Add support for clock_gettime

Use the more accurate clock under Linux when available. getrusage()
unfortunately only has a resolution of 1/HZ (i.e., one jiffie), which
is too coarse-grained in many cases.

2 files changed, 29 insertions, 0 deletions

diff --git a/native/Makefile b/native/Makefile
index f9fbb75..80c8310 100644
--- a/native/Makefile
+++ b/native/Makefile
@@ -36,6 +36,11 @@ PYTHON_LIB ?=
 SOFLAGS     = -shared
 endif
 
+# Support for clock_gettime()
+ifeq ($(OS),Linux)
+LIBS += -lrt
+endif
+
 CXXFLAGS  = -Wall -Wextra $(DISABLED_WARNINGS) -fPIC $(INCLUDES)
 LDFLAGS   = $(LIBS)
 SWIGFLAGS = -python -c++ -outdir . -includeall -Iinclude
diff --git a/native/src/cpu_time.cpp b/native/src/cpu_time.cpp
index a7dfa6d..d003f22 100644
--- a/native/src/cpu_time.cpp
+++ b/native/src/cpu_time.cpp
@@ -1,9 +1,32 @@
 
+#include <time.h>
 #include <sys/time.h>
 #include <sys/resource.h>
 
 #include "cpu_time.h"
 
+
+#if _POSIX_C_SOURCE >= 199309L
+
+// use clock_xxx() API
+
+double get_cpu_usage(void)
+{
+        struct timespec ts;
+
+        if (clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts) == 0)
+        {
+                return ts.tv_sec + ts.tv_nsec / 1E9;
+        }
+        else
+                return 0.0;
+}
+
+
+#else
+
+// fall back to getrusage()
+
 #ifdef RUSAGE_THREAD
 // This is a Linuxism...
 #define ACCOUNTING_SCOPE RUSAGE_THREAD
@@ -23,3 +46,4 @@ double get_cpu_usage(void)
                 return 0.0;
 }
 
+#endif