From: "Derrick Stolee via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Junio C Hamano <gitster@pobox.com>
Subject: [PATCH 0/1] send-pack: set core.warnAmbiguousRefs=false
Date: Tue, 06 Nov 2018 11:13:47 -0800 (PST) [thread overview]
Message-ID: <pull.68.git.gitgitgadget@gmail.com> (raw)
I've been looking into the performance of git push for very large repos. Our
users are reporting that 60-80% of git push time is spent during the
"Enumerating objects" phase of git pack-objects.
A git push process runs several processes during its run, but one includes
git send-pack which calls git pack-objects and passes the known have/wants
into stdin using object ids. However, the default setting for
core.warnAmbiguousRefs requires git pack-objects to check for ref names
matching the ref_rev_parse_rules array in refs.c. This means that every
object is triggering at least six "file exists?" queries.
When there are a lot of refs, this can add up significantly! My PerfView
trace for a simple push measured 3 seconds spent checking these paths.
The fix for this is simple: set core.warnAmbiguousRefs to false for this
specific call of git pack-objects coming from git send-pack. We don't want
to default it to false for all calls to git pack-objects, as it is valid to
pass ref names instead of object ids. This helps regain these seconds during
a push.
In addition to this patch submission, we are looking into merging it into
our fork sooner [1].
[1] https://github.com/Microsoft/git/pull/67
Derrick Stolee (1):
send-pack: set core.warnAmbiguousRefs=false
send-pack.c | 2 ++
1 file changed, 2 insertions(+)
base-commit: cae598d9980661a978e2df4fb338518f7bf09572
Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-68%2Fderrickstolee%2Fsend-pack-config-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-68/derrickstolee/send-pack-config-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/68
--
gitgitgadget
next reply other threads:[~2018-11-06 19:13 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-06 19:13 Derrick Stolee via GitGitGadget [this message]
2018-11-06 19:13 ` [PATCH 1/1] send-pack: set core.warnAmbiguousRefs=false Derrick Stolee via GitGitGadget
2018-11-06 19:44 ` [PATCH 0/1] " Jeff King
2018-11-06 19:51 ` Jeff King
2018-11-06 20:16 ` Derrick Stolee
2018-11-06 20:00 ` Derrick Stolee
2018-11-06 20:34 ` [PATCH v2 " Derrick Stolee via GitGitGadget
2018-11-06 20:34 ` [PATCH v2 1/1] pack-objects: ignore ambiguous object warnings Derrick Stolee via GitGitGadget
2018-11-06 21:12 ` Jeff King
2018-11-07 1:54 ` Junio C Hamano
2018-11-07 8:52 ` Junio C Hamano
2018-11-07 9:21 ` Jeff King
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