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Diffstat (limited to 'Documentation/technical/api-trace2.txt')
| -rw-r--r-- | Documentation/technical/api-trace2.txt | 209 |
1 files changed, 119 insertions, 90 deletions
diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt index 2de565fa3d..23c3cc7a37 100644 --- a/Documentation/technical/api-trace2.txt +++ b/Documentation/technical/api-trace2.txt @@ -22,21 +22,41 @@ Targets are defined using a VTable allowing easy extension to other formats in the future. This might be used to define a binary format, for example. +Trace2 is controlled using `trace2.*` config values in the system and +global config files and `GIT_TRACE2*` environment variables. Trace2 does +not read from repo local or worktree config files or respect `-c` +command line config settings. + == Trace2 Targets Trace2 defines the following set of Trace2 Targets. Format details are given in a later section. -`GIT_TR2` (NORMAL):: +=== The Normal Format Target + +The normal format target is a tradition printf format and similar +to GIT_TRACE format. This format is enabled with the `GIT_TR` +environment variable or the `trace2.normalTarget` system or global +config setting. + +For example - a simple printf format like GIT_TRACE. -+ ------------ -$ export GIT_TR2=~/log.normal +$ export GIT_TRACE2=~/log.normal $ git version git version 2.20.1.155.g426c96fcdb ------------ -+ + +or + +------------ +$ git config --global trace2.normalTarget ~/log.normal +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +yields + ------------ $ cat ~/log.normal 12:28:42.620009 common-main.c:38 version 2.20.1.155.g426c96fcdb @@ -46,76 +66,86 @@ $ cat ~/log.normal 12:28:42.621250 trace2/tr2_tgt_normal.c:124 atexit elapsed:0.001265 code:0 ------------ -`GIT_TR2_PERF` (PERF):: +=== The Performance Format Target + +The performance format target (PERF) is a column-based format to +replace GIT_TRACE_PERFORMANCE and is suitable for development and +testing, possibly to complement tools like gprof. This format is +enabled with the `GIT_TRACE2_PERF` environment variable or the +`trace2.perfTarget` system or global config setting. + +For example - a column-based format to replace GIT_TRACE_PERFORMANCE suitable for - development and testing, possibly to complement tools like gprof. -+ ------------ -$ export GIT_TR2_PERF=~/log.perf +$ export GIT_TRACE2_PERF=~/log.perf $ git version git version 2.20.1.155.g426c96fcdb ------------ -+ + +or + +------------ +$ git config --global trace2.perfTarget ~/log.perf +$ git version +git version 2.20.1.155.g426c96fcdb +------------ + +yields + ------------ $ cat ~/log.perf 12:28:42.620675 common-main.c:38 | d0 | main | version | | | | | 2.20.1.155.g426c96fcdb -12:28:42.621001 common-main.c:39 | d0 | main | start | | | | | git version +12:28:42.621001 common-main.c:39 | d0 | main | start | | 0.001173 | | | git version 12:28:42.621111 git.c:432 | d0 | main | cmd_name | | | | | version (version) 12:28:42.621225 git.c:662 | d0 | main | exit | | 0.001227 | | | code:0 12:28:42.621259 trace2/tr2_tgt_perf.c:211 | d0 | main | atexit | | 0.001265 | | | code:0 ------------ -`GIT_TR2_EVENT` (EVENT):: +=== The Event Format Target + +The event format target is a JSON-based format of event data suitable +for telemetry analysis. This format is enabled with the `GIT_TRACE2_EVENT` +environment variable or the `trace2.eventTarget` system or global config +setting. + +For example - a JSON-based format of event data suitable for telemetry analysis. -+ ------------ -$ export GIT_TR2_EVENT=~/log.event +$ export GIT_TRACE2_EVENT=~/log.event $ git version git version 2.20.1.155.g426c96fcdb ------------ -+ ------------- -$ cat ~/log.event -{"event":"version","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.620713","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"} -{"event":"start","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621027","file":"common-main.c","line":39,"argv":["git","version"]} -{"event":"cmd_name","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621122","file":"git.c","line":432,"name":"version","hierarchy":"version"} -{"event":"exit","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621236","file":"git.c","line":662,"t_abs":0.001227,"code":0} -{"event":"atexit","sid":"1547659722619736-11614","thread":"main","time":"2019-01-16 17:28:42.621268","file":"trace2/tr2_tgt_event.c","line":163,"t_abs":0.001265,"code":0} ------------- -== Enabling a Target +or -A Trace2 Target is enabled when the corresponding environment variable -(`GIT_TR2`, `GIT_TR2_PERF`, or `GIT_TR2_EVENT`) is set. The following -values are recognized. - -`0`:: -`false`:: - - Disables the target. - -`1`:: -`true`:: - - Enables the target and writes stream to `STDERR`. +------------ +$ git config --global trace2.eventTarget ~/log.event +$ git version +git version 2.20.1.155.g426c96fcdb +------------ -`[2-9]`:: +yields - Enables the target and writes to the already opened file descriptor. +------------ +$ cat ~/log.event +{"event":"version","sid":"sid":"20190408T191610.507018Z-H9b68c35f-P000059a8","thread":"main","time":"2019-01-16T17:28:42.620713Z","file":"common-main.c","line":38,"evt":"1","exe":"2.20.1.155.g426c96fcdb"} +{"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"]} +{"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"} +{"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} +{"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} +------------ -`<absolute-pathname>`:: +=== Enabling a Target - Enables the target, opens and writes to the file in append mode. +To enable a target, set the corresponding environment variable or +system or global config value to one of the following: -`af_unix:[<socket_type>:]<absolute-pathname>`:: +include::../trace2-target-values.txt[] - Enables the target, opens and writes to a Unix Domain Socket - (on platforms that support them). -+ -Socket type can be either `stream` or `dgram`. If the socket type is -omitted, Git will try both. +If the target already exists and is a directory, the traces will be +written to files (one per process) underneath the given directory. They +will be named according to the last component of the SID (optionally +followed by a counter to avoid filename collisions). == Trace2 API @@ -160,17 +190,23 @@ purposes. These are concerned with the lifetime of the overall git process. +`void trace2_initialize_clock()`:: + + Initialize the Trace2 start clock and nothing else. This should + be called at the very top of main() to capture the process start + time and reduce startup order dependencies. + `void trace2_initialize()`:: Determines if any Trace2 Targets should be enabled and - initializes the Trace2 facility. This includes starting the - elapsed time clocks and thread local storage (TLS). + initializes the Trace2 facility. This includes setting up the + Trace2 thread local storage (TLS). + This function emits a "version" message containing the version of git and the Trace2 protocol. + This function should be called from `main()` as early as possible in -the life of the process. +the life of the process after essential process initialization. `int trace2_is_enabled()`:: @@ -237,15 +273,16 @@ significantly affects program performance or behavior, such as Emits a "def_param" messages for "important" configuration settings. + -The environment variable `GIT_TR2_CONFIG_PARAMS` can be set to a +The environment variable `GIT_TRACE2_CONFIG_PARAMS` or the `trace2.configParams` +config value can be set to a list of patterns of important configuration settings, for example: `core.*,remote.*.url`. This function will iterate over all config settings and emit a "def_param" message for each match. `void trace2_cmd_set_config(const char *key, const char *value)`:: - Emits a "def_param" message for a specific configuration - setting IFF it matches the `GIT_TR2_CONFIG_PARAMS` pattern. + Emits a "def_param" message for a new or updated key/value + pair IF `key` is considered important. + This is used to hook into `git_config_set()` and catch any configuration changes and update a value previously reported by @@ -412,9 +449,6 @@ recursive tree walk. === NORMAL Format -NORMAL format is enabled when the `GIT_TR2` environment variable is -set. - Events are written as lines of the form: ------------ @@ -431,8 +465,8 @@ Events are written as lines of the form: Note that this may contain embedded LF or CRLF characters that are not escaped, so the event may spill across multiple lines. -If `GIT_TR2_BRIEF` is true, the `time`, `filename`, and `line` fields -are omitted. +If `GIT_TRACE2_BRIEF` or `trace2.normalBrief` is true, the `time`, `filename`, +and `line` fields are omitted. This target is intended to be more of a summary (like GIT_TRACE) and less detailed than the other targets. It ignores thread, region, and @@ -440,9 +474,6 @@ data messages, for example. === PERF Format -PERF format is enabled when the `GIT_TR2_PERF` environment variable -is set. - Events are written as lines of the form: ------------ @@ -502,8 +533,8 @@ This field is in anticipation of in-proc submodules in the future. 15:33:33.532712 wt-status.c:2331 | d0 | main | region_leave | r1 | 0.127568 | 0.001504 | status | label:print ------------ -If `GIT_TR2_PERF_BRIEF` is true, the `time`, `file`, and `line` -fields are omitted. +If `GIT_TRACE2_PERF_BRIEF` or `trace2.perfBrief` is true, the `time`, `file`, +and `line` fields are omitted. ------------ d0 | main | region_leave | r1 | 0.011717 | 0.009122 | index | label:preload @@ -514,9 +545,6 @@ during development and is quite noisy. === EVENT Format -EVENT format is enabled when the `GIT_TR2_EVENT` environment -variable is set. - Each event is a JSON-object containing multiple key/value pairs written as a single line and followed by a LF. @@ -534,11 +562,11 @@ The following key/value pairs are common to all events: ------------ { "event":"version", - "sid":"1547659722619736-11614", + "sid":"20190408T191827.272759Z-H9b68c35f-P00003510", "thread":"main", - "time":"2019-01-16 17:28:42.620713", + "time":"2019-04-08T19:18:27.282761Z", "file":"common-main.c", - "line":38, + "line":42, ... } ------------ @@ -570,9 +598,9 @@ The following key/value pairs are common to all events: `"repo":<repo-id>`:: when present, is the integer repo-id as described previously. -If `GIT_TR2_EVENT_BRIEF` is true, the `file` and `line` fields are omitted -from all events and the `time` field is only present on the "start" and -"atexit" events. +If `GIT_TRACE2_EVENT_BRIEF` or `trace2.eventBrief` is true, the `file` +and `line` fields are omitted from all events and the `time` field is +only present on the "start" and "atexit" events. ==== Event-Specific Key/Value Pairs @@ -595,6 +623,7 @@ from all events and the `time` field is only present on the "start" and { "event":"start", ... + "t_abs":0.001227, # elapsed time in seconds "argv":["git","version"] } ------------ @@ -882,7 +911,7 @@ visited. The `category` field may be used in a future enhancement to do category-based filtering. + -The `GIT_TR2_EVENT_NESTING` environment variable can be used to +`GIT_TRACE2_EVENT_NESTING` or `trace2.eventNesting` can be used to filter deeply nested regions and data events. It defaults to "2". `"region_leave"`:: @@ -1010,8 +1039,8 @@ rev-list, and gc. This example also shows that fetch took 5.199 seconds and of that 4.932 was in ssh. + ---------------- -$ export GIT_TR2_BRIEF=1 -$ export GIT_TR2=~/log.normal +$ export GIT_TRACE2_BRIEF=1 +$ export GIT_TRACE2=~/log.normal $ git fetch origin ... ---------------- @@ -1046,8 +1075,8 @@ its name as "gc", it also reports the hierarchy as "fetch/gc". indented for clarity.) + ---------------- -$ export GIT_TR2_BRIEF=1 -$ export GIT_TR2=~/log.normal +$ export GIT_TRACE2_BRIEF=1 +$ export GIT_TRACE2=~/log.normal $ git fetch origin ... ---------------- @@ -1105,14 +1134,14 @@ In this example, scanning for untracked files ran from +0.012568 to +0.027149 (since the process started) and took 0.014581 seconds. + ---------------- -$ export GIT_TR2_PERF_BRIEF=1 -$ export GIT_TR2_PERF=~/log.perf +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf $ git status ... $ cat ~/log.perf d0 | main | version | | | | | 2.20.1.160.g5676107ecd.dirty -d0 | main | start | | | | | git status +d0 | main | start | | 0.001173 | | | git status d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw d0 | main | cmd_name | | | | | status (status) ... @@ -1151,13 +1180,13 @@ static enum path_treatment read_directory_recursive(struct dir_struct *dir, We can further investigate the time spent scanning for untracked files. + ---------------- -$ export GIT_TR2_PERF_BRIEF=1 -$ export GIT_TR2_PERF=~/log.perf +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf $ git status ... $ cat ~/log.perf d0 | main | version | | | | | 2.20.1.162.gb4ccea44db.dirty -d0 | main | start | | | | | git status +d0 | main | start | | 0.001173 | | | git status d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw d0 | main | cmd_name | | | | | status (status) ... @@ -1207,13 +1236,13 @@ int read_index_from(struct index_state *istate, const char *path, This example shows that the index contained 3552 entries. + ---------------- -$ export GIT_TR2_PERF_BRIEF=1 -$ export GIT_TR2_PERF=~/log.perf +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf $ git status ... $ cat ~/log.perf d0 | main | version | | | | | 2.20.1.156.gf9916ae094.dirty -d0 | main | start | | | | | git status +d0 | main | start | | 0.001173 | | | git status d0 | main | def_repo | r1 | | | | worktree:/Users/jeffhost/work/gfw d0 | main | cmd_name | | | | | status (status) d0 | main | region_enter | r1 | 0.001791 | | index | label:do_read_index .git/index @@ -1281,8 +1310,8 @@ Data events are tagged with the active thread name. They are used to report the per-thread parameters. + ---------------- -$ export GIT_TR2_PERF_BRIEF=1 -$ export GIT_TR2_PERF=~/log.perf +$ export GIT_TRACE2_PERF_BRIEF=1 +$ export GIT_TRACE2_PERF=~/log.perf $ git status ... $ cat ~/log.perf |