X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=lib%2Ftimeval.h;h=1384848a1cec8f9b19087ce3c83413dd64e651a9;hb=25f78c28faf4f3e059a006c8423b701fe9e9e77c;hp=e8413ff25ca64caad18c3b9aa140ea3a9207e76c;hpb=e0edde6fee279cdbbf3c179f5f50adaf0c7c7f1e;p=openvswitch

diff --git a/lib/timeval.h b/lib/timeval.h
index e8413ff2..1384848a 100644
--- a/lib/timeval.h
+++ b/lib/timeval.h
@@ -36,6 +36,21 @@ BUILD_ASSERT_DECL(TYPE_IS_INTEGER(time_t));
  * ever encounter such a platform. */
 BUILD_ASSERT_DECL(TYPE_IS_SIGNED(time_t));
 
+/* On x86-64 systems, Linux avoids using syscalls for clock_gettime().
+ *
+ * For systems which do invoke a system call we wait at least
+ * TIME_UPDATE_INTERVAL ms between clock_gettime() calls and cache the time for
+ * the interim.
+ *
+ * For systems which do not invoke a system call, we just call clock_gettime()
+ * whenever the time is requested.  As a result we don't start the background
+ * SIGALRM timer unless explicitly needed by time_alarm() */
+#if defined __x86_64__ && defined __linux__
+#define CACHE_TIME 0
+#else
+#define CACHE_TIME 1
+#endif
+
 #define TIME_MAX TYPE_MAXIMUM(time_t)
 #define TIME_MIN TYPE_MINIMUM(time_t)