Improve GC::Profiler.total_time accuracy

gistfile1.diff

diff --git a/gc.c b/gc.c
index e65d0ec..0f14a2f 100644
--- a/gc.c
+++ b/gc.c
@@ -127,7 +127,13 @@ typedef struct gc_profile_record {
 static double
 getrusage_time(void)
 {
-#ifdef RUSAGE_SELF
+#if defined(HAVE_CLOCK_GETTIME) && defined(CLOCK_PROCESS_CPUTIME_ID)
+    struct timespec ts;
+
+    if (clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts) == 0) {
+        return ts.tv_sec + ts.tv_nsec * 1e-9;
+    }
+#elif defined RUSAGE_SELF
     struct rusage usage;
     struct timeval time;
     getrusage(RUSAGE_SELF, &usage);

http://bugs.ruby-lang.org/issues/7500