src: unify uptime base used across the code base

This patch joins `per_process::prog_start_time` (a double)
and `performance::performance_node_start` (a uint64_t) into a
`per_process::node_start_time` (a uint64_t) which gets initialized
in `node::Start()`.

PR-URL: https://github.com/nodejs/node/pull/26016
Reviewed-By: Anna Henningsen <anna@addaleax.net>

src/env.cc

@@ -228,9 +228,8 @@ Environment::Environment(IsolateData* isolate_data,
   performance_state_.reset(new performance::performance_state(isolate()));
   performance_state_->Mark(
       performance::NODE_PERFORMANCE_MILESTONE_ENVIRONMENT);
-  performance_state_->Mark(
-      performance::NODE_PERFORMANCE_MILESTONE_NODE_START,
-      performance::performance_node_start);
+  performance_state_->Mark(performance::NODE_PERFORMANCE_MILESTONE_NODE_START,
+                           per_process::node_start_time);
   performance_state_->Mark(
       performance::NODE_PERFORMANCE_MILESTONE_V8_START,
       performance::performance_v8_start);

src/node.cc

@@ -145,8 +145,8 @@ unsigned int reverted_cve = 0;
 bool v8_initialized = false;
 
 // node_internals.h
-// process-relative uptime base, initialized at start-up
-double prog_start_time;
+// process-relative uptime base in nanoseconds, initialized in node::Start()
+uint64_t node_start_time;
 // Tells whether --prof is passed.
 bool v8_is_profiling = false;
 
@@ -611,9 +611,6 @@ int ProcessGlobalArgs(std::vector<std::string>* args,
 int Init(std::vector<std::string>* argv,
          std::vector<std::string>* exec_argv,
          std::vector<std::string>* errors) {
-  // Initialize prog_start_time to get relative uptime.
-  per_process::prog_start_time = static_cast<double>(uv_now(uv_default_loop()));
-
   // Register built-in modules
   binding::RegisterBuiltinModules();
 
@@ -891,7 +888,7 @@ inline int Start(uv_loop_t* event_loop,
 int Start(int argc, char** argv) {
   atexit([] () { uv_tty_reset_mode(); });
   PlatformInit();
-  performance::performance_node_start = PERFORMANCE_NOW();
+  per_process::node_start_time = uv_hrtime();
 
   CHECK_GT(argc, 0);
 

src/node_internals.h

@@ -55,7 +55,7 @@ class NativeModuleLoader;
 
 namespace per_process {
 extern Mutex env_var_mutex;
-extern double prog_start_time;
+extern uint64_t node_start_time;
 extern bool v8_is_profiling;
 }  // namespace per_process
 

src/node_perf.cc

@@ -46,7 +46,6 @@ using v8::Value;
 const uint64_t timeOrigin = PERFORMANCE_NOW();
 // https://w3c.github.io/hr-time/#dfn-time-origin-timestamp
 const double timeOriginTimestamp = GetCurrentTimeInMicroseconds();
-uint64_t performance_node_start;
 uint64_t performance_v8_start;
 
 void performance_state::Mark(enum PerformanceMilestone milestone,

src/node_perf_common.h

@@ -18,7 +18,6 @@ namespace performance {
 
 // These occur before the environment is created. Cache them
 // here and add them to the milestones when the env is init'd.
-extern uint64_t performance_node_start;
 extern uint64_t performance_v8_start;
 
 #define NODE_PERFORMANCE_MILESTONES(V)                                        \

src/node_process_methods.cc

@@ -44,6 +44,7 @@ using v8::Isolate;
 using v8::Local;
 using v8::Name;
 using v8::NewStringType;
+using v8::Number;
 using v8::Object;
 using v8::String;
 using v8::Uint32;
@@ -58,6 +59,8 @@ Mutex umask_mutex;
 #define MICROS_PER_SEC 1e6
 // used in Hrtime() below
 #define NANOS_PER_SEC 1000000000
+// Used in Uptime()
+#define NANOS_PER_MICROS 1e3
 
 #ifdef _WIN32
 /* MAX_PATH is in characters, not bytes. Make sure we have enough headroom. */
@@ -239,12 +242,12 @@ static void Umask(const FunctionCallbackInfo<Value>& args) {
 
 static void Uptime(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
-  double uptime;
 
   uv_update_time(env->event_loop());
-  uptime = uv_now(env->event_loop()) - per_process::prog_start_time;
-
-  args.GetReturnValue().Set(uptime / 1000);
+  double uptime =
+      static_cast<double>(uv_hrtime() - per_process::node_start_time);
+  Local<Number> result = Number::New(env->isolate(), uptime / NANOS_PER_MICROS);
+  args.GetReturnValue().Set(result);
 }
 
 static void GetActiveRequests(const FunctionCallbackInfo<Value>& args) {

src/node_report.cc

@@ -47,6 +47,9 @@
 extern char** environ;
 #endif
 
+constexpr int NANOS_PER_SEC = 1000 * 1000 * 1000;
+constexpr double SEC_PER_MICROS = 1e-6;
+
 namespace report {
 using node::arraysize;
 using node::Environment;
@@ -489,20 +492,19 @@ static void PrintGCStatistics(JSONWriter* writer, Isolate* isolate) {
 #ifndef _WIN32
 // Report resource usage (Linux/OSX only).
 static void PrintResourceUsage(JSONWriter* writer) {
-  time_t current_time;  // current time absolute
-  time(&current_time);
-  size_t boot_time = static_cast<time_t>(node::per_process::prog_start_time /
-                                         (1000 * 1000 * 1000));
-  auto uptime = difftime(current_time, boot_time);
+  // Get process uptime in seconds
+  uint64_t uptime =
+      (uv_hrtime() - node::per_process::node_start_time) / (NANOS_PER_SEC);
   if (uptime == 0) uptime = 1;  // avoid division by zero.
 
   // Process and current thread usage statistics
   struct rusage stats;
   writer->json_objectstart("resourceUsage");
   if (getrusage(RUSAGE_SELF, &stats) == 0) {
-    double user_cpu = stats.ru_utime.tv_sec + 0.000001 * stats.ru_utime.tv_usec;
+    double user_cpu =
+        stats.ru_utime.tv_sec + SEC_PER_MICROS * stats.ru_utime.tv_usec;
     double kernel_cpu =
-        stats.ru_utime.tv_sec + 0.000001 * stats.ru_utime.tv_usec;
+        stats.ru_utime.tv_sec + SEC_PER_MICROS * stats.ru_utime.tv_usec;
     writer->json_keyvalue("userCpuSeconds", user_cpu);
     writer->json_keyvalue("kernelCpuSeconds", kernel_cpu);
     double cpu_abs = user_cpu + kernel_cpu;
@@ -522,9 +524,10 @@ static void PrintResourceUsage(JSONWriter* writer) {
 #ifdef RUSAGE_THREAD
   if (getrusage(RUSAGE_THREAD, &stats) == 0) {
     writer->json_objectstart("uvthreadResourceUsage");
-    double user_cpu = stats.ru_utime.tv_sec + 0.000001 * stats.ru_utime.tv_usec;
+    double user_cpu =
+        stats.ru_utime.tv_sec + SEC_PER_MICROS * stats.ru_utime.tv_usec;
     double kernel_cpu =
-        stats.ru_utime.tv_sec + 0.000001 * stats.ru_utime.tv_usec;
+        stats.ru_utime.tv_sec + SEC_PER_MICROS * stats.ru_utime.tv_usec;
     writer->json_keyvalue("userCpuSeconds", user_cpu);
     writer->json_keyvalue("kernelCpuSeconds", kernel_cpu);
     double cpu_abs = user_cpu + kernel_cpu;