From: Junio C Hamano Date: Wed, 20 May 2009 22:57:22 +0000 (-0700) Subject: Optimize "diff-index --cached" using cache-tree X-Git-Tag: v1.6.4-rc0~45^2~1 X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=b65982b60876c8f5f4d3b2898d5174f4812552b1;p=git.git 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 --- diff --git a/cache-tree.c b/cache-tree.c index 5481e4334..16a65dfac 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; +} diff --git a/cache-tree.h b/cache-tree.h index eadcad8ad..3df641f59 100644 --- a/cache-tree.h +++ b/cache-tree.h @@ -2,6 +2,7 @@ #define CACHE_TREE_H #include "tree.h" +#include "tree-walk.h" struct cache_tree; struct cache_tree_sub { @@ -42,4 +43,6 @@ int cache_tree_update(struct cache_tree *, struct cache_entry **, int, int, int) int write_cache_as_tree(unsigned char *sha1, int flags, const char *prefix); void prime_cache_tree(struct cache_tree **, struct tree *); +extern int cache_tree_matches_traversal(struct cache_tree *, struct name_entry *ent, struct traverse_info *info); + #endif diff --git a/diff-lib.c b/diff-lib.c index a310fb2ad..1cb97af22 100644 --- a/diff-lib.c +++ b/diff-lib.c @@ -446,6 +446,7 @@ int run_diff_index(struct rev_info *revs, int cached) memset(&opts, 0, sizeof(opts)); opts.head_idx = 1; opts.index_only = cached; + opts.diff_index_cached = cached; opts.merge = 1; opts.fn = oneway_diff; opts.unpack_data = revs; @@ -502,6 +503,7 @@ int do_diff_cache(const unsigned char *tree_sha1, struct diff_options *opt) memset(&opts, 0, sizeof(opts)); opts.head_idx = 1; opts.index_only = 1; + opts.diff_index_cached = 1; opts.merge = 1; opts.fn = oneway_diff; opts.unpack_data = &revs; diff --git a/unpack-trees.c b/unpack-trees.c index aaacaf101..8eb3ddb39 100644 --- a/unpack-trees.c +++ b/unpack-trees.c @@ -326,6 +326,23 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str if (src[0]) conflicts |= 1; } + + /* special case: "diff-index --cached" looking at a tree */ + if (o->diff_index_cached && + n == 1 && dirmask == 1 && S_ISDIR(names->mode)) { + int matches; + matches = cache_tree_matches_traversal(o->src_index->cache_tree, + names, info); + /* + * Everything under the name matches. Adjust o->pos to + * skip the entire hierarchy. + */ + if (matches) { + o->pos += matches; + return mask; + } + } + if (traverse_trees_recursive(n, dirmask, conflicts, names, info) < 0) return -1; diff --git a/unpack-trees.h b/unpack-trees.h index 0d26f3d73..1e0e2325f 100644 --- a/unpack-trees.h +++ b/unpack-trees.h @@ -27,6 +27,7 @@ struct unpack_trees_options { aggressive:1, skip_unmerged:1, initial_checkout:1, + diff_index_cached:1, gently:1; const char *prefix; int pos;