[PATCH] read-tree --aggressive
"Peter Eriksen" <s022018@student.dtu.dk> writes:
Show 7 quoted lines
> In connection with Ian Molton's question about merge have I played a
> little with 'git merge' on the kernel sources. What I find is that a
> merge can take quite some time, but I'm not sure where that time exactly
> goes to. Here are the times I got:
>
> Recursive (default): 4m22.282s
> Resolve (-s resolve): 3m23.548s
In your sample script, you do not disable the post-merge diff, which is typically one of the most expensive part in the whole merge, and I am wondering how fast a machine you are using to get 4 minutes. The post-merge diff is generated by piping the output of 'diff-tree -M' to 'apply --stat --summary', and that step alone takes about 12 minutes wallclock time on my box X-<.
Since my box is not as fast as yours, I've eliminated the post-merge diff step and tried your final merge step like this:
$ time git merge --no-summary -s resolve \
'Merging happily' HEAD v2.6.15 >/dev/nulland got this:
real 2m15.737s
user 1m43.320s
sys 0m26.690sWith the attached patch, the most expensive part, which is the repeated invocation of git-merge-one-file to remove many deleted paths, is eliminated. The result is this.
real 0m20.311s
user 0m15.780s
sys 0m4.150sThis patch would not help recursive strategy, though. Calling read-tree with --aggressive flag essentially disables the benefit we would expect to get from it -- rename detection.
-- >8 -- A new flag --aggressive resolves what we traditionally resolved with external git-merge-one-file inside index while read-tree 3-way merge works.
git-merge-octopus and git-merge-resolve use this flag before running git-merge-index with git-merge-one-file.
Signed-off-by: Junio C Hamano <junkio@cox.net>
---
git-merge-octopus.sh | 2 +-
git-merge-resolve.sh | 2 +-
read-tree.c | 32 ++++++++++++++++++++++++++++++++
3 files changed, 34 insertions(+), 2 deletions(-)
2a4bb6bc618bdad6529d9ffe361bc8b7dd28a56c
diff --git a/git-merge-octopus.sh b/git-merge-octopus.sh
index eb74f96..eb3f473 100755
--- a/git-merge-octopus.sh
+++ b/git-merge-octopus.sh
@@ -90,7 +90,7 @@ do
NON_FF_MERGE=1
echo "Trying simple merge with $SHA1"
- git-read-tree -u -m $common $MRT $SHA1 || exit 2
+ git-read-tree -u -m --aggressive $common $MRT $SHA1 || exit 2
next=$(git-write-tree 2>/dev/null)
if test $? -ne 0
then
diff --git a/git-merge-resolve.sh b/git-merge-resolve.sh
index 966e81f..0a8ef21 100755
--- a/git-merge-resolve.sh
+++ b/git-merge-resolve.sh
@@ -38,7 +38,7 @@ then
fi
git-update-index --refresh 2>/dev/null
-git-read-tree -u -m $bases $head $remotes || exit 2
+git-read-tree -u -m --aggressive $bases $head $remotes || exit 2
echo "Trying simple merge."
if result_tree=$(git-write-tree 2>/dev/null)
then
diff --git a/read-tree.c b/read-tree.c
index a46c6fe..5580f15 100644
--- a/read-tree.c
+++ b/read-tree.c
@@ -15,6 +15,7 @@ static int update = 0;
static int index_only = 0;
static int nontrivial_merge = 0;
static int trivial_merges_only = 0;
+static int aggressive = 0;
static int head_idx = -1;
static int merge_size = 0;
@@ -424,11 +425,14 @@ static int threeway_merge(struct cache_e
int df_conflict_remote = 0;
int any_anc_missing = 0;
+ int no_anc_exists = 1;
int i;
for (i = 1; i < head_idx; i++) {
if (!stages[i])
any_anc_missing = 1;
+ else
+ no_anc_exists = 0;
}
index = stages[0];
@@ -489,6 +493,29 @@ static int threeway_merge(struct cache_e
if (!head && !remote && any_anc_missing)
return 0;
+ /* Under the new "aggressive" rule, we resolve mostly trivial
+ * cases that we historically had git-merge-one-file resolve.
+ */
+ if (aggressive) {
+ int head_deleted = !head && !df_conflict_head;
+ int remote_deleted = !remote && !df_conflict_remote;
+ /*
+ * Deleted in both.
+ * Deleted in one and unchanged in the other.
+ */
+ if ((head_deleted && remote_deleted) ||
+ (head_deleted && remote && remote_match) ||
+ (remote_deleted && head && head_match))
+ return 0;
+
+ /*
+ * Added in both, identically.
+ */
+ if (no_anc_exists && head && remote && same(head, remote))
+ return merged_entry(head, index);
+
+ }
+
/* Below are "no merge" cases, which require that the index be
* up-to-date to avoid the files getting overwritten with
* conflict resolution files.
@@ -677,6 +704,11 @@ int main(int argc, char **argv)
continue;
}
+ if (!strcmp(arg, "--aggressive")) {
+ aggressive = 1;
+ continue;
+ }
+
/* "-m" stands for "merge", meaning we start in stage 1 */
if (!strcmp(arg, "-m")) {
if (stage || merge)
--
1.1.6.ge2129
