Re: [PATCH 4/4] Invalidate cache-tree entries for touched paths in git-apply.

[Junio C Hamano <junkio@cox.net>]

Junio C Hamano <junkio@cox.net> writes:

>  * ... then the big rock falls.  With this, I tried to apply and
>    then write-tree "diff-tree -p $commit^1 $commit" on top of
>    "$commit^1" for the last 20 or so commits in the kernel tree.
>    The "master" version takes 0.15 second per patch on my Duron
>    750 with 700MB, while this one does that in 0.06 second.
>    This also helps the memory pressure because we do not have to
>    regenerate unchanged trees.  810 minor faults with the patch
>    vs 2150 minor faults without.

Sorry, but not really.  The patch is wrong and the measurement
was flawed.

It was doing unnecessarily more work in git-apply, which made
git-write-tree a no-op, and I was measuring only git-write-tree.

The following goes on top of the series to remove that
unnecessary work from git-apply.  Unfortunately this makes the
overall combination a bit slower than before X-<.

But I have not optimized cache-tree.c for speed; for example,
its subtree lists are not even sorted.  Once that is done we may
get decent speedups from the combo.

---
diff --git a/apply.c b/apply.c
index 5fa2c1e..e283df3 100644
--- a/apply.c
+++ b/apply.c
@@ -1935,8 +1935,6 @@ static int apply_patch(int fd, const cha
 				  active_cache_sha1) ||
 		    commit_index_file(&cache_file))
 			die("Unable to write new cachefile");
-		cache_tree_update(active_cache_tree,
-				  active_cache, active_nr, 1);
 		write_cache_tree(active_cache_sha1, active_cache_tree);
 	}