[v4,24/24] t/perf: implement performance tests for pseudo-merge bitmaps

Commit Message

Taylor Blau May 23, 2024, 9:27 p.m. UTC

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)           3.54(3.45+0.08)
    5333.3: git rev-list --count --all --objects (no pseudo-merges)     0.43(0.40+0.03)
    5333.4: git rev-list --count --all --objects (with pseudo-merges)   0.12(0.11+0.01)

On a private repository which is much larger, and has many spikey parts
of history that aren't merged into the 'master' branch, the results are
as follows:

    Test                                                                this tree
    ---------------------------------------------------------------------------------------
    5333.1: git rev-list --count --all --objects (no bitmaps)           122.29(121.31+0.97)
    5333.2: git rev-list --count --all --objects (no pseudo-merges)     21.88(21.30+0.58)
    5333.3: git rev-list --count --all --objects (with pseudo-merges)   5.05(4.77+0.28)

Signed-off-by: Taylor Blau <[e-mail]>
---
 t/perf/p5333-pseudo-merge-bitmaps.sh | 32 ++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)
 create mode 100755 t/perf/p5333-pseudo-merge-bitmaps.sh

Patch

diff --git a/t/perf/p5333-pseudo-merge-bitmaps.sh b/t/perf/p5333-pseudo-merge-bitmaps.sh
new file mode 100755
index 00000000000..2e8b1d2635e
--- /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_PSEUDO_MERGES=0 \
+		git rev-list --objects --all --use-bitmap-index
+'
+
+test_perf 'git rev-list --count --all --objects (with pseudo-merges)' '
+	GIT_TEST_USE_PSEUDO_MERGES=1 \
+		git rev-list --objects --all --use-bitmap-index
+'
+
+test_done