t/perf: implement performace tests for pseudo-merge bitmapsNotice: this object is not reachable from any branch.

Implement a straightforward performance test demonstrating the benefit
of pseudo-merge bitmaps by measuring how long it takes to count
reachable objects in a few different scenarios:

  - without bitmaps, to demonstrate a reasonable baseline
  - with bitmaps, but without pseudo-merges
  - with bitmaps and pseudo-merges

Results from running this test on git.git are as follows:

    Test                                                                this tree
    -----------------------------------------------------------------------------------
    5333.2: git rev-list --count --all --objects (no bitmaps)           3.46(3.37+0.09)
    5333.3: git rev-list --count --all --objects (no pseudo-merges)     0.13(0.11+0.01)
    5333.4: git rev-list --count --all --objects (with pseudo-merges)   0.12(0.11+0.01)

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Notice: this object is not reachable from any branch.

1 files changed, 32 insertions, 0 deletions

diff --git a/t/perf/p5333-pseudo-merge-bitmaps.sh b/t/perf/p5333-pseudo-merge-bitmaps.sh
new file mode 100755
index 0000000000..4bec409d10
--- /dev/null
+++ b/t/perf/p5333-pseudo-merge-bitmaps.sh
@@ -0,0 +1,32 @@
+#!/bin/sh
+
+test_description='pseudo-merge bitmaps'
+. ./perf-lib.sh
+
+test_perf_large_repo
+
+test_expect_success 'setup' '
+	git \
+		-c bitmapPseudoMerge.all.pattern="refs/" \
+		-c bitmapPseudoMerge.all.threshold=now \
+		-c bitmapPseudoMerge.all.stableThreshold=never \
+		-c bitmapPseudoMerge.all.maxMerges=64 \
+		-c pack.writeBitmapLookupTable=true \
+		repack -adb
+'
+
+test_perf 'git rev-list --count --all --objects (no bitmaps)' '
+	git rev-list --objects --all
+'
+
+test_perf 'git rev-list --count --all --objects (no pseudo-merges)' '
+	GIT_TEST_USE_PSEDUO_MERGES=0 \
+		git rev-list --objects --all --use-bitmap-index
+'
+
+test_perf 'git rev-list --count --all --objects (with pseudo-merges)' '
+	GIT_TEST_USE_PSEDUO_MERGES=1 \
+		git rev-list --objects --all --use-bitmap-index
+'
+
+test_done