Add a new try_delta heuristic: Don't bother trying to make a delta if
the target object size is much smaller (currently 1/32) than the source,
as it's very likely not going to get a match. Even if it does, you will
have to read at least 32x the size of the new file to reassemble it,
which isn't such a good deal. This leads to a considerable performance
improvement when deltifying a mix of small and large files with a very
large window, because you don't have to wait for the large files to
percolate out of the window before things start going fast again.
Signed-off-by: Brian Downing <bdowning@xxxxxxxxx>
---
builtin-pack-objects.c | 2 ++
1 files changed, 2 insertions(+), 0 deletions(-)
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 54b9d26..132ce96 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c
@@ -1342,6 +1342,8 @@ static int try_delta(struct unpacked *trg, struct unpacked *src,
sizediff = src_size < trg_size ? trg_size - src_size : 0;
if (sizediff >= max_size)
return 0;
+ if (trg_size < src_size / 32)
+ return 0;
/* Load data if not already done */
if (!trg->data) {
--
1.5.2.GIT
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