trace2: create new combined trace facility

Create a new unified tracing facility for git.  The eventual intent is to
replace the current trace_printf* and trace_performance* routines with a
unified set of git_trace2* routines.

In addition to the usual printf-style API, trace2 provides higer-level
event verbs with fixed-fields allowing structured data to be written.
This makes post-processing and analysis easier for external tools.

Trace2 defines 3 output targets.  These are set using the environment
variables "GIT_TR2", "GIT_TR2_PERF", and "GIT_TR2_EVENT".  These may be
set to "1" or to an absolute pathname (just like the current GIT_TRACE).

* GIT_TR2 is intended to be a replacement for GIT_TRACE and logs command
  summary data.

* GIT_TR2_PERF is intended as a replacement for GIT_TRACE_PERFORMANCE.
  It extends the output with columns for the command process, thread,
  repo, absolute and relative elapsed times.  It reports events for
  child process start/stop, thread start/stop, and per-thread function
  nesting.

* GIT_TR2_EVENT is a new structured format. It writes event data as a
  series of JSON records.

Calls to trace2 functions log to any of the 3 output targets enabled
without the need to call different trace_printf* or trace_performance*
routines.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 12 insertions, 1 deletions

diff --git a/run-command.h b/run-command.h
index 68f5369fc2..a6950691c0 100644
--- a/run-command.h
+++ b/run-command.h
@@ -10,6 +10,12 @@ struct child_process {
 	struct argv_array args;
 	struct argv_array env_array;
 	pid_t pid;
+
+	int trace2_child_id;
+	uint64_t trace2_child_us_start;
+	const char *trace2_child_class;
+	const char *trace2_hook_name;
+
 	/*
 	 * Using .in, .out, .err:
 	 * - Specify 0 for no redirections (child inherits stdin, stdout,
@@ -73,12 +79,14 @@ extern int run_hook_ve(const char *const *env, const char *name, va_list args);
 #define RUN_USING_SHELL 16
 #define RUN_CLEAN_ON_EXIT 32
 int run_command_v_opt(const char **argv, int opt);
-
+int run_command_v_opt_tr2(const char **argv, int opt, const char *tr2_class);
 /*
  * env (the environment) is to be formatted like environ: "VAR=VALUE".
  * To unset an environment variable use just "VAR".
  */
 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env);
+int run_command_v_opt_cd_env_tr2(const char **argv, int opt, const char *dir,
+				 const char *const *env, const char *tr2_class);
 
 /**
  * Execute the given command, sending "in" to its stdin, and capturing its
@@ -220,5 +228,8 @@ int run_processes_parallel(int n,
 			   start_failure_fn,
 			   task_finished_fn,
 			   void *pp_cb);
+int run_processes_parallel_tr2(int n, get_next_task_fn, start_failure_fn,
+			       task_finished_fn, void *pp_cb,
+			       const char *tr2_category, const char *tr2_label);
 
 #endif