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-rw-r--r--technical/api-trace2.txt40
1 files changed, 40 insertions, 0 deletions
diff --git a/technical/api-trace2.txt b/technical/api-trace2.txt
index 77a150b30..2afa28bb5 100644
--- a/technical/api-trace2.txt
+++ b/technical/api-trace2.txt
@@ -717,6 +717,7 @@ The "exec_id" field is a command-unique id and is only useful if the
{
"event":"def_param",
...
+ "scope":"global",
"param":"core.abbrev",
"value":"7"
}
@@ -1207,6 +1208,45 @@ at offset 508.
This example also shows that thread names are assigned in a racy manner
as each thread starts and allocates TLS storage.
+Config (def param) Events::
+
+ Dump "interesting" config values to trace2 log.
++
+We can optionally emit configuration events, see
+`trace2.configparams` in linkgit:git-config[1] for how to enable
+it.
++
+----------------
+$ git config --system color.ui never
+$ git config --global color.ui always
+$ git config --local color.ui auto
+$ git config --list --show-scope | grep 'color.ui'
+system color.ui=never
+global color.ui=always
+local color.ui=auto
+----------------
++
+Then, mark the config `color.ui` as "interesting" config with
+`GIT_TRACE2_CONFIG_PARAMS`:
++
+----------------
+$ export GIT_TRACE2_PERF_BRIEF=1
+$ export GIT_TRACE2_PERF=~/log.perf
+$ export GIT_TRACE2_CONFIG_PARAMS=color.ui
+$ git version
+...
+$ cat ~/log.perf
+d0 | main | version | | | | | ...
+d0 | main | start | | 0.001642 | | | /usr/local/bin/git version
+d0 | main | cmd_name | | | | | version (version)
+d0 | main | def_param | | | | scope:system | color.ui:never
+d0 | main | def_param | | | | scope:global | color.ui:always
+d0 | main | def_param | | | | scope:local | color.ui:auto
+d0 | main | data | r0 | 0.002100 | 0.002100 | fsync | fsync/writeout-only:0
+d0 | main | data | r0 | 0.002126 | 0.002126 | fsync | fsync/hardware-flush:0
+d0 | main | exit | | 0.000470 | | | code:0
+d0 | main | atexit | | 0.000477 | | | code:0
+----------------
== Future Work
=== Relationship to the Existing Trace Api (api-trace.txt)