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
diff --git a/tools/releasetools/blockimgdiff.py b/tools/releasetools/blockimgdiff.py
index 1a5b93d..cef0c6f 100644
--- a/tools/releasetools/blockimgdiff.py
+++ b/tools/releasetools/blockimgdiff.py
@@ -987,29 +987,36 @@
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)
