зеркало из https://github.com/microsoft/git.git
combine-diff: speed it up, by using multiparent diff tree-walker directly
As was recently shown in "combine-diff: optimize combine_diff_path sets intersection", combine-diff runs very slowly. In that commit we optimized paths sets intersection, but that accounted only for ~ 25% of the slowness, and as my tracing showed, for linux.git v3.10..v3.11, for merges a lot of time is spent computing diff(commit,commit^2) just to only then intersect that huge diff to almost small set of files from diff(commit,commit^1). In previous commit, we described the problem in more details, and reworked the diff tree-walker to be general one - i.e. to work in multiple parent case too. Now is the time to take advantage of it for finding paths for combine diff. The implementation is straightforward - if we know, we can get generated diff paths directly, and at present that means no diff filtering or rename/copy detection was requested(*), we can call multiparent tree-walker directly and get ready paths. (*) because e.g. at present, all diffcore transformations work on diff_filepair queues, but in the future, that limitation can be lifted, if filters would operate directly on combine_diff_paths. Timings for `git log --raw --no-abbrev --no-renames` without `-c` ("git log") and with `-c` ("git log -c") and with `-c --merges` ("git log -c --merges") before and after the patch are as follows: linux.git v3.10..v3.11 log log -c log -c --merges before 1.9s 16.4s 15.2s after 1.9s 2.4s 1.1s The result stayed the same. Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru> Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Родитель
72441af7c4
Коммит
7195fbfaf5
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@ -1303,7 +1303,7 @@ static const char *path_path(void *obj)
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/* find set of paths that every parent touches */
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static struct combine_diff_path *find_paths(const unsigned char *sha1,
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static struct combine_diff_path *find_paths_generic(const unsigned char *sha1,
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const struct sha1_array *parents, struct diff_options *opt)
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{
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struct combine_diff_path *paths = NULL;
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@ -1316,6 +1316,7 @@ static struct combine_diff_path *find_paths(const unsigned char *sha1,
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/* tell diff_tree to emit paths in sorted (=tree) order */
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opt->orderfile = NULL;
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/* D(A,P1...Pn) = D(A,P1) ^ ... ^ D(A,Pn) (wrt paths) */
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for (i = 0; i < num_parent; i++) {
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/*
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* show stat against the first parent even when doing
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@ -1346,6 +1347,35 @@ static struct combine_diff_path *find_paths(const unsigned char *sha1,
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}
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/*
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* find set of paths that everybody touches, assuming diff is run without
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* rename/copy detection, etc, comparing all trees simultaneously (= faster).
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*/
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static struct combine_diff_path *find_paths_multitree(
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const unsigned char *sha1, const struct sha1_array *parents,
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struct diff_options *opt)
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{
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int i, nparent = parents->nr;
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const unsigned char **parents_sha1;
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struct combine_diff_path paths_head;
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struct strbuf base;
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parents_sha1 = xmalloc(nparent * sizeof(parents_sha1[0]));
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for (i = 0; i < nparent; i++)
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parents_sha1[i] = parents->sha1[i];
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/* fake list head, so worker can assume it is non-NULL */
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paths_head.next = NULL;
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strbuf_init(&base, PATH_MAX);
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diff_tree_paths(&paths_head, sha1, parents_sha1, nparent, &base, opt);
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strbuf_release(&base);
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free(parents_sha1);
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return paths_head.next;
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}
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void diff_tree_combined(const unsigned char *sha1,
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const struct sha1_array *parents,
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int dense,
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@ -1355,6 +1385,7 @@ void diff_tree_combined(const unsigned char *sha1,
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struct diff_options diffopts;
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struct combine_diff_path *p, *paths;
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int i, num_paths, needsep, show_log_first, num_parent = parents->nr;
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int need_generic_pathscan;
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/* nothing to do, if no parents */
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if (!num_parent)
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@ -1377,11 +1408,58 @@ void diff_tree_combined(const unsigned char *sha1,
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/* find set of paths that everybody touches
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*
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* NOTE find_paths() also handles --stat, as it computes
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* diff(sha1,parent_i) for all i to do the job, specifically
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* for parent0.
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* NOTE
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*
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* Diffcore transformations are bound to diff_filespec and logic
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* comparing two entries - i.e. they do not apply directly to combine
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* diff.
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*
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* If some of such transformations is requested - we launch generic
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* path scanning, which works significantly slower compared to
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* simultaneous all-trees-in-one-go scan in find_paths_multitree().
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*
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* TODO some of the filters could be ported to work on
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* combine_diff_paths - i.e. all functionality that skips paths, so in
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* theory, we could end up having only multitree path scanning.
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*
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* NOTE please keep this semantically in sync with diffcore_std()
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*/
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paths = find_paths(sha1, parents, &diffopts);
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need_generic_pathscan = opt->skip_stat_unmatch ||
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DIFF_OPT_TST(opt, FOLLOW_RENAMES) ||
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opt->break_opt != -1 ||
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opt->detect_rename ||
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opt->pickaxe ||
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opt->filter;
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if (need_generic_pathscan) {
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/*
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* NOTE generic case also handles --stat, as it computes
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* diff(sha1,parent_i) for all i to do the job, specifically
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* for parent0.
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*/
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paths = find_paths_generic(sha1, parents, &diffopts);
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}
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else {
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int stat_opt;
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paths = find_paths_multitree(sha1, parents, &diffopts);
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/*
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* show stat against the first parent even
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* when doing combined diff.
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*/
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stat_opt = (opt->output_format &
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(DIFF_FORMAT_NUMSTAT|DIFF_FORMAT_DIFFSTAT));
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if (stat_opt) {
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diffopts.output_format = stat_opt;
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diff_tree_sha1(parents->sha1[0], sha1, "", &diffopts);
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diffcore_std(&diffopts);
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if (opt->orderfile)
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diffcore_order(opt->orderfile);
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diff_flush(&diffopts);
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}
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}
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/* find out number of surviving paths */
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for (num_paths = 0, p = paths; p; p = p->next)
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1
diff.c
1
diff.c
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@ -4764,6 +4764,7 @@ void diffcore_fix_diff_index(struct diff_options *options)
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void diffcore_std(struct diff_options *options)
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{
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/* NOTE please keep the following in sync with diff_tree_combined() */
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if (options->skip_stat_unmatch)
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diffcore_skip_stat_unmatch(options);
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if (!options->found_follow) {
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