Use higher resolution clock for uptime on Linux (if available).

cmake/configure.cmake

@@ -2,7 +2,8 @@
 # configure node for building
 #
 include(CheckFunctionExists)
-
+include(CheckLibraryExists)
+include(CheckSymbolExists)
 
 if(NOT "v${CMAKE_BUILD_TYPE}" MATCHES vDebug)
   set(CMAKE_BUILD_TYPE "Release")
@@ -72,6 +73,20 @@ else()
   add_definitions(-DHAVE_FDATASYNC=0)
 endif()
 
+# check first without rt and then with rt
+check_function_exists(clock_gettime HAVE_CLOCK_GETTIME)
+check_library_exists(rt clock_gettime "" HAVE_CLOCK_GETTIME_RT)
+
+if(HAVE_CLOCK_GETTIME OR HAVE_CLOCK_GETTIME_RT)
+  check_symbol_exists(CLOCK_MONOTONIC "time.h" HAVE_MONOTONIC_CLOCK)
+endif()
+
+if(HAVE_MONOTONIC_CLOCK)
+  add_definitions(-DHAVE_MONOTONIC_CLOCK=1)
+else()
+  add_definitions(-DHAVE_MONOTONIC_CLOCK=0)
+endif()
+
 if(DTRACE)
   if(NOT ${node_platform} MATCHES sunos)
     message(FATAL_ERROR "DTrace support only currently available on Solaris")

src/platform_linux.cc

@@ -15,6 +15,10 @@
 #include <stdlib.h> // free
 #include <string.h> // strdup
 
+#if HAVE_MONOTONIC_CLOCK
+#include <time.h>
+#endif
+
 namespace node {
 
 using namespace v8;
@@ -240,13 +244,21 @@ double Platform::GetTotalMemory() {
 }
 
 double Platform::GetUptimeImpl() {
+#if HAVE_MONOTONIC_CLOCK
+  struct timespec now;
+  if (0 == clock_gettime(CLOCK_MONOTONIC, &now)) {
+    double uptime = now.tv_sec;
+    uptime += (double)now.tv_nsec / 1000000000.0;
+    return uptime;
+  }
+  return -1;
+#else
   struct sysinfo info;
-
   if (sysinfo(&info) < 0) {
     return -1;
   }
-
   return static_cast<double>(info.uptime);
+#endif
 }
 
 int Platform::GetLoadAvg(Local<Array> *loads) {

wscript

@@ -328,7 +328,24 @@ def configure(conf):
   elif 'DEST_CPU' in conf.env and conf.env['DEST_CPU']:
     conf.env['DEST_CPU'] = canonical_cpu_type(conf.env['DEST_CPU'])
 
-  conf.check(lib='rt', uselib_store='RT')
+  have_librt = conf.check(lib='rt', uselib_store='RT')
+
+  have_monotonic = False
+  if have_librt:
+    code =  """
+      #include <time.h>
+      int main(void) {
+        struct timespec now;
+        clock_gettime(CLOCK_MONOTONIC, &now);
+        return 0;
+      }
+    """
+    have_monotonic = conf.check_cc(lib="rt", msg="Checking for CLOCK_MONOTONIC", fragment=code)
+
+  if have_monotonic:
+    conf.env.append_value('CPPFLAGS', '-DHAVE_MONOTONIC_CLOCK=1')
+  else:
+    conf.env.append_value('CPPFLAGS', '-DHAVE_MONOTONIC_CLOCK=0')
 
   if sys.platform.startswith("sunos"):
     if not conf.check(lib='socket', uselib_store="SOCKET"):