[PATCH 1/6] Don't try to delta if target is much smaller than source
- From
Brian Downing <bdowning@lavos.net>
- Date
- Jul 12, 2007, 12:55 UTC
- Message-ID
- <11842449523154-git-send-email-bdowning@lavos.net>
- In-Reply-To
- <1184244952554-git-send-email-bdowning@lavos.net>
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@lavos.net> --- 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