Minimize the number of branches, and orce the correct prediction for the

most usual one. Most of the time we expect the functions which allocate
requests to succeed.

This commit was SVN r12344.

ompi/mca/pml/ob1/pml_ob1_sendreq.c

@@ -16,8 +16,10 @@
  * $HEADER$
  */
 
-
 #include "ompi_config.h"
+
+#include "opal/prefetch.h"
+
 #include "ompi/constants.h"
 #include "ompi/mca/pml/pml.h"
 #include "ompi/mca/btl/btl.h"
@@ -470,35 +472,39 @@ int mca_pml_ob1_send_request_start_copy(
     mca_pml_ob1_hdr_t* hdr;
     struct iovec iov;
     unsigned int iov_count;
-    size_t max_data;
+    size_t max_data = size;
     int rc;
 
     /* allocate descriptor */
-    if(0==size)
-        MCA_PML_OB1_DES_ALLOC(bml_btl, descriptor,
-                sizeof(mca_pml_ob1_match_hdr_t));
-    else
-        mca_bml_base_alloc(bml_btl, &descriptor,
-                sizeof(mca_pml_ob1_match_hdr_t) + size);
-    if(NULL == descriptor) {
-        return OMPI_ERR_OUT_OF_RESOURCE;
-    } 
-    segment = descriptor->des_src;
+    if( 0 == size ) {
+        MCA_PML_OB1_DES_ALLOC( bml_btl, descriptor,
+                               sizeof(mca_pml_ob1_match_hdr_t) );
+	if( OPAL_UNLIKELY(NULL == descriptor) ) {
+	    return OMPI_ERR_OUT_OF_RESOURCE;
+	}
+	segment = descriptor->des_src;
+	descriptor->des_cbfunc = mca_pml_ob1_match_completion_cache;
+    } else {
+        mca_bml_base_alloc( bml_btl, &descriptor,
+			    sizeof(mca_pml_ob1_match_hdr_t) + size );
+	if( OPAL_UNLIKELY(NULL == descriptor) ) {
+	    return OMPI_ERR_OUT_OF_RESOURCE;
+	}
+	segment = descriptor->des_src;
 
-    max_data = size;
-    if(size > 0) { 
-        /* pack the data into the supplied buffer */
-        iov.iov_base = (IOVBASE_TYPE*)((unsigned char*)segment->seg_addr.pval + sizeof(mca_pml_ob1_match_hdr_t));
-        iov.iov_len = size;
-        iov_count = 1;
-        if((rc = ompi_convertor_pack(
-                                     &sendreq->req_send.req_convertor,
-                                     &iov,
-                                     &iov_count,
-                                     &max_data)) < 0) {
-            mca_bml_base_free(bml_btl, descriptor);
-            return rc;
-        }
+	/* pack the data into the supplied buffer */
+	iov.iov_base = (IOVBASE_TYPE*)((unsigned char*)segment->seg_addr.pval + sizeof(mca_pml_ob1_match_hdr_t));
+	iov.iov_len = size;
+	iov_count = 1;
+	rc = ompi_convertor_pack( &sendreq->req_send.req_convertor,
+                                  &iov,
+                                  &iov_count,
+                                  &max_data );
+	if( OPAL_UNLIKELY(rc < 0) ) {
+	    mca_bml_base_free(bml_btl, descriptor);
+	    return rc;
+	}
+	descriptor->des_cbfunc = mca_pml_ob1_match_completion_free;
     }
     
     /* build match header */
@@ -530,8 +536,6 @@ int mca_pml_ob1_send_request_start_copy(
     sendreq->req_rdma_offset = max_data;
 
     /* short message */
-    descriptor->des_cbfunc = size?mca_pml_ob1_match_completion_free:
-        mca_pml_ob1_match_completion_cache;
     descriptor->des_flags |= MCA_BTL_DES_FLAGS_PRIORITY;
     descriptor->des_cbdata = sendreq;
 
@@ -542,8 +546,8 @@ int mca_pml_ob1_send_request_start_copy(
 
     /* send */
     rc = mca_bml_base_send(bml_btl, descriptor, MCA_BTL_TAG_PML);
-    if(OMPI_SUCCESS != rc) {
-        if(0==size)
+    if( OPAL_UNLIKELY(OMPI_SUCCESS != rc) ) {
+        if( 0 == size )
             MCA_BML_BASE_BTL_DES_RETURN(bml_btl, descriptor);
         else
             mca_bml_base_free(bml_btl, descriptor );