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send-pack.c: add config push.useBitmaps

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Reachability bitmaps are designed to speed up the "counting objects"
phase of generating a pack during a clone or fetch. They are not
optimized for Git clients sending a small topic branch via "git push".
In some cases (see [1]), using reachability bitmaps during "git push"
can cause significant performance regressions.

Add a new "push.useBitmaps" configuration variable to allow users to
tell "git push" not to use bitmaps. We already have "pack.bitmaps"
that controls the use of bitmaps, but a separate configuration variable
allows the reachability bitmaps to still be used in other areas,
such as "git upload-pack", while disabling it only for "git push".

[1]: https://lore.kernel.org/git/87zhoz8b9o.fsf@evledraar.gmail.com/

Signed-off-by: Kyle Zhao <kylezhao@tencent.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Kyle Zhao 2022-06-17 19:06:19 +00:00 committed by Junio C Hamano
parent 8168d5e9c2
commit 82f67ee13f
4 changed files with 35 additions and 1 deletions
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5
Documentation/config/push.txt
View File

@ -137,3 +137,8 @@ push.negotiate::
server attempt to find commits in common. If "false", Git will
rely solely on the server's ref advertisement to find commits
in common.
push.useBitmaps::
If set to "false", disable use of bitmaps for "git push" even if
`pack.useBitmaps` is "true", without preventing other git operations
from using bitmaps. Default is true.

6
send-pack.c
View File

@ -84,6 +84,8 @@ static int pack_objects(int fd, struct ref *refs, struct oid_array *advertised,
strvec_push(&po.args, "--progress");
if (is_repository_shallow(the_repository))
strvec_push(&po.args, "--shallow");
if (args->disable_bitmaps)
strvec_push(&po.args, "--no-use-bitmap-index");
po.in = -1;
po.out = args->stateless_rpc ? -1 : fd;
po.git_cmd = 1;
@ -487,6 +489,7 @@ int send_pack(struct send_pack_args *args,
struct async demux;
const char *push_cert_nonce = NULL;
struct packet_reader reader;
int use_bitmaps;
if (!remote_refs) {
fprintf(stderr, "No refs in common and none specified; doing nothing.\n"
@ -498,6 +501,9 @@ int send_pack(struct send_pack_args *args,
if (push_negotiate)
get_commons_through_negotiation(args->url, remote_refs, &commons);
if (!git_config_get_bool("push.usebitmaps", &use_bitmaps))
args->disable_bitmaps = !use_bitmaps;
git_config_get_bool("transfer.advertisesid", &advertise_sid);
/* Does the other end support the reporting? */

3
send-pack.h
View File

@ -26,7 +26,8 @@ struct send_pack_args {
/* One of the SEND_PACK_PUSH_CERT_* constants. */
push_cert:2,
stateless_rpc:1,
atomic:1;
atomic:1,
disable_bitmaps:1;
const struct string_list *push_options;
};

22
t/t5516-fetch-push.sh
View File

@ -1865,4 +1865,26 @@ test_expect_success 'push warns or fails when using username:password' '
test_line_count = 1 warnings
'
test_expect_success 'push with config push.useBitmaps' '
mk_test testrepo heads/main &&
git checkout main &&
test_unconfig push.useBitmaps &&
GIT_TRACE2_EVENT="$PWD/default" \
git push testrepo main:test &&
test_subcommand git pack-objects --all-progress-implied --revs --stdout \
--thin --delta-base-offset -q <default &&
test_config push.useBitmaps true &&
GIT_TRACE2_EVENT="$PWD/true" \
git push testrepo main:test2 &&
test_subcommand git pack-objects --all-progress-implied --revs --stdout \
--thin --delta-base-offset -q <true &&
test_config push.useBitmaps false &&
GIT_TRACE2_EVENT="$PWD/false" \
git push testrepo main:test3 &&
test_subcommand git pack-objects --all-progress-implied --revs --stdout \
--thin --delta-base-offset -q --no-use-bitmap-index <false
'
test_done