Enable yield cycle on Linux

This change allows the runtime to turn __kmp_yield() on/off repeatedly on Linux.
This feature was removed when disabling monitor thread, but there are
applications that perform better with this feature on.

Patch by Hansang Bae

Differential Revision: https://reviews.llvm.org/D29227

llvm-svn: 295203

1 files changed, 8 insertions, 5 deletions

diff --git a/openmp/runtime/src/z_Linux_util.cpp b/openmp/runtime/src/z_Linux_util.cpp
index b9490ea65d3..8cba1ff5607 100644
--- a/openmp/runtime/src/z_Linux_util.cpp
+++ b/openmp/runtime/src/z_Linux_util.cpp
@@ -1812,13 +1812,16 @@ __kmp_resume_monitor()
 void
 __kmp_yield( int cond )
 {
-    if (cond
+    if (!cond)
+        return;
 #if KMP_USE_MONITOR
-        && __kmp_yielding_on
+    if (!__kmp_yielding_on)
+        return;
+#else
+    if (__kmp_yield_cycle && !KMP_YIELD_NOW())
+        return;
 #endif
-    ) {
-        sched_yield();
-    }
+    sched_yield();
 }
 
 /* ------------------------------------------------------------------------ */