make the opal progress yield variable settable at any time

The semantics of the variable mpi_yield_when_idle are to call
opal_progress_set_yield_when_idle at MPI_Init. It would be difficult
to modify the old variable to support setting this parameter at
runtime. The fix is to add an additional parameter to opal:
opal_progress_yield_when_idle that directly sets the variable. This
variable is settable anytime and does not affect the semantics of
the old mpi_yield_when_idle variable.

Refs trac:193

cmr=v1.8.1:reviewer=jsquyres

This commit was SVN r31255.

The following Trac tickets were found above:
  Ticket 193 --> https://svn.open-mpi.org/trac/ompi/ticket/193

opal/runtime/opal_params.c

@@ -1,3 +1,4 @@
+/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
@@ -13,7 +14,7 @@
  *                         reserved. 
  * Copyright (c) 2008-2012 Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2009      Oak Ridge National Labs.  All rights reserved.
- * Copyright (c) 2010-2013 Los Alamos National Security, LLC.
+ * Copyright (c) 2010-2014 Los Alamos National Security, LLC.
  *                         All rights reserved.
  * Copyright (c) 2014      Hochschule Esslingen.  All rights reserved.
  * $COPYRIGHT$
@@ -104,6 +105,15 @@ int opal_register_params(void)
 	}
     }
 
+#if defined(HAVE_SCHED_YIELD)
+    opal_progress_yield_when_idle = false;
+    ret = mca_base_var_register ("opal", "opal", "progress", "yield_when_idle",
+                                 "Yield the processor when waiting on progress",
+                                 MCA_BASE_VAR_TYPE_BOOL, NULL, 0, MCA_BASE_VAR_FLAG_SETTABLE,
+                                 OPAL_INFO_LVL_8, MCA_BASE_VAR_SCOPE_LOCAL,
+                                 &opal_progress_yield_when_idle);
+#endif
+
 #if OPAL_ENABLE_DEBUG
     opal_progress_debug = false;
     ret = mca_base_var_register ("opal", "opal", "progress", "debug",

opal/runtime/opal_progress.c

@@ -1,3 +1,4 @@
+/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
@@ -9,7 +10,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2006-2013 Los Alamos National Security, LLC.  All rights
+ * Copyright (c) 2006-2014 Los Alamos National Security, LLC.  All rights
  *                         reserved. 
  *
  * $COPYRIGHT$
@@ -57,7 +58,7 @@ static size_t callbacks_len = 0;
 static size_t callbacks_size = 0;
 
 /* do we want to call sched_yield() if nothing happened */
-static int call_yield = 1;
+bool opal_progress_yield_when_idle;
 
 #if OPAL_PROGRESS_USE_TIMERS
 static opal_timer_t event_progress_last_time = 0;
@@ -105,7 +106,7 @@ opal_progress_init(void)
     OPAL_OUTPUT((debug_output, "progress: initialized event flag to: %x",
                  opal_progress_event_flag));                 
     OPAL_OUTPUT((debug_output, "progress: initialized yield_when_idle to: %s",
-                 call_yield == 0 ? "false" : "true"));
+                 opal_progress_yield_when_idle ? "true" : "false"));
     OPAL_OUTPUT((debug_output, "progress: initialized num users to: %d",
                  num_event_users));
     OPAL_OUTPUT((debug_output, "progress: initialized poll rate to: %ld",
@@ -187,7 +188,7 @@ opal_progress(void)
     }
 
 #if defined(HAVE_SCHED_YIELD)
-    if (call_yield && events <= 0) {
+    if (opal_progress_yield_when_idle && events <= 0) {
         /* If there is nothing to do - yield the processor - otherwise
          * we could consume the processor for the entire time slice. If
          * the processor is oversubscribed - this will result in a best-case
@@ -249,11 +250,11 @@ opal_progress_event_users_decrement(void)
 bool
 opal_progress_set_yield_when_idle(bool yieldopt)
 {
-    bool tmp = (call_yield == 0) ? false : true;
-    call_yield = (yieldopt) ? 1 : 0;
+    bool tmp = opal_progress_yield_when_idle;
+    opal_progress_yield_when_idle = (yieldopt) ? 1 : 0;
 
     OPAL_OUTPUT((debug_output, "progress: progress_set_yield_when_idle to %s",
-                                    call_yield == 0 ? "false" : "true"));
+                                    opal_progress_yield_when_idle ? "true" : "false"));
 
     return tmp;
 }

opal/runtime/opal_progress.h

@@ -1,4 +1,4 @@
-/*
+/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- *//*
  * Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
  *                         University Research and Technology
  *                         Corporation.  All rights reserved.
@@ -9,7 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2006      Los Alamos National Security, LLC.  All rights
+ * Copyright (c) 2006-2014 Los Alamos National Security, LLC.  All rights
  *                         reserved. 
  *
  * $COPYRIGHT$
@@ -175,6 +175,9 @@ OPAL_DECLSPEC int opal_progress_unregister(opal_progress_callback_t cb);
 
 OPAL_DECLSPEC extern int opal_progress_spin_count;
 
+/* do we want to call sched_yield() if nothing happened */
+OPAL_DECLSPEC extern bool opal_progress_yield_when_idle;
+
 /**
  * Progress until flag is true or poll iterations completed
  */