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show-branch: fix performance problem.

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The core function used in show-branch, join_revs(), was supposed
to be exactly the same algorithm as merge_bases(), except that
it was a version enhanced for use with more than two heads.
However, it needed to mark and keep a list of all the commits it
has seen, because it needed them for its semi-graphical output.
The function to implement this list, mark_seen(), stupidly used
insert_by_date(), when it did not need to keep the list sorted
during its processing.  This made "show-branch --merge-base"
more than 20x slower compared to "merge-base --all" in some
cases (e.g. between b5032a5 and 48ce8b0 in the Linux 2.6 kernel
archive).  The performance of "show-branch --independent"
suffered from the same reason.

This patch sorts the resulting list after the list traversal
just once to fix these problems.

Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Junio C Hamano
2006-07-16 00:00:09 -07:00
parent a3e65d74ee
commit 26a8ad25b2
1 changed files with 5 additions and 4 deletions
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9
builtin-show-branch.c
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@ -172,7 +172,7 @@ static void name_commits(struct commit_list *list,
static int mark_seen(struct commit *commit, struct commit_list **seen_p)
{
if (!commit->object.flags) {
insert_by_date(commit, seen_p);
commit_list_insert(commit, seen_p);
return 1;
}
return 0;
@ -218,9 +218,8 @@ static void join_revs(struct commit_list **list_p,
* Postprocess to complete well-poisoning.
*
* At this point we have all the commits we have seen in
* seen_p list (which happens to be sorted chronologically but
* it does not really matter). Mark anything that can be
* reached from uninteresting commits not interesting.
* seen_p list. Mark anything that can be reached from
* uninteresting commits not interesting.
*/
for (;;) {
int changed = 0;
@ -701,6 +700,8 @@ int cmd_show_branch(int ac, const char **av, char **envp)
if (0 <= extra)
join_revs(&list, &seen, num_rev, extra);
sort_by_date(&seen);
if (merge_base)
return show_merge_base(seen, num_rev);