From a089724958a99924d9ec7ff60a6aea63d03448f2 Mon Sep 17 00:00:00 2001 From: Jeff Hostetler Date: Mon, 15 Apr 2019 13:39:43 -0700 Subject: trace2: refactor setting process starting time Create trace2_initialize_clock() and call from main() to capture process start time in isolation and before other sub-systems are ready. Signed-off-by: Jeff Hostetler Signed-off-by: Junio C Hamano diff --git a/Documentation/technical/api-trace2.txt b/Documentation/technical/api-trace2.txt index 2de565f..f37fccf 100644 --- a/Documentation/technical/api-trace2.txt +++ b/Documentation/technical/api-trace2.txt @@ -160,17 +160,23 @@ 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()`:: diff --git a/common-main.c b/common-main.c index d484aec..6137af0 100644 --- a/common-main.c +++ b/common-main.c @@ -27,6 +27,8 @@ int main(int argc, const char **argv) { int result; + trace2_initialize_clock(); + /* * Always open file descriptors 0/1/2 to avoid clobbering files * in die(). It also avoids messing up when the pipes are dup'ed diff --git a/compat/mingw.c b/compat/mingw.c index 6b04514..a2f74ac 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2569,6 +2569,8 @@ void mingw_startup(void) wchar_t **wenv, **wargv; _startupinfo si; + trace2_initialize_clock(); + maybe_redirect_std_handles(); /* get wide char arguments and environment */ diff --git a/trace2.c b/trace2.c index ccccd4e..6dd51e6 100644 --- a/trace2.c +++ b/trace2.c @@ -142,6 +142,11 @@ static void tr2main_signal_handler(int signo) raise(signo); } +void trace2_initialize_clock(void) +{ + tr2tls_start_process_clock(); +} + void trace2_initialize_fl(const char *file, int line) { struct tr2_tgt *tgt_j; @@ -428,7 +433,7 @@ void trace2_thread_start_fl(const char *file, int line, const char *thread_name) us_now = getnanotime() / 1000; us_elapsed_absolute = tr2tls_absolute_elapsed(us_now); - tr2tls_create_self(thread_name); + tr2tls_create_self(thread_name, us_now); for_each_wanted_builtin (j, tgt_j) if (tgt_j->pfn_thread_start_fl) diff --git a/trace2.h b/trace2.h index ae5020d..8f89e70 100644 --- a/trace2.h +++ b/trace2.h @@ -20,6 +20,23 @@ struct json_writer; */ /* + * Initialize the TRACE2 clock and do nothing else, in particular + * no mallocs, no system inspection, and no environment inspection. + * + * This should be called at the very top of main() to capture the + * process start time. This is intended to reduce chicken-n-egg + * bootstrap pressure. + * + * It is safe to call this more than once. This allows capturing + * absolute startup costs on Windows which uses a little trickery + * to do setup work before common-main.c:main() is called. + * + * The main trace2_initialize_fl() may be called a little later + * after more infrastructure is established. + */ +void trace2_initialize_clock(void); + +/* * Initialize TRACE2 tracing facility if any of the builtin TRACE2 * targets are enabled in the environment. Emits a 'version' event. * diff --git a/trace2/tr2_tls.c b/trace2/tr2_tls.c index 8e65b03..e76d8c5 100644 --- a/trace2/tr2_tls.c +++ b/trace2/tr2_tls.c @@ -10,16 +10,30 @@ #define TR2_REGION_NESTING_INITIAL_SIZE (100) static struct tr2tls_thread_ctx *tr2tls_thread_main; -static uint64_t tr2tls_us_start_main; +static uint64_t tr2tls_us_start_process; static pthread_mutex_t tr2tls_mutex; static pthread_key_t tr2tls_key; static int tr2_next_thread_id; /* modify under lock */ -struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name) +void tr2tls_start_process_clock(void) +{ + if (tr2tls_us_start_process) + return; + + /* + * Keep the absolute start time of the process (i.e. the main + * process) in a fixed variable since other threads need to + * access it. This allows them to do that without a lock on + * main thread's array data (because of reallocs). + */ + tr2tls_us_start_process = getnanotime() / 1000; +} + +struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name, + uint64_t us_thread_start) { - uint64_t us_now = getnanotime() / 1000; struct tr2tls_thread_ctx *ctx = xcalloc(1, sizeof(*ctx)); /* @@ -29,7 +43,7 @@ struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name) */ ctx->alloc = TR2_REGION_NESTING_INITIAL_SIZE; ctx->array_us_start = (uint64_t *)xcalloc(ctx->alloc, sizeof(uint64_t)); - ctx->array_us_start[ctx->nr_open_regions++] = us_now; + ctx->array_us_start[ctx->nr_open_regions++] = us_thread_start; ctx->thread_id = tr2tls_locked_increment(&tr2_next_thread_id); @@ -55,7 +69,7 @@ struct tr2tls_thread_ctx *tr2tls_get_self(void) * here and silently continue. */ if (!ctx) - ctx = tr2tls_create_self("unknown"); + ctx = tr2tls_create_self("unknown", getnanotime() / 1000); return ctx; } @@ -124,22 +138,18 @@ uint64_t tr2tls_absolute_elapsed(uint64_t us) if (!tr2tls_thread_main) return 0; - return us - tr2tls_us_start_main; + return us - tr2tls_us_start_process; } void tr2tls_init(void) { + tr2tls_start_process_clock(); + pthread_key_create(&tr2tls_key, NULL); init_recursive_mutex(&tr2tls_mutex); - tr2tls_thread_main = tr2tls_create_self("main"); - /* - * Keep a copy of the absolute start time of the main thread - * in a fixed variable since other threads need to access it. - * This also eliminates the need to lock accesses to the main - * thread's array (because of reallocs). - */ - tr2tls_us_start_main = tr2tls_thread_main->array_us_start[0]; + tr2tls_thread_main = + tr2tls_create_self("main", tr2tls_us_start_process); } void tr2tls_release(void) diff --git a/trace2/tr2_tls.h b/trace2/tr2_tls.h index bb80e3f..b1e327a 100644 --- a/trace2/tr2_tls.h +++ b/trace2/tr2_tls.h @@ -31,7 +31,8 @@ struct tr2tls_thread_ctx { * In this and all following functions the term "self" refers to the * current thread. */ -struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name); +struct tr2tls_thread_ctx *tr2tls_create_self(const char *thread_name, + uint64_t us_thread_start); /* * Get our TLS data. @@ -94,4 +95,9 @@ void tr2tls_release(void); */ int tr2tls_locked_increment(int *p); +/* + * Capture the process start time and do nothing else. + */ +void tr2tls_start_process_clock(void); + #endif /* TR2_TLS_H */ -- cgit v0.10.2-6-g49f6