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authorJunio C Hamano <gitster@pobox.com>2009-05-20 15:57:22 -0700
committerJunio C Hamano <gitster@pobox.com>2009-05-25 11:35:29 -0700
commitb65982b60876c8f5f4d3b2898d5174f4812552b1 (patch)
tree2589a99c5824624b4ff66249fd64214da84b1da1 /cache-tree.c
parentaceae2ef9261718324bf1853401d5ee9686a54a8 (diff)
downloadgit-b65982b60876c8f5f4d3b2898d5174f4812552b1.tar.gz
Optimize "diff-index --cached" using cache-tree
When running "diff-index --cached" after making a change to only a small portion of the index, there is no point unpacking unchanged subtrees into the index recursively, only to find that all entries match anyway. Tweak unpack_trees() logic that is used to read in the tree object to catch the case where the tree entry we are looking at matches the index as a whole by looking at the cache-tree. As an exercise, after modifying a few paths in the kernel tree, here are a few numbers on my Athlon 64X2 3800+: (without patch, hot cache) $ /usr/bin/time git diff --cached --raw :100644 100644 b57e1f5... e69de29... M Makefile :100644 000000 8c86b72... 0000000... D arch/x86/Makefile :000000 100644 0000000... e69de29... A arche 0.07user 0.02system 0:00.09elapsed 102%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+9407minor)pagefaults 0swaps (with patch, hot cache) $ /usr/bin/time ../git.git/git-diff --cached --raw :100644 100644 b57e1f5... e69de29... M Makefile :100644 000000 8c86b72... 0000000... D arch/x86/Makefile :000000 100644 0000000... e69de29... A arche 0.02user 0.00system 0:00.02elapsed 103%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+0outputs (0major+2446minor)pagefaults 0swaps Cold cache numbers are very impressive, but it does not matter very much in practice: (without patch, cold cache) $ su root sh -c 'echo 3 >/proc/sys/vm/drop_caches' $ /usr/bin/time git diff --cached --raw :100644 100644 b57e1f5... e69de29... M Makefile :100644 000000 8c86b72... 0000000... D arch/x86/Makefile :000000 100644 0000000... e69de29... A arche 0.06user 0.17system 0:10.26elapsed 2%CPU (0avgtext+0avgdata 0maxresident)k 247032inputs+0outputs (1172major+8237minor)pagefaults 0swaps (with patch, cold cache) $ su root sh -c 'echo 3 >/proc/sys/vm/drop_caches' $ /usr/bin/time ../git.git/git-diff --cached --raw :100644 100644 b57e1f5... e69de29... M Makefile :100644 000000 8c86b72... 0000000... D arch/x86/Makefile :000000 100644 0000000... e69de29... A arche 0.02user 0.01system 0:01.01elapsed 3%CPU (0avgtext+0avgdata 0maxresident)k 18440inputs+0outputs (79major+2369minor)pagefaults 0swaps This of course helps "git status" as well. (without patch, hot cache) $ /usr/bin/time ../git.git/git-status >/dev/null 0.17user 0.18system 0:00.35elapsed 100%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+5336outputs (0major+10970minor)pagefaults 0swaps (with patch, hot cache) $ /usr/bin/time ../git.git/git-status >/dev/null 0.10user 0.16system 0:00.27elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k 0inputs+5336outputs (0major+3921minor)pagefaults 0swaps Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'cache-tree.c')
-rw-r--r--cache-tree.c32
1 files changed, 32 insertions, 0 deletions
diff --git a/cache-tree.c b/cache-tree.c
index 5481e43340..16a65dfac1 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -631,3 +631,35 @@ void prime_cache_tree(struct cache_tree **it, struct tree *tree)
*it = cache_tree();
prime_cache_tree_rec(*it, tree);
}
+
+/*
+ * find the cache_tree that corresponds to the current level without
+ * exploding the full path into textual form. The root of the
+ * cache tree is given as "root", and our current level is "info".
+ * (1) When at root level, info->prev is NULL, so it is "root" itself.
+ * (2) Otherwise, find the cache_tree that corresponds to one level
+ * above us, and find ourselves in there.
+ */
+static struct cache_tree *find_cache_tree_from_traversal(struct cache_tree *root,
+ struct traverse_info *info)
+{
+ struct cache_tree *our_parent;
+
+ if (!info->prev)
+ return root;
+ our_parent = find_cache_tree_from_traversal(root, info->prev);
+ return cache_tree_find(our_parent, info->name.path);
+}
+
+int cache_tree_matches_traversal(struct cache_tree *root,
+ struct name_entry *ent,
+ struct traverse_info *info)
+{
+ struct cache_tree *it;
+
+ it = find_cache_tree_from_traversal(root, info);
+ it = cache_tree_find(it, ent->path);
+ if (it && it->entry_count > 0 && !hashcmp(ent->sha1, it->sha1))
+ return it->entry_count;
+ return 0;
+}