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>
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32
cache-tree.c
32
cache-tree.c
@ -631,3 +631,35 @@ void prime_cache_tree(struct cache_tree **it, struct tree *tree)
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*it = cache_tree();
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prime_cache_tree_rec(*it, tree);
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}
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/*
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* find the cache_tree that corresponds to the current level without
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* exploding the full path into textual form. The root of the
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* cache tree is given as "root", and our current level is "info".
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* (1) When at root level, info->prev is NULL, so it is "root" itself.
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* (2) Otherwise, find the cache_tree that corresponds to one level
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* above us, and find ourselves in there.
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*/
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static struct cache_tree *find_cache_tree_from_traversal(struct cache_tree *root,
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struct traverse_info *info)
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{
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struct cache_tree *our_parent;
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if (!info->prev)
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return root;
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our_parent = find_cache_tree_from_traversal(root, info->prev);
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return cache_tree_find(our_parent, info->name.path);
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}
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int cache_tree_matches_traversal(struct cache_tree *root,
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struct name_entry *ent,
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struct traverse_info *info)
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{
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struct cache_tree *it;
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it = find_cache_tree_from_traversal(root, info);
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it = cache_tree_find(it, ent->path);
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if (it && it->entry_count > 0 && !hashcmp(ent->sha1, it->sha1))
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return it->entry_count;
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return 0;
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}
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@ -2,6 +2,7 @@
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#define CACHE_TREE_H
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#include "tree.h"
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#include "tree-walk.h"
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struct cache_tree;
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struct cache_tree_sub {
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@ -42,4 +43,6 @@ int cache_tree_update(struct cache_tree *, struct cache_entry **, int, int, int)
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int write_cache_as_tree(unsigned char *sha1, int flags, const char *prefix);
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void prime_cache_tree(struct cache_tree **, struct tree *);
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extern int cache_tree_matches_traversal(struct cache_tree *, struct name_entry *ent, struct traverse_info *info);
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#endif
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@ -446,6 +446,7 @@ int run_diff_index(struct rev_info *revs, int cached)
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memset(&opts, 0, sizeof(opts));
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opts.head_idx = 1;
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opts.index_only = cached;
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opts.diff_index_cached = cached;
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opts.merge = 1;
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opts.fn = oneway_diff;
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opts.unpack_data = revs;
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@ -502,6 +503,7 @@ int do_diff_cache(const unsigned char *tree_sha1, struct diff_options *opt)
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memset(&opts, 0, sizeof(opts));
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opts.head_idx = 1;
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opts.index_only = 1;
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opts.diff_index_cached = 1;
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opts.merge = 1;
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opts.fn = oneway_diff;
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opts.unpack_data = &revs;
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@ -326,6 +326,23 @@ static int unpack_callback(int n, unsigned long mask, unsigned long dirmask, str
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if (src[0])
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conflicts |= 1;
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}
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/* special case: "diff-index --cached" looking at a tree */
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if (o->diff_index_cached &&
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n == 1 && dirmask == 1 && S_ISDIR(names->mode)) {
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int matches;
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matches = cache_tree_matches_traversal(o->src_index->cache_tree,
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names, info);
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/*
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* Everything under the name matches. Adjust o->pos to
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* skip the entire hierarchy.
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*/
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if (matches) {
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o->pos += matches;
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return mask;
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}
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}
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if (traverse_trees_recursive(n, dirmask, conflicts,
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names, info) < 0)
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return -1;
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@ -27,6 +27,7 @@ struct unpack_trees_options {
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aggressive:1,
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skip_unmerged:1,
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initial_checkout:1,
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diff_index_cached:1,
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gently:1;
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const char *prefix;
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int pos;
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