[10/15] refs/packed-backend.c: add trace2 counters for skip list

Commit Message

Taylor Blau May 8, 2023, 10 p.m. UTC

The previous commit added low-level tests to ensure that the packed-refs
iterator did not enumerate excluded sections of the refspace.

However, there was no guarantee that these sections weren't being
visited, only that they were being suppressed from the output. To harden
these tests, add a trace2 counter which tracks the number of regions
skipped by the packed-refs iterator, and assert on its value.

Suggested-by: Derrick Stolee <[e-mail]>
Signed-off-by: Taylor Blau <[e-mail]>
---
 refs/packed-backend.c   |  2 ++
 t/t1419-exclude-refs.sh | 54 ++++++++++++++++++++++++++++-------------
 trace2.h                |  2 ++
 trace2/tr2_ctr.c        |  5 ++++
 4 files changed, 46 insertions(+), 17 deletions(-)

Patch

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index 137a4233f6..ddfa9add14 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -11,6 +11,7 @@ 
 #include "../chdir-notify.h"
 #include "../wrapper.h"
 #include "../write-or-die.h"
+#include "../trace2.h"
 
 enum mmap_strategy {
 	/*
@@ -844,6 +845,7 @@  static int next_record(struct packed_ref_iterator *iter)
 		iter->skip_pos++;
 		if (iter->pos < curr->end) {
 			iter->pos = curr->end;
+			trace2_counter_add(TRACE2_COUNTER_ID_PACKED_REFS_SKIPS, 1);
 			break;
 		}
 	}
diff --git a/t/t1419-exclude-refs.sh b/t/t1419-exclude-refs.sh
index da5265a5a8..051b5a54ce 100755
--- a/t/t1419-exclude-refs.sh
+++ b/t/t1419-exclude-refs.sh
@@ -9,7 +9,8 @@  TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 for_each_ref__exclude () {
-	test-tool ref-store main for-each-ref--exclude "$@" >actual.raw
+	GIT_TRACE2_PERF=1 test-tool ref-store main \
+		for-each-ref--exclude "$@" >actual.raw
 	cut -d ' ' -f 2 actual.raw
 }
 
@@ -17,6 +18,17 @@  for_each_ref () {
 	git for-each-ref --format='%(refname)' "$@"
 }
 
+assert_skips () {
+	local nr="$1"
+	local trace="$2"
+
+	grep -q "name:skips_made value:$nr" $trace
+}
+
+assert_no_skips () {
+	! assert_skips ".*" "$1"
+}
+
 test_expect_success 'setup' '
 	test_commit --no-tag base &&
 	base="$(git rev-parse HEAD)" &&
@@ -36,66 +48,74 @@  test_expect_success 'setup' '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/foo/)' '
 	# region in middle
-	for_each_ref__exclude refs/heads refs/heads/foo >actual &&
+	for_each_ref__exclude refs/heads refs/heads/foo >actual 2>perf &&
 	for_each_ref refs/heads/bar refs/heads/baz refs/heads/quux >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_skips 1 perf
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/bar/)' '
 	# region at beginning
-	for_each_ref__exclude refs/heads refs/heads/bar >actual &&
+	for_each_ref__exclude refs/heads refs/heads/bar >actual 2>perf &&
 	for_each_ref refs/heads/baz refs/heads/foo refs/heads/quux >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_skips 1 perf
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/quux/)' '
 	# region at end
-	for_each_ref__exclude refs/heads refs/heads/quux >actual &&
+	for_each_ref__exclude refs/heads refs/heads/quux >actual 2>perf &&
 	for_each_ref refs/heads/foo refs/heads/bar refs/heads/baz >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_skips 1 perf
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/bar/, refs/heads/quux/)' '
 	# disjoint regions
-	for_each_ref__exclude refs/heads refs/heads/bar refs/heads/quux >actual &&
+	for_each_ref__exclude refs/heads refs/heads/bar refs/heads/quux >actual 2>perf &&
 	for_each_ref refs/heads/baz refs/heads/foo >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_skips 2 perf
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/bar/, refs/heads/baz/)' '
 	# adjacent, non-overlapping regions
-	for_each_ref__exclude refs/heads refs/heads/bar refs/heads/baz >actual &&
+	for_each_ref__exclude refs/heads refs/heads/bar refs/heads/baz >actual 2>perf &&
 	for_each_ref refs/heads/foo refs/heads/quux >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_skips 1 perf
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/ba refs/heads/baz/)' '
 	# overlapping region
-	for_each_ref__exclude refs/heads refs/heads/ba refs/heads/baz >actual &&
+	for_each_ref__exclude refs/heads refs/heads/ba refs/heads/baz >actual 2>perf &&
 	for_each_ref refs/heads/foo refs/heads/quux >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_skips 1 perf
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/does/not/exist)' '
 	# empty region
-	for_each_ref__exclude refs/heads refs/heads/does/not/exist >actual &&
+	for_each_ref__exclude refs/heads refs/heads/does/not/exist >actual 2>perf &&
 	for_each_ref >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_no_skips
 '
 
 test_expect_success 'for_each_ref__exclude(refs/heads/ba*)' '
 	# discards meta-characters
-	for_each_ref__exclude refs/heads "refs/heads/ba*" >actual &&
+	for_each_ref__exclude refs/heads "refs/heads/ba*" >actual 2>perf &&
 	for_each_ref >expect &&
 
-	test_cmp expect actual
+	test_cmp expect actual &&
+	assert_no_skips
 '
 
 test_done
diff --git a/trace2.h b/trace2.h
index 4ced30c0db..6a116f60a9 100644
--- a/trace2.h
+++ b/trace2.h
@@ -551,6 +551,8 @@  enum trace2_counter_id {
 	TRACE2_COUNTER_ID_TEST1 = 0, /* emits summary event only */
 	TRACE2_COUNTER_ID_TEST2,     /* emits summary and thread events */
 
+	TRACE2_COUNTER_ID_PACKED_REFS_SKIPS, /* counts number of skips */
+
 	/* Add additional counter definitions before here. */
 	TRACE2_NUMBER_OF_COUNTERS
 };
diff --git a/trace2/tr2_ctr.c b/trace2/tr2_ctr.c
index b342d3b1a3..f7efbc7646 100644
--- a/trace2/tr2_ctr.c
+++ b/trace2/tr2_ctr.c
@@ -27,6 +27,11 @@  static struct tr2_counter_metadata tr2_counter_metadata[TRACE2_NUMBER_OF_COUNTER
 		.name = "test2",
 		.want_per_thread_events = 1,
 	},
+	[TRACE2_COUNTER_ID_PACKED_REFS_SKIPS] = {
+		.category = "packed-refs",
+		.name = "skips_made",
+		.want_per_thread_events = 0,
+	},
 
 	/* Add additional metadata before here. */
 };