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Commit bb86e1d9 authored by Tianjie Xu's avatar Tianjie Xu
Browse files

Adjust the size limit for splitting large files 

Modify the number of max blocks per transfer to reduce splitting of
large files during patch generation. This will reduce the size of
final incremental OTA updater package. In specific, the size limit
for each file to transfer is set to 1/8 cachesize instead of a fix
number.

Bug: 26472126

Change-Id: Iffb135e378c4c7a91640f2fc4c40e9e93d1fe4bb
parent c610c42b

tools/releasetools/blockimgdiff.py

+18 −11
Original line number Diff line number Diff line
@@ -987,29 +987,36 @@ class BlockImageDiff(object): 
      too many blocks (greater than MAX_BLOCKS_PER_DIFF_TRANSFER), we split it

      into smaller pieces by getting multiple Transfer()s.



      The downside is that after splitting, we can no longer use imgdiff but

      only bsdiff."""



      MAX_BLOCKS_PER_DIFF_TRANSFER = 1024

      The downside is that after splitting, we may increase the package size

      since the split pieces don't align well. According to our experiments,

      1/8 of the cache size as the per-piece limit appears to be optimal.

      Compared to the fixed 1024-block limit, it reduces the overall package

      size by 30% volantis, and 20% for angler and bullhead."""



      # We care about diff transfers only.

      if style != "diff" or not split:

        Transfer(tgt_name, src_name, tgt_ranges, src_ranges, style, by_id)

        return



      pieces = 0

      cache_size = common.OPTIONS.cache_size

      split_threshold = 0.125

      max_blocks_per_transfer = int(cache_size * split_threshold /

                                    self.tgt.blocksize)



      # Change nothing for small files.

      if (tgt_ranges.size() <= MAX_BLOCKS_PER_DIFF_TRANSFER and

          src_ranges.size() <= MAX_BLOCKS_PER_DIFF_TRANSFER):

      if (tgt_ranges.size() <= max_blocks_per_transfer and

          src_ranges.size() <= max_blocks_per_transfer):

        Transfer(tgt_name, src_name, tgt_ranges, src_ranges, style, by_id)

        return



      pieces = 0

      while (tgt_ranges.size() > MAX_BLOCKS_PER_DIFF_TRANSFER and

             src_ranges.size() > MAX_BLOCKS_PER_DIFF_TRANSFER):

      while (tgt_ranges.size() > max_blocks_per_transfer and

             src_ranges.size() > max_blocks_per_transfer):

        tgt_split_name = "%s-%d" % (tgt_name, pieces)

        src_split_name = "%s-%d" % (src_name, pieces)

        tgt_first = tgt_ranges.first(MAX_BLOCKS_PER_DIFF_TRANSFER)

        src_first = src_ranges.first(MAX_BLOCKS_PER_DIFF_TRANSFER)

        tgt_first = tgt_ranges.first(max_blocks_per_transfer)

        src_first = src_ranges.first(max_blocks_per_transfer)



        Transfer(tgt_split_name, src_split_name, tgt_first, src_first, style,

                 by_id)