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[PATCH 7/8] receive-pack: skip connectivity checks on delete-only commands

From
Patrick Steinhardt <ps@pks.im>
Date
May 19, 2021, 19:13 UTC
Message-ID
<68c60aff0c77c562aba5613ccbb9ab33ad8e0e08.1621451532.git.ps@pks.im>
In-Reply-To
<cover.1621451532.git.ps@pks.im>

In the case where git-receive-pack(1) receives only commands which delete references, then per technical specification the client MUST NOT send a packfile. As a result, we know that no new objects have been received, which makes it a moot point to check whether all received objects are fully connected.

Fix this by not doing a connectivity check in case there were no pushed objects. Given that git-rev-walk(1) with only negative references will not do any graph walk, no performance improvements are to be expected. Conceptionally, it is still the right thing to do though.

The following tests were executed on linux.git and back up above expectation:

Test v2.32.0-rc0 HEAD -------------------------------------------------------------------------------------------- 5400.3: receive-pack clone create 1.27(1.11+0.16) 1.26(1.12+0.14) -0.8% 5400.5: receive-pack clone update 1.27(1.13+0.13) 1.27(1.11+0.16) +0.0% 5400.7: receive-pack clone reset 0.13(0.11+0.02) 0.14(0.11+0.02) +7.7% 5400.9: receive-pack clone delete 0.02(0.01+0.01) 0.02(0.00+0.01) +0.0% 5400.11: receive-pack extrarefs create 33.01(18.80+14.43) 32.63(18.52+14.24) -1.2% 5400.13: receive-pack extrarefs update 33.13(18.85+14.50) 32.82(18.85+14.29) -0.9% 5400.15: receive-pack extrarefs reset 32.90(18.82+14.32) 32.70(18.76+14.20) -0.6% 5400.17: receive-pack extrarefs delete 9.13(4.35+4.77) 8.99(4.28+4.70) -1.5% 5400.19: receive-pack empty create 223.35(640.63+127.74) 226.96(655.16+131.93) +1.6%

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 builtin/receive-pack.c | 49 ++++++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 19 deletions(-)
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index a34742513a..b9263cec15 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1918,11 +1918,8 @@ static void execute_commands(struct command *commands,
 			     struct shallow_info *si,
 			     const struct string_list *push_options)
 {
-	struct check_connected_options opt = CHECK_CONNECTED_INIT;
 	struct command *cmd;
 	struct iterate_data data;
-	struct async muxer;
-	int err_fd = 0;
 	int run_proc_receive = 0;
 
 	if (unpacker_error) {
@@ -1931,25 +1928,39 @@ static void execute_commands(struct command *commands,
 		return;
 	}
 
-	if (use_sideband) {
-		memset(&muxer, 0, sizeof(muxer));
-		muxer.proc = copy_to_sideband;
-		muxer.in = -1;
-		if (!start_async(&muxer))
-			err_fd = muxer.in;
-		/* ...else, continue without relaying sideband */
-	}
-
 	data.cmds = commands;
 	data.si = si;
-	opt.err_fd = err_fd;
-	opt.progress = err_fd && !quiet;
-	opt.env = tmp_objdir_env(tmp_objdir);
-	if (check_connected(iterate_receive_command_list, &data, &opt))
-		set_connectivity_errors(commands, si);
 
-	if (use_sideband)
-		finish_async(&muxer);
+	/*
+	 * If received commands only consist of deletions, then the client MUST
+	 * NOT send a packfile because there cannot be any new objects in the
+	 * first place. As a result, we do not set up a quarantine environment
+	 * because we know no new objects will be received. And that in turn
+	 * means that we can skip connectivity checks here.
+	 */
+	if (tmp_objdir) {
+		struct check_connected_options opt = CHECK_CONNECTED_INIT;
+		struct async muxer;
+		int err_fd = 0;
+
+		if (use_sideband) {
+			memset(&muxer, 0, sizeof(muxer));
+			muxer.proc = copy_to_sideband;
+			muxer.in = -1;
+			if (!start_async(&muxer))
+				err_fd = muxer.in;
+			/* ...else, continue without relaying sideband */
+		}
+
+		opt.err_fd = err_fd;
+		opt.progress = err_fd && !quiet;
+		opt.env = tmp_objdir_env(tmp_objdir);
+		if (check_connected(iterate_receive_command_list, &data, &opt))
+			set_connectivity_errors(commands, si);
+
+		if (use_sideband)
+			finish_async(&muxer);
+	}
 
 	reject_updates_to_hidden(commands);
 
-- 
2.31.1
Previous: Patrick SteinhardtNext: Felipe Contreras
Message 13 of 22 in “Speed up connectivity checks via quarantine dir”
  1. 0/8 Speed up connectivity checks via quarantine dirPatrick Steinhardt, May 19, 2021
  2. 1/8 perf: fix when running with TEST_OUTPUT_DIRECTORYPatrick Steinhardt, May 19, 2021
  3. Chris TorekMay 20, 2021
  4. 2/8 p5400: add perf tests for git-receive-pack(1)Patrick Steinhardt, May 19, 2021
  5. Chris TorekMay 20, 2021
  6. Jeff KingMay 20, 2021
  7. SZEDER GáborMay 21, 2021
  8. 3/8 tmp-objdir: expose function to retrieve pathPatrick Steinhardt, May 19, 2021
  9. Elijah NewrenMay 20, 2021
  10. 4/8 packfile: have `for_each_file_in_pack_dir()` return error codesPatrick Steinhardt, May 19, 2021
  11. 5/8 object-file: allow reading loose objects without reading their contentsPatrick Steinhardt, May 19, 2021
  12. 6/8 connected: implement connectivity check via temporary object dirsPatrick Steinhardt, May 19, 2021
  13. 7/8 receive-pack: skip connectivity checks on delete-only commandsPatrick Steinhardt, May 19, 2021
  14. Felipe ContrerasMay 21, 2021
  15. Jeff KingMay 27, 2021
  16. 8/8 receive-pack: check connectivity via quarantined objectsPatrick Steinhardt, May 19, 2021
  17. Chris TorekMay 20, 2021
  18. Jeff KingMay 20, 2021
  19. Junio C HamanoMay 20, 2021
  20. Jeff KingMay 21, 2021
  21. Patrick SteinhardtMay 21, 2021
  22. Ævar Arnfjörð BjarmasonMay 21, 2021

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