bml/r2: always add btl progress function

This commit changes the behavior of bml/r2 from conditionally
registering btl progress functions to always registering progress
functions. Any progress function beloning to a btl that is not yet in
use is registered as low-priority. As soon as a proc is added that
will make use of the btl is is re-registered normally.

This works around an issue with some btls. In order to progress a
first message from an unknown peer both ugni and openib need to have
their progress functions called. If either btl is not in use after the
first call to add_procs the callback was never happening. This commit
ensures the btl progress function is called at some point but the
number of progress callbacks is reduced from normal to ensure lower
overhead when a btl is not used. The current ratio is 1 low priority
progress callback for every 8 calls to opal_progress().

Fixes open-mpi/ompi#1676

Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>

ompi/mca/bml/r2/bml_r2.c

@@ -166,22 +166,30 @@ static mca_bml_base_endpoint_t *mca_bml_r2_allocate_endpoint (ompi_proc_t *proc)
     return bml_endpoint;
 }
 
-static void mca_bml_r2_register_progress (mca_btl_base_module_t *btl)
+static void mca_bml_r2_register_progress (mca_btl_base_module_t *btl, bool hp)
 {
     if (NULL != btl->btl_component->btl_progress) {
         bool found = false;
+        size_t p;
 
-        for (size_t p = 0 ; p < mca_bml_r2.num_btl_progress ; ++p) {
+        for (p = 0 ; p < mca_bml_r2.num_btl_progress ; ++p) {
             if(mca_bml_r2.btl_progress[p] == btl->btl_component->btl_progress) {
                 found = true;
                 break;
             }
         }
 
-        if (found == false) {
-            mca_bml_r2.btl_progress[mca_bml_r2.num_btl_progress++] =
-                btl->btl_component->btl_progress;
-            opal_progress_register (btl->btl_component->btl_progress);
+        if (found == false || hp) {
+            if (found == false) {
+                mca_bml_r2.btl_progress[mca_bml_r2.num_btl_progress++] =
+                    btl->btl_component->btl_progress;
+            }
+
+            if (hp) {
+                opal_progress_register (btl->btl_component->btl_progress);
+            } else {
+                opal_progress_register_lp (btl->btl_component->btl_progress);
+            }
         }
     }
 }
@@ -405,7 +413,7 @@ static int mca_bml_r2_add_proc (struct ompi_proc_t *proc)
         if (OMPI_SUCCESS != rc) {
             btl->btl_del_procs (btl, 1, (opal_proc_t **) &proc, &btl_endpoint);
         } else {
-            mca_bml_r2_register_progress (btl);
+            mca_bml_r2_register_progress (btl, true);
             btl_in_use = true;
         }
     }
@@ -546,9 +554,7 @@ static int mca_bml_r2_add_procs( size_t nprocs,
             btl_inuse++;
         }
 
-        if (btl_inuse) {
-            mca_bml_r2_register_progress (btl);
-        }
+        mca_bml_r2_register_progress (btl, !!(btl_inuse));
     }
 
     free(btl_endpoints);

opal/runtime/opal_progress.c

@@ -10,7 +10,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2006-2014 Los Alamos National Security, LLC.  All rights
+ * Copyright (c) 2006-2016 Los Alamos National Security, LLC.  All rights
  *                         reserved.
  * Copyright (c) 2015-2016 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
@@ -59,6 +59,10 @@ static opal_progress_callback_t *callbacks = NULL;
 static size_t callbacks_len = 0;
 static size_t callbacks_size = 0;
 
+static opal_progress_callback_t *callbacks_lp = NULL;
+static size_t callbacks_lp_len = 0;
+static size_t callbacks_lp_size = 0;
+
 /* do we want to call sched_yield() if nothing happened */
 bool opal_progress_yield_when_idle = false;
 
@@ -151,6 +155,7 @@ opal_progress_finalize(void)
 void
 opal_progress(void)
 {
+    static volatile uint64_t num_calls = 0;
     size_t i;
     int events = 0;
 
@@ -189,6 +194,13 @@ opal_progress(void)
         events += (callbacks[i])();
     }
 
+    if ((OPAL_THREAD_ADD64((volatile int64_t *) &num_calls, 1) & 0x7) == 0) {
+        /* run low priority callbacks once every 8 calls to opal_progress() */
+        for (i = 0 ; i < callbacks_lp_len ; ++i) {
+            events += (callbacks_lp[i])();
+        }
+    }
+
 #if OPAL_HAVE_SCHED_YIELD
     if (opal_progress_yield_when_idle && events <= 0) {
         /* If there is nothing to do - yield the processor - otherwise
@@ -317,6 +329,9 @@ opal_progress_register(opal_progress_callback_t cb)
     int ret = OPAL_SUCCESS;
     size_t index;
 
+    /* just in case there is a low-priority callback remove it */
+    (void) opal_progress_unregister (cb);
+
     opal_atomic_lock(&progress_lock);
 
     /* see if we need to allocate more space */
@@ -345,17 +360,53 @@ opal_progress_register(opal_progress_callback_t cb)
     return ret;
 }
 
-int
-opal_progress_unregister(opal_progress_callback_t cb)
+int opal_progress_register_lp (opal_progress_callback_t cb)
+{
+    int ret = OPAL_SUCCESS;
+    size_t index;
+
+    /* just in case there is a high-priority callback remove it */
+    (void) opal_progress_unregister (cb);
+
+    opal_atomic_lock(&progress_lock);
+
+    /* see if we need to allocate more space */
+    if (callbacks_lp_len + 1 > callbacks_lp_size) {
+        opal_progress_callback_t *tmp;
+        tmp = (opal_progress_callback_t*)realloc(callbacks_lp, sizeof(opal_progress_callback_t) * (callbacks_lp_size + 4));
+        if (tmp == NULL) {
+            ret = OPAL_ERR_TEMP_OUT_OF_RESOURCE;
+            goto cleanup;
+        }
+        /* registering fake callbacks_lp to fill callbacks_lp[] */
+        for( index = callbacks_lp_len + 1 ;  index < callbacks_lp_size + 4 ; index++) {
+            tmp[index] = &fake_cb;
+        }
+
+        callbacks_lp = tmp;
+        callbacks_lp_size += 4;
+    }
+
+    callbacks_lp[callbacks_lp_len++] = cb;
+
+ cleanup:
+
+    opal_atomic_unlock(&progress_lock);
+
+    return ret;
+}
+
+static int _opal_progress_unregister (opal_progress_callback_t cb, opal_progress_callback_t *callback_array,
+                                      size_t callback_array_len)
 {
     size_t i;
     int ret = OPAL_ERR_NOT_FOUND;
 
     opal_atomic_lock(&progress_lock);
 
-    for (i = 0 ; i < callbacks_len ; ++i) {
-        if (cb == callbacks[i]) {
-            callbacks[i] = &fake_cb;
+    for (i = 0 ; i < callback_array_len ; ++i) {
+        if (cb == callback_array[i]) {
+            callback_array[i] = &fake_cb;
             ret = OPAL_SUCCESS;
             break;
         }
@@ -367,17 +418,28 @@ opal_progress_unregister(opal_progress_callback_t cb)
        do any repacking.  size_t can be unsigned, so 0 - 1 is bad for
        a loop condition :). */
     if (OPAL_SUCCESS == ret) {
-        if (callbacks_len > 1 ) {
-            /* now tightly pack the array */
-            for ( ; i < callbacks_len - 1 ; ++i) {
-                callbacks[i] = callbacks[i + 1];
-            }
+        if (i < callback_array_len - 1) {
+            memmove (callback_array + i, callback_array + i + 1,
+                     (callback_array_len - i - 1) * sizeof (callback_array[0]));
         }
-        callbacks[callbacks_len - 1] = &fake_cb;
-        callbacks_len--;
+
+        callback_array[callback_array_len - 1] = &fake_cb;
+        callback_array_len--;
     }
 
     opal_atomic_unlock(&progress_lock);
 
     return ret;
 }
+
+int opal_progress_unregister (opal_progress_callback_t cb)
+{
+    int ret = _opal_progress_unregister (cb, callbacks, callbacks_len);
+    if (OPAL_SUCCESS != ret) {
+        /* if not in the high-priority array try to remove from the lp array.
+         * a callback will never be in both. */
+        return _opal_progress_unregister (cb, callbacks_lp, callbacks_lp_len);
+    }
+
+    return ret;
+}

opal/runtime/opal_progress.h

@@ -163,6 +163,8 @@ typedef int (*opal_progress_callback_t)(void);
  */
 OPAL_DECLSPEC int opal_progress_register(opal_progress_callback_t cb);
 
+OPAL_DECLSPEC int opal_progress_register_lp (opal_progress_callback_t cb);
+
 
 /**
  * Deregister previously registered event