |
1294 | ||
1295 | expensive_function(); | |
1296 | ||
1297 | // Do something else 2... | |
1298 | ||
1299 | expensive_function(); | |
1300 | ||
1301 | return 0; | |
1302 | } | |
1303 | ---------------- | |
1304 | + | |
1305 | In this example, we measure the total time spent in | |
1306 | `expensive_function()` regardless of when it is called | |
1307 | in the overall flow of the program. | |
1308 | + | |
1309 | ---------------- | |
1310 | $ export GIT_TRACE2_PERF_BRIEF=1 | |
1311 | $ export GIT_TRACE2_PERF=~/log.perf | |
1312 | $ t/helper/test-tool trace2 100timer 3 1000 | |
1313 | ... | |
1314 | $ cat ~/log.perf | |
1315 | d0 | main | version | | | | | ... | |
1316 | d0 | main | start | | 0.001453 | | | t/helper/test-tool trace2 100timer 3 1000 | |
1317 | d0 | main | cmd_name | | | | | trace2 (trace2) | |
1318 | d0 | main | exit | | 3.003667 | | | code:0 | |
1319 | d0 | main | timer | | | | test | name:test1 intervals:3 total:3.001686 min:1.000254 max:1.000929 | |
1320 | d0 | main | atexit | | 3.003796 | | | code:0 | |
1321 | ---------------- | |
1322 | ||
1323 | ||
e544221d JH |
1324 | == Future Work |
1325 | ||
1326 | === Relationship to the Existing Trace Api (api-trace.txt) | |
1327 | ||
1328 | There are a few issues to resolve before we can completely | |
1329 | switch to Trace2. | |
1330 | ||
1c538b95 | 1331 | * Updating existing tests that assume `GIT_TRACE` format messages. |
e544221d | 1332 | |
1c538b95 | 1333 | * How to best handle custom `GIT_TRACE_<key>` messages? |
e544221d | 1334 | |
1c538b95 | 1335 | ** The `GIT_TRACE_<key>` mechanism allows each <key> to write to a |
e544221d JH |
1336 | different file (in addition to just stderr). |
1337 | ||
1338 | ** Do we want to maintain that ability or simply write to the existing | |
1339 | Trace2 targets (and convert <key> to a "category"). |