diff -ur ddumbfs-1.1.orig/src/ddfslib.c ddumbfs-1.1/src/ddfslib.c
--- ddumbfs-1.1.orig/src/ddfslib.c	2013-01-12 07:13:30.000000000 +0800
+++ ddumbfs-1.1/src/ddfslib.c	2014-12-08 09:42:28.202953103 +0800
@@ -1479,6 +1479,10 @@
 
     }
 
+    if(!ddfs->lock_index) {
+	madvise(ddfs->nodes, ddfs->c_node_block_count*ddfs->c_index_block_size, MADV_RANDOM);
+    }
+
     long long int i;
     unsigned char c=0;
     for (i=0; i<ddfs->c_node_block_count; i++)
diff -ur ddumbfs-1.1.orig/src/ddumbfs.c ddumbfs-1.1/src/ddumbfs.c
--- ddumbfs-1.1.orig/src/ddumbfs.c	2013-01-12 07:13:30.000000000 +0800
+++ ddumbfs-1.1/src/ddumbfs.c	2014-12-16 13:01:43.530299723 +0800
@@ -354,8 +352,8 @@
 
 void preload_node(long long int node_idx)
 {  // make a read in nodes to load the page, usually just before to lock the mutex
-    char ch=*(ddfs->nodes+(node_idx*ddfs->c_node_size));
+    volatile char ch=*(ddfs->nodes+(node_idx*ddfs->c_node_size));
     (void)ch;
 }
 
 #define ddumb_get_fh(fi) ((struct ddumb_fh *)(uintptr_t)(fi)->fh)
@@ -1479,8 +1480,8 @@
     // update statistic
     ddumb_statistic.block_write_try_next_node+=res-1; // should use the number of try in ddfs_locate_hash
 
-    // save the used block list at regular interval
-    ddumbfs_save_usedblocks(16000);
+    // save the used block list at regular interval (approx 2GB)
+    ddumbfs_save_usedblocks(16000 * (131072 / ddfs->c_block_size));
 
     // the hash is not found, search a free block in the BlockFile
     long long int baddr=ddfs_alloc_block();
@@ -1811,7 +1822,7 @@
         if (res<0) return res;
     }
 
-    DDFS_LOG(LOG_NOTICE, "[%lu]++  ddumb_getattr %s size=%lld\n", thread_id(), path, (long long int)stbuf->st_size);
+    //DDFS_LOG(LOG_NOTICE, "[%lu]++  ddumb_getattr %s size=%lld\n", thread_id(), path, (long long int)stbuf->st_size);
     return 0;
 }
 
@@ -2773,7 +2784,7 @@
 
         // save_usedblocks ?
         pthread_mutex_lock_d(&ifile_mutex);
-        if (res==ETIMEDOUT) ddumbfs_save_usedblocks(1000);
+        if (res==ETIMEDOUT) ddumbfs_save_usedblocks(1000 * (131072 / ddfs->c_block_size));
         else ddumbfs_save_usedblocks(0);
         pthread_mutex_unlock_d(&ifile_mutex);