git@vger.kernel.org mailing list mirror (one of many)
 help / Atom feed
From: Ævar Arnfjörð Bjarmason  <avarab@gmail.com>
To: git@vger.kernel.org
Cc: Junio C Hamano <gitster@pobox.com>, Jeff King <peff@peff.net>,
	Ævar Arnfjörð Bjarmason  <avarab@gmail.com>
Subject: [PATCH 1/4] tag: speed up --contains calculation
Date: Sat, 11 Jun 2011 19:04:08 +0000
Message-ID: <1307819051-25748-2-git-send-email-avarab@gmail.com> (raw)
In-Reply-To: <1307819051-25748-1-git-send-email-avarab@gmail.com>

From: Jeff King <peff@peff.net>

When we want to know if commit A contains commit B (or any
one of a set of commits, B through Z), we generally
calculate the merge bases and see if B is a merge base of A
(or for a set, if any of the commits B through Z have that
property).

When we are going to check a series of commits A1 through An
to see whether each contains B (e.g., because we are
deciding which tags to show with "git tag --contains"), we
do a series of merge base calculations. This can be very
expensive, as we repeat a lot of traversal work.

Instead, let's leverage the fact that we are going to use
the same --contains list for each tag, and mark areas of the
commit graph is definitely containing those commits, or
definitely not containing those commits. Later tags can then
stop traversing as soon as they see a previously calculated
answer.

This sped up "git tag --contains HEAD~200" in the linux-2.6
repository from:

  real    0m15.417s
  user    0m15.197s
  sys     0m0.220s

to:

  real    0m5.329s
  user    0m5.144s
  sys     0m0.184s

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 builtin/tag.c |   46 +++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 45 insertions(+), 1 deletions(-)

diff --git a/builtin/tag.c b/builtin/tag.c
index ec926fc..575a03c 100644
--- a/builtin/tag.c
+++ b/builtin/tag.c
@@ -12,6 +12,8 @@
 #include "tag.h"
 #include "run-command.h"
 #include "parse-options.h"
+#include "diff.h"
+#include "revision.h"
 
 static const char * const git_tag_usage[] = {
 	"git tag [-a|-s|-u <key-id>] [-f] [-m <msg>|-F <file>] <tagname> [<head>]",
@@ -29,6 +31,48 @@ struct tag_filter {
 	struct commit_list *with_commit;
 };
 
+static int in_commit_list(const struct commit_list *want, struct commit *c)
+{
+	for (; want; want = want->next)
+		if (!hashcmp(want->item->object.sha1, c->object.sha1))
+			return 1;
+	return 0;
+}
+
+static int contains_recurse(struct commit *candidate,
+			    const struct commit_list *want)
+{
+	struct commit_list *p;
+
+	/* was it previously marked as containing a want commit? */
+	if (candidate->object.flags & TMP_MARK)
+		return 1;
+	/* or marked as not possibly containing a want commit? */
+	if (candidate->object.flags & UNINTERESTING)
+		return 0;
+	/* or are we it? */
+	if (in_commit_list(want, candidate))
+		return 1;
+
+	if (parse_commit(candidate) < 0)
+		return 0;
+
+	/* Otherwise recurse and mark ourselves for future traversals. */
+	for (p = candidate->parents; p; p = p->next) {
+		if (contains_recurse(p->item, want)) {
+			candidate->object.flags |= TMP_MARK;
+			return 1;
+		}
+	}
+	candidate->object.flags |= UNINTERESTING;
+	return 0;
+}
+
+int contains(struct commit *candidate, const struct commit_list *want)
+{
+	return contains_recurse(candidate, want);
+}
+
 static int show_reference(const char *refname, const unsigned char *sha1,
 			  int flag, void *cb_data)
 {
@@ -47,7 +91,7 @@ static int show_reference(const char *refname, const unsigned char *sha1,
 			commit = lookup_commit_reference_gently(sha1, 1);
 			if (!commit)
 				return 0;
-			if (!is_descendant_of(commit, filter->with_commit))
+			if (!contains(commit, filter->with_commit))
 				return 0;
 		}
 
-- 
1.7.5.3

  reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-11 19:04 [PATCH 0/4] Speed up git tag --contains Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` Ævar Arnfjörð Bjarmason [this message]
2011-06-11 19:04 ` [PATCH 2/4] limit "contains" traversals based on commit timestamp Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 3/4] default core.clockskew variable to one day Ævar Arnfjörð Bjarmason
2011-06-11 19:04 ` [PATCH 4/4] Why is "git tag --contains" so slow? Ævar Arnfjörð Bjarmason
2011-07-06  6:40 ` [PATCH 0/4] Speed up git tag --contains Jeff King
2011-07-06  6:54   ` Jeff King
2011-07-06 19:06     ` Clemens Buchacher
2011-07-06  6:56   ` Jonathan Nieder
2011-07-06  7:03     ` Jeff King
2011-07-06 14:26       ` generation numbers (was: [PATCH 0/4] Speed up git tag --contains) Jakub Narebski
2011-07-06 15:01         ` Ted Ts'o
2011-07-06 18:12           ` Jeff King
2011-07-06 18:46             ` Jakub Narebski
2011-07-07 18:59               ` Jeff King
2011-07-07 19:34                 ` generation numbers Junio C Hamano
2011-07-07 20:31                   ` Jakub Narebski
2011-07-07 20:52                     ` A Large Angry SCM
2011-07-08  0:29                       ` Junio C Hamano
2011-07-08 22:57                   ` Jeff King
2011-07-06 23:22             ` Junio C Hamano
2011-07-07 19:08               ` Jeff King
2011-07-07 20:10                 ` Jakub Narebski
2018-01-12 18:56   ` [PATCH 0/4] Speed up git tag --contains csilvers
2018-03-03  5:15     ` Jeff King
2018-03-08 23:05       ` csilvers
2018-03-12 13:45       ` Derrick Stolee
2018-03-12 23:59         ` Jeff King

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: http://vger.kernel.org/majordomo-info.html

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1307819051-25748-2-git-send-email-avarab@gmail.com \
    --to=avarab@gmail.com \
    --cc=git@vger.kernel.org \
    --cc=gitster@pobox.com \
    --cc=peff@peff.net \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

git@vger.kernel.org mailing list mirror (one of many)

Archives are clonable:
	git clone --mirror https://public-inbox.org/git
	git clone --mirror http://ou63pmih66umazou.onion/git
	git clone --mirror http://czquwvybam4bgbro.onion/git
	git clone --mirror http://hjrcffqmbrq6wope.onion/git

Newsgroups are available over NNTP:
	nntp://news.public-inbox.org/inbox.comp.version-control.git
	nntp://ou63pmih66umazou.onion/inbox.comp.version-control.git
	nntp://czquwvybam4bgbro.onion/inbox.comp.version-control.git
	nntp://hjrcffqmbrq6wope.onion/inbox.comp.version-control.git
	nntp://news.gmane.org/gmane.comp.version-control.git

 note: .onion URLs require Tor: https://www.torproject.org/
       or Tor2web: https://www.tor2web.org/

AGPL code for this site: git clone https://public-inbox.org/ public-inbox