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From: Jeff King <peff@peff.net>
To: "Ævar Arnfjörð Bjarmason" <avarab@gmail.com>
Cc: Stefan Beller <sbeller@google.com>,
	git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: [PATCH 2/4] t5310: test delta reuse with bitmaps
Date: Sat, 1 Sep 2018 03:48:13 -0400	[thread overview]
Message-ID: <20180901074813.GB25461@sigill.intra.peff.net> (raw)
In-Reply-To: <20180901074145.GA24023@sigill.intra.peff.net>

Commit 6a1e32d532 (pack-objects: reuse on-disk deltas for
thin "have" objects, 2018-08-21) taught pack-objects a new
optimization trick. Since this wasn't meant to change
user-visible behavior, but only produce smaller packs more
quickly, testing focused on t/perf/p5311.

However, since people don't run perf tests very often, we
should make sure that the feature is exercised in the
regular test suite. This patch does so.

Signed-off-by: Jeff King <peff@peff.net>
---
Side note: If we do squash patch 1 into the eariler series, that will
invalidate the commit id mentioned in the commit message here.

 t/t5310-pack-bitmaps.sh | 93 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)

diff --git a/t/t5310-pack-bitmaps.sh b/t/t5310-pack-bitmaps.sh
index 557bd0d0c0..af38776054 100755
--- a/t/t5310-pack-bitmaps.sh
+++ b/t/t5310-pack-bitmaps.sh
@@ -342,4 +342,97 @@ test_expect_success 'truncated bitmap fails gracefully' '
 	test_i18ngrep corrupt stderr
 '
 
+# have_delta <obj> <expected_base>
+#
+# Note that because this relies on cat-file, it might find _any_ copy of an
+# object in the repository. The caller is responsible for making sure
+# there's only one (e.g., via "repack -ad", or having just fetched a copy).
+have_delta () {
+	echo $2 >expect &&
+	echo $1 | git cat-file --batch-check="%(deltabase)" >actual &&
+	test_cmp expect actual
+}
+
+# Create a state of history with these properties:
+#
+#  - refs that allow a client to fetch some new history, while sharing some old
+#    history with the server; we use branches delta-reuse-old and
+#    delta-reuse-new here
+#
+#  - the new history contains an object that is stored on the server as a delta
+#    against a base that is in the old history
+#
+#  - the base object is not immediately reachable from the tip of the old
+#    history; finding it would involve digging down through history we know the
+#    other side has
+#
+# This should result in a state where fetching from old->new would not
+# traditionally reuse the on-disk delta (because we'd have to dig to realize
+# that the client has it), but we will do so if bitmaps can tell us cheaply
+# that the other side has it.
+test_expect_success 'set up thin delta-reuse parent' '
+	# This first commit contains the buried base object.
+	test-tool genrandom delta 16384 >file &&
+	git add file &&
+	git commit -m "delta base" &&
+	base=$(git rev-parse --verify HEAD:file) &&
+
+	# These intermediate commits bury the base back in history.
+	# This becomes the "old" state.
+	for i in 1 2 3 4 5
+	do
+		echo $i >file &&
+		git commit -am "intermediate $i" || return 1
+	done &&
+	git branch delta-reuse-old &&
+
+	# And now our new history has a delta against the buried base. Note
+	# that this must be smaller than the original file, since pack-objects
+	# prefers to create deltas from smaller objects to larger.
+	test-tool genrandom delta 16300 >file &&
+	git commit -am "delta result" &&
+	delta=$(git rev-parse --verify HEAD:file) &&
+	git branch delta-reuse-new &&
+
+	# Repack with bitmaps and double check that we have the expected delta
+	# relationship.
+	git repack -adb &&
+	have_delta $delta $base
+'
+
+# Now we can sanity-check the non-bitmap behavior (that the server is not able
+# to reuse the delta). This isn't strictly something we care about, so this
+# test could be scrapped in the future. But it makes sure that the next test is
+# actually triggering the feature we want.
+#
+# Note that our tools for working with on-the-wire "thin" packs are limited. So
+# we actually perform the fetch, retain the resulting pack, and inspect the
+# result.
+test_expect_success 'fetch without bitmaps ignores delta against old base' '
+	test_config pack.usebitmaps false &&
+	test_when_finished "rm -rf client.git" &&
+	git init --bare client.git &&
+	(
+		cd client.git &&
+		git config transfer.unpackLimit 1 &&
+		git fetch .. delta-reuse-old:delta-reuse-old &&
+		git fetch .. delta-reuse-new:delta-reuse-new &&
+		have_delta $delta $ZERO_OID
+	)
+'
+
+# And do the same for the bitmap case, where we do expect to find the delta.
+test_expect_success 'fetch with bitmaps can reuse old base' '
+	test_config pack.usebitmaps true &&
+	test_when_finished "rm -rf client.git" &&
+	git init --bare client.git &&
+	(
+		cd client.git &&
+		git config transfer.unpackLimit 1 &&
+		git fetch .. delta-reuse-old:delta-reuse-old &&
+		git fetch .. delta-reuse-new:delta-reuse-new &&
+		have_delta $delta $base
+	)
+'
+
 test_done
-- 
2.19.0.rc1.549.g6ce4dc0f08


  parent reply	other threads:[~2018-09-01  7:48 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-21 18:41 [PATCH] test-tool.h: include git-compat-util.h Jeff King
2018-08-21 19:03 ` Junio C Hamano
2018-08-21 19:06 ` [PATCH 1/6] t/perf: factor boilerplate out of test_perf Jeff King
2018-08-21 19:06 ` [PATCH 2/6] t/perf: factor out percent calculations Jeff King
2018-08-21 19:06 ` [PATCH 3/6] t/perf: add infrastructure for measuring sizes Jeff King
2018-08-22 13:40   ` Derrick Stolee
2018-08-22 15:31     ` Jeff King
2018-08-21 19:06 ` [PATCH 4/6] t/perf: add perf tests for fetches from a bitmapped server Jeff King
2018-08-21 19:07 ` [PATCH 5/6] pack-bitmap: save "have" bitmap from walk Jeff King
2018-08-21 19:47   ` Derrick Stolee
2018-08-21 19:54     ` Jeff King
2018-08-31 15:23   ` Ævar Arnfjörð Bjarmason
2018-08-31 22:55     ` Jeff King
2018-09-01  7:41       ` [PATCH 0/4] un-breaking pack-objects with bitmaps Jeff King
2018-09-01  7:44         ` [PATCH 1/4] bitmap_has_sha1_in_uninteresting(): drop BUG check Jeff King
2018-09-01  7:48         ` Jeff King [this message]
2018-09-01  8:03           ` [PATCH 2/4] t5310: test delta reuse with bitmaps Jeff King
2018-09-01 20:29             ` Ævar Arnfjörð Bjarmason
2018-09-01 22:46               ` Ben Peart
2018-09-02  5:51               ` Jeff King
2018-09-04 19:05             ` Stefan Beller
2018-09-04 19:45               ` Junio C Hamano
2018-09-04 20:02               ` Jeff King
2018-09-01  7:49         ` [PATCH 3/4] traverse_bitmap_commit_list(): don't free result Jeff King
2018-09-01  7:50         ` [PATCH 4/4] pack-bitmap: drop "loaded" flag Jeff King
2018-09-04 19:30         ` [PATCH 0/4] un-breaking pack-objects with bitmaps Stefan Beller
2018-09-04 20:03           ` Jeff King
2018-09-08  6:43         ` Ævar Arnfjörð Bjarmason
2018-09-10 16:53           ` Junio C Hamano
2018-09-10 18:48             ` Jeff King
2018-09-10 19:23               ` Junio C Hamano
2018-08-21 19:07 ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King
2018-08-21 19:43   ` Junio C Hamano
2018-08-21 19:50     ` Junio C Hamano
2018-08-21 20:07       ` Jeff King
2018-08-21 20:14         ` Jeff King
2018-08-21 20:52           ` Junio C Hamano
2018-08-21 21:30             ` Jeff King
2018-08-21 20:57         ` Junio C Hamano
2018-08-21 21:32           ` Jeff King
2018-08-23  0:43           ` [PATCH 0/9] trailer-parsing false positives Jeff King
2018-08-23  0:44             ` [PATCH 1/9] trailer: use size_t for string offsets Jeff King
2018-08-23  0:45             ` [PATCH 2/9] trailer: use size_t for iterating trailer list Jeff King
2018-08-23  0:46             ` [PATCH 3/9] trailer: pass process_trailer_opts to trailer_info_get() Jeff King
2018-08-23  0:48             ` [PATCH 4/9] interpret-trailers: tighten check for "---" patch boundary Jeff King
2018-08-23  0:49             ` [PATCH 5/9] interpret-trailers: allow suppressing "---" divider Jeff King
2018-08-23  0:50             ` [PATCH 6/9] pretty, ref-filter: format %(trailers) with no_divider option Jeff King
2018-08-23  0:50             ` [PATCH 7/9] sequencer: ignore "---" divider when parsing trailers Jeff King
2018-08-23  0:50             ` [PATCH 8/9] append_signoff: use size_t for string offsets Jeff King
2018-08-23  0:51             ` [PATCH 9/9] sequencer: handle ignore_footer when parsing trailers Jeff King
2018-08-23 18:30             ` [PATCH 0/9] trailer-parsing false positives Junio C Hamano
2018-08-24  7:26               ` Jeff King
2018-08-21 20:00     ` [PATCH 6/6] pack-objects: reuse on-disk deltas for thin "have" objects Jeff King

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