Performance tuning. make sure we catch if the user wants to set the default fileview and replace it with

our optimized default file view. Otherwise, performance will suffer. file_get_view should still return the correct filetype, not our optimized default file view

ompi/mca/io/ompio/io_ompio.c

@@ -100,14 +100,15 @@ static int mca_io_ompio_merge_initial_groups(mca_io_ompio_file_t *fh,
 static int mca_io_ompio_merge_groups(mca_io_ompio_file_t *fh,
                                      int *merge_aggrs,
                                      int num_merge_aggrs);
-
-
+ 
+#define MCA_IO_OMPIO_DEFAULT_FVIEW_SIZE 4*1024*1024
+ompi_datatype_t *mca_io_ompio_default_file_view=NULL;
 
 int ompi_io_ompio_set_file_defaults (mca_io_ompio_file_t *fh)
 {
 
    if (NULL != fh) {
-        ompi_datatype_t *types[2], *default_file_view;
+        ompi_datatype_t *types[2];
         int blocklen[2] = {1, 1};
         OPAL_PTRDIFF_TYPE d[2], base;
         int i;
@@ -133,13 +134,13 @@ int ompi_io_ompio_set_file_defaults (mca_io_ompio_file_t *fh)
         fh->f_init_num_aggrs = -1;
         fh->f_init_aggr_list = NULL;
 
-	ompi_datatype_create_contiguous(1048576,
+	ompi_datatype_create_contiguous(MCA_IO_OMPIO_DEFAULT_FVIEW_SIZE,
 					&ompi_mpi_byte.dt,
-					&default_file_view);
-	ompi_datatype_commit (&default_file_view);
+					&mca_io_ompio_default_file_view);
+	ompi_datatype_commit (&mca_io_ompio_default_file_view);
 
 	fh->f_etype = &ompi_mpi_byte.dt;
-	fh->f_filetype =  default_file_view;
+	fh->f_filetype =  mca_io_ompio_default_file_view;
 
 
         /* Default file View */
@@ -151,9 +152,10 @@ int ompi_io_ompio_set_file_defaults (mca_io_ompio_file_t *fh)
 	mca_io_ompio_set_view_internal(fh,
 				       0,
 				       &ompi_mpi_byte.dt,
-				       default_file_view,
+				       mca_io_ompio_default_file_view,
 				       "native",
 				       fh->f_info);
+        fh->f_flags |= OMPIO_FILE_VIEW_IS_SET;
 
 
 	/*Create a derived datatype for the created iovec */

ompi/mca/io/ompio/io_ompio_file_set_view.c

@@ -38,6 +38,7 @@
 #include "io_ompio.h"
 
 static OMPI_MPI_OFFSET_TYPE get_contiguous_chunk_size (mca_io_ompio_file_t *);
+extern ompi_datatype_t *mca_io_ompio_default_file_view;
 
 
 int mca_io_ompio_set_view_internal(mca_io_ompio_file_t *fh,
@@ -139,6 +140,23 @@ int mca_io_ompio_file_set_view (ompi_file_t *fp,
     data = (mca_io_ompio_data_t *) fp->f_io_selected_data;
     fh = &data->ompio_fh;
 
+    if ( fh->f_flags & OMPIO_FILE_VIEW_IS_SET ) {
+	if ( MPI_BYTE == etype && MPI_BYTE == filetype ) {
+	    /* this is the default file view that the user provides. If we also have the default file view set
+	    ** dont replace our optimized version  of the default file view with 
+            ** MPI_BYTE/MPI_BYTE, since the performance suffers terribly
+            ** if you do that.  Otherwise, pass the optimized version along, not the trivial version.    
+	    */
+	    if ( mca_io_ompio_default_file_view == fh->f_filetype ) {
+		/* don't do anything */
+		return OMPI_SUCCESS;
+	    }
+	    else {
+		filetype = mca_io_ompio_default_file_view;
+	    }
+	}		     
+    }
+
     if (NULL != fh->f_decoded_iov) {
         free (fh->f_decoded_iov);
         fh->f_decoded_iov = NULL;
@@ -186,7 +204,12 @@ int mca_io_ompio_file_get_view (struct ompi_file_t *fp,
 
     *disp = fh->f_disp;
     ompi_datatype_duplicate (fh->f_etype, etype);
-    ompi_datatype_duplicate (fh->f_filetype, filetype);
+    if ( mca_io_ompio_default_file_view == fh->f_filetype ) {
+	ompi_datatype_duplicate ( &ompi_mpi_byte.dt, filetype);
+    }
+    else {
+	ompi_datatype_duplicate (fh->f_filetype, filetype);
+    }
     strcpy (datarep, fh->f_datarep);
 
     return OMPI_SUCCESS;