Revert "Break metadata into smaller chunks (number of chunks=10) for faster delta generation."

metadata.cc

 // Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <algorithm>
 #include <string>
 #include <vector>
 
 #include <base/string_util.h>
 #include <et/com_err.h>
@@ skipping 202 matching lines @@
   // until the end of the inode table.
   for (dgrp_t bg = 0; bg < fs_old->group_desc_count; bg++) {
     struct ext2_group_desc* group_desc = &fs_old->group_desc[bg];
     __u32 num_metadata_blocks = (group_desc->bg_inode_table +
                                  fs_old->inode_blocks_per_group) -
                                  (bg * fs_old->super->s_blocks_per_group);
     __u32 bg_start_block = bg * fs_old->super->s_blocks_per_group;
 
     // Due to bsdiff slowness, we're going to break each block group down
     // into metadata chunks and feed them to bsdiff.
-    __u32 num_chunks = 10;
+    __u32 num_chunks = 4;
     __u32 blocks_per_chunk = num_metadata_blocks / num_chunks;
     __u32 curr_block = bg_start_block;
     for (__u32 chunk = 0; chunk < num_chunks; chunk++) {
       Extent extent;
       if (chunk < num_chunks - 1) {
         extent = ExtentForRange(curr_block, blocks_per_chunk);
       } else {
         extent = ExtentForRange(curr_block,
                                 bg_start_block + num_metadata_blocks -
                                 curr_block);
@@ skipping 239 matching lines @@
                                           blocks,
                                           fs_old,
                                           fs_new,
                                           data_fd,
                                           data_file_size));
 
   return true;
 }
 
 };  // namespace chromeos_update_engine