Don't always fill with zeros. Fixes #917. Gives some speedups on random.

git-svn-id: file:///svn/tokudb@4543 c7de825b-a66e-492c-adef-691d508d4ae1

newbrt/brt-internal.h

@@ -50,6 +50,7 @@ typedef struct brtnode *BRTNODE;
 struct brtnode {
     enum typ_tag tag;
     unsigned int nodesize;
+    int ever_been_written;
     unsigned int flags;
     DISKOFF thisnodename;   // The size of the node allocated on disk.  Not all is necessarily in use.
     //  These two LSNs are used to decide when to make a copy of a node instead of overwriting it.

newbrt/brt-serialize.c

@@ -197,9 +197,12 @@ void toku_serialize_brtnode_to (int fd, DISKOFF off, BRTNODE node) {
 
     //write_now: printf("%s:%d Writing %d bytes\n", __FILE__, __LINE__, w.ndone);
     {
-	ssize_t r=pwrite(fd, w.buf, (size_t)node->nodesize, off); // write the whole buffer, including the zeros
+	// If the node has never been written, then write the whole buffer, including the zeros
+	//size_t n_to_write = node->nodesize;
+	size_t n_to_write = node->ever_been_written ? w.ndone : node->nodesize;
+	ssize_t r=pwrite(fd, w.buf, n_to_write, off);
 	if (r<0) printf("r=%ld errno=%d\n", (long)r, errno);
-	assert(r==(ssize_t)node->nodesize);
+	assert(r==(ssize_t)n_to_write);
     }
 
     if (calculated_size!=w.ndone)
@@ -222,6 +225,7 @@ int toku_deserialize_brtnode_from (int fd, DISKOFF off, BRTNODE *brtnode) {
 	if (0) { died0: toku_free(result); }
 	return r;
     }
+    result->ever_been_written = 1; 
     {
 	u_int32_t datasize_n;
 	r = pread(fd, &datasize_n, sizeof(datasize_n), off +8+4+8);

newbrt/brt.c

@@ -366,6 +366,7 @@ int toku_create_new_brtnode (BRT t, BRTNODE *result, int height, TOKULOGGER logg
     assert(n);
     assert(t->h->nodesize>0);
     //printf("%s:%d malloced %lld (and malloc again=%lld)\n", __FILE__, __LINE__, name, malloc_diskblock(t, t->nodesize));
+    n->ever_been_written = 0;
     initialize_brtnode(t, n, name, height);
     *result = n;
     assert(n->nodesize>0);
@@ -1872,6 +1873,7 @@ static int setup_initial_brt_root_node (BRT t, DISKOFF offset, TOKULOGGER logger
     int r;
     TAGMALLOC(BRTNODE, node);
     assert(node);
+    node->ever_been_written = 0;
     //printf("%s:%d\n", __FILE__, __LINE__);
     initialize_brtnode(t, node,
 		       offset, /* the location is one nodesize offset from 0. */
@@ -2269,6 +2271,7 @@ static int brt_init_new_root(BRT brt, BRTNODE nodea, BRTNODE nodeb, DBT splitk,
     r=malloc_diskblock(&newroot_diskoff, brt, new_nodesize, logger);
     assert(r==0);
     assert(newroot);
+    newroot->ever_been_written = 0;
     if (brt->database_name==0) {
 	toku_log_changeunnamedroot(logger, (LSN*)0, 0, toku_cachefile_filenum(brt->cf), *rootp, newroot_diskoff);
     } else {

newbrt/tests/brt-serialize-test.c

@@ -23,6 +23,7 @@ static void test_serialize(void) {
     //    source_brt.fd=fd;
     char *hello_string;
     sn.nodesize = nodesize;
+    sn.ever_been_written = 0;
     sn.flags = 0x11223344;
     sn.thisnodename = sn.nodesize*20;
     sn.disk_lsn.lsn = 789;