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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 /diff-lib.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 'diff-lib.c')
-rw-r--r--diff-lib.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/diff-lib.c b/diff-lib.c
index a310fb2ad0..1cb97af22d 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;