From: Taylor Blau <me@ttaylorr.com>
To: git@vger.kernel.org
Cc: peff@peff.net, dstolee@microsoft.com
Subject: [PATCH 1/1] commit-graph.c: avoid unnecessary tag dereference when merging
Date: Fri, 20 Mar 2020 21:44:23 -0600 [thread overview]
Message-ID: <4c79a9ea909ebff8c0987bcf95692da92e79bda4.1584762087.git.me@ttaylorr.com> (raw)
In-Reply-To: <cover.1584762087.git.me@ttaylorr.com>
When performing a 'git commit-graph write' with '--split', the
commit-graph machinery calls 'merge_commit_graph()' after deciding on a
split strategy to optionally clean up any existing commit-graph
layers that were made obsolete by the split strategy [1].
At this time, 'merge_commit_graph()' checks each commit that it writes
into the merged graph to make sure that it still exists in the object
store.
To do this, it uses 'lookup_commit_reference_gently()', which accepts
either a commit object, or a tag that refers to a commit. However, since
all 'oid' arguments passed to this function are from within the
commit-graphs being merged, we never pass a commit reference, and so any
time we spend in 'deref_tag()' is wasted.
Improve the situation by using 'repo_has_object_file' to check if the
object still exists, and '{lookup,repo_parse}_commit()' to turn it into
a bona-fide 'struct commit *'.
In my testing environment, this improves the time to "merge" a split
commit-graph containing all reachable commits in the kernel by
re-writing the same commit-graph (effectively measuring the time it
takes to check that all of those commits still exist) from:
Attempt 1: 9.614
Attempt 2: 10.984
Attempt 3: 10.39
Attempt 4: 9.14
Attempt 5: 9.439
real 0m9.140s
user 0m8.207s
sys 0m0.602s
to:
Attempt 1: 9.12
Attempt 2: 8.904
Attempt 3: 9.361
Attempt 4: 9.288
Attempt 5: 9.677
real 0m8.904s
user 0m8.208s
sys 0m0.596s
yielding a modest ~2.6% improvement in the best timings from each run,
and ~7.4% improvement on average.
[1]: This can happen if, for example, the new commit-graph exceeds the
maximum allowed factor on the number of commits.
Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
commit-graph.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/commit-graph.c b/commit-graph.c
index f013a84e29..c7cfadc786 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -1599,14 +1599,18 @@ static void merge_commit_graph(struct write_commit_graph_context *ctx,
for (i = 0; i < g->num_commits; i++) {
struct object_id oid;
- struct commit *result;
+ struct commit *result = NULL;
display_progress(ctx->progress, i + 1);
load_oid_from_graph(g, i + offset, &oid);
/* only add commits if they still exist in the repo */
- result = lookup_commit_reference_gently(ctx->r, &oid, 1);
+ if (repo_has_object_file(ctx->r, &oid)) {
+ result = lookup_commit(ctx->r, &oid);
+ if (repo_parse_commit(ctx->r, result))
+ result = NULL;
+ }
if (result) {
ctx->commits.list[ctx->commits.nr] = result;
--
2.26.0.rc2.311.g8e52d2684b
next prev parent reply other threads:[~2020-03-21 3:48 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-21 3:44 [PATCH 0/1] commit-graph: avoid unnecessary tag deference when merging Taylor Blau
2020-03-21 3:44 ` Taylor Blau [this message]
2020-03-21 5:00 ` [PATCH 1/1] commit-graph.c: avoid unnecessary tag dereference " Jeff King
2020-03-21 6:11 ` Taylor Blau
2020-03-21 6:24 ` Taylor Blau
2020-03-21 7:03 ` Jeff King
2020-03-21 17:27 ` Taylor Blau
2020-03-22 5:36 ` Jeff King
2020-03-22 11:04 ` SZEDER Gábor
2020-03-22 18:45 ` looking up object types quickly, was " Jeff King
2020-03-22 19:18 ` Jeff King
2020-03-23 20:15 ` Taylor Blau
2020-03-22 16:45 ` Taylor Blau
2020-03-24 6:06 ` Jeff King
2020-03-21 18:50 ` Junio C Hamano
2020-03-22 0:03 ` Derrick Stolee
2020-03-22 0:20 ` Taylor Blau
2020-03-22 0:23 ` Derrick Stolee
2020-03-22 5:49 ` Jeff King
2020-03-22 6:04 ` Jeff King
2020-03-22 15:47 ` Taylor Blau
2020-03-24 6:11 ` Jeff King
2020-03-24 23:08 ` Taylor Blau
2020-03-27 8:42 ` Jeff King
2020-03-27 15:03 ` Taylor Blau
2020-03-22 15:44 ` Taylor Blau
2020-03-24 6:14 ` Jeff King
2020-03-21 5:01 ` Junio C Hamano
2020-03-21 4:56 ` [PATCH 0/1] commit-graph: avoid unnecessary tag deference " Junio C Hamano
2020-03-21 5:04 ` Jeff King
2020-03-21 6:12 ` Taylor Blau
Reply instructions:
You may reply publicly 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=4c79a9ea909ebff8c0987bcf95692da92e79bda4.1584762087.git.me@ttaylorr.com \
--to=me@ttaylorr.com \
--cc=dstolee@microsoft.com \
--cc=git@vger.kernel.org \
--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
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).