[svn-r2472] Combine object header prefix and first object header chunk when possible.

1 files changed, 55 insertions, 20 deletions

diff --git a/src/H5O.c b/src/H5O.c
index 5d1fe99..a064da1 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -542,6 +542,7 @@ H5O_flush(H5F_t *f, hbool_t destroy, haddr_t addr, H5O_t *oh)
     intn	i, id;
     H5O_cont_t	*cont = NULL;
     herr_t	(*encode)(H5F_t*, uint8_t*, const void*) = NULL;
+    uintn combine=0;        /* Whether to combine the object header prefix & the first chunk */
 
     FUNC_ENTER(H5O_flush, FAIL);
 
@@ -572,16 +573,22 @@ H5O_flush(H5F_t *f, hbool_t destroy, haddr_t addr, H5O_t *oh)
 	/* zero to alignment */
 	HDmemset (p, 0, H5O_SIZEOF_HDR(f)-12);
 
-	/* write the object header header */
+	/* write the object header prefix */
+    /* Check if we can combine the object header prefix & the first chunk into one I/O operation */
+    if(oh->chunk[0].dirty && (addr+H5O_SIZEOF_HDR(f))==oh->chunk[0].addr) {
+        combine=1;
+    } /* end if */
+    else {
 #ifdef H5_HAVE_PARALLEL
-	if (IS_H5FD_MPIO(f))
-	    H5FD_mpio_tas_allsame(f->shared->lf, TRUE); /*only p0 will write*/
+        if (IS_H5FD_MPIO(f))
+            H5FD_mpio_tas_allsame(f->shared->lf, TRUE); /*only p0 will write*/
 #endif /* H5_HAVE_PARALLEL */
-	if (H5F_block_write(f, addr, (hsize_t)H5O_SIZEOF_HDR(f), 
-			    H5P_DEFAULT, buf) < 0) {
-	    HRETURN_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL,
-			  "unable to write object header hdr to disk");
-	}
+        if (H5F_block_write(f, addr, (hsize_t)H5O_SIZEOF_HDR(f), 
+                    H5P_DEFAULT, buf) < 0) {
+            HRETURN_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL,
+                  "unable to write object header hdr to disk");
+        }
+    } /* end else */
 	
 	/* encode messages */
 	for (i = 0; i < oh->nmesgs; i++) {
@@ -649,20 +656,48 @@ H5O_flush(H5F_t *f, hbool_t destroy, haddr_t addr, H5O_t *oh)
 	/* write each chunk to disk */
 	for (i = 0; i < oh->nchunks; i++) {
 	    if (oh->chunk[i].dirty) {
-		assert(H5F_addr_defined(oh->chunk[i].addr));
+            assert(H5F_addr_defined(oh->chunk[i].addr));
+            if(i==0 && combine) {
+                /* Allocate space for the combined prefix and first chunk */
+                if((p=H5FL_BLK_ALLOC(chunk_image,H5O_SIZEOF_HDR(f)+oh->chunk[i].size,0))==NULL)
+                    HRETURN_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed");
+
+                /* Copy in the prefix */
+                HDmemcpy(p,buf,H5O_SIZEOF_HDR(f));
+
+                /* Copy in the first chunk */
+                HDmemcpy(p+H5O_SIZEOF_HDR(f),oh->chunk[i].image,oh->chunk[i].size);
+
+                /* Write the combined prefix/chunk out */
 #ifdef H5_HAVE_PARALLEL
-	    if (IS_H5FD_MPIO(f))
-		H5FD_mpio_tas_allsame(f->shared->lf, TRUE); /*only p0 write*/
+                if (IS_H5FD_MPIO(f))
+                    H5FD_mpio_tas_allsame(f->shared->lf, TRUE); /*only p0 write*/
 #endif /* H5_HAVE_PARALLEL */
-		if (H5F_block_write(f, oh->chunk[i].addr,
-				    (hsize_t)(oh->chunk[i].size),
-				    H5P_DEFAULT, oh->chunk[i].image) < 0) {
-		    HRETURN_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL,
-			      "unable to write object header data to disk");
-		}
-		oh->chunk[i].dirty = FALSE;
-	    }
-	}
+                if (H5F_block_write(f, addr,
+                            (hsize_t)(H5O_SIZEOF_HDR(f)+oh->chunk[i].size),
+                            H5P_DEFAULT, p) < 0) {
+                    HRETURN_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL,
+                          "unable to write object header data to disk");
+                } /* end if */
+
+                /* Release the memory for the combined prefix/chunk */
+                p = H5FL_BLK_FREE(chunk_image,p);
+            } /* end if */
+            else {
+#ifdef H5_HAVE_PARALLEL
+                if (IS_H5FD_MPIO(f))
+                H5FD_mpio_tas_allsame(f->shared->lf, TRUE); /*only p0 write*/
+#endif /* H5_HAVE_PARALLEL */
+                if (H5F_block_write(f, oh->chunk[i].addr,
+                            (hsize_t)(oh->chunk[i].size),
+                            H5P_DEFAULT, oh->chunk[i].image) < 0) {
+                    HRETURN_ERROR(H5E_OHDR, H5E_WRITEERROR, FAIL,
+                          "unable to write object header data to disk");
+                } /* end if */
+            } /* end else */
+            oh->chunk[i].dirty = FALSE;
+	    } /* end if */
+	} /* end for */
 	oh->dirty = FALSE;
     }