DfsBlockCache: refactor stats implementations.

The stats interface has an implementation in the interface itself and another inside the PackExtBlockCache class. This asymmetry gets on the way to implement stats-per-table later.

Make DfsBlockCacheStats (the stats of a single table) a top-level class and create an aggregator class to combine multiple stats. This makes the stats classes mirror the table classes structure (singles tables + composite).

This change is part of a refactor to support providing detailed stats
breakdowns for cache implementations using multiple table instances
while keeping the existing "aggregated" view of cache stats.

Change-Id: I79c11e4ea24afe4b449efdbb47bc81eed363ffd3

2 files changed, 215 insertions, 1 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/AggregatedBlockCacheStatsTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/AggregatedBlockCacheStatsTest.java
new file mode 100644
index 0000000000..ac769498e2
--- /dev/null
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/AggregatedBlockCacheStatsTest.java
@@ -0,0 +1,215 @@
+/*
+ * Copyright (c) 2024, Google LLC and others
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Distribution License v. 1.0 which is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+package org.eclipse.jgit.internal.storage.dfs;
+
+import static org.eclipse.jgit.internal.storage.dfs.DfsBlockCacheTable.BlockCacheStats;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertArrayEquals;
+
+import java.util.List;
+
+import org.eclipse.jgit.internal.storage.pack.PackExt;
+import org.junit.Test;
+
+public class AggregatedBlockCacheStatsTest {
+	@Test
+	public void getName() {
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("name", List.of());
+
+		assertThat(aggregatedBlockCacheStats.getName(), equalTo("name"));
+	}
+
+	@Test
+	public void getCurrentSize_aggregatesCurrentSizes() {
+		long[] currentSizes = createEmptyStatsArray();
+
+		DfsBlockCacheStats packStats = new DfsBlockCacheStats();
+		packStats.addToLiveBytes(new TestKey(PackExt.PACK), 5);
+		currentSizes[PackExt.PACK.getPosition()] = 5;
+
+		DfsBlockCacheStats bitmapStats = new DfsBlockCacheStats();
+		bitmapStats.addToLiveBytes(new TestKey(PackExt.BITMAP_INDEX), 6);
+		currentSizes[PackExt.BITMAP_INDEX.getPosition()] = 6;
+
+		DfsBlockCacheStats indexStats = new DfsBlockCacheStats();
+		indexStats.addToLiveBytes(new TestKey(PackExt.INDEX), 7);
+		currentSizes[PackExt.INDEX.getPosition()] = 7;
+
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("name",
+						List.of(packStats, bitmapStats, indexStats));
+
+		assertArrayEquals(aggregatedBlockCacheStats.getCurrentSize(),
+				currentSizes);
+	}
+
+	@Test
+	public void getHitCount_aggregatesHitCounts() {
+		long[] hitCounts = createEmptyStatsArray();
+
+		DfsBlockCacheStats packStats = new DfsBlockCacheStats();
+		incrementCounter(5,
+				() -> packStats.incrementHit(new TestKey(PackExt.PACK)));
+		hitCounts[PackExt.PACK.getPosition()] = 5;
+
+		DfsBlockCacheStats bitmapStats = new DfsBlockCacheStats();
+		incrementCounter(6, () -> bitmapStats
+				.incrementHit(new TestKey(PackExt.BITMAP_INDEX)));
+		hitCounts[PackExt.BITMAP_INDEX.getPosition()] = 6;
+
+		DfsBlockCacheStats indexStats = new DfsBlockCacheStats();
+		incrementCounter(7,
+				() -> indexStats.incrementHit(new TestKey(PackExt.INDEX)));
+		hitCounts[PackExt.INDEX.getPosition()] = 7;
+
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("name",
+						List.of(packStats, bitmapStats, indexStats));
+
+		assertArrayEquals(aggregatedBlockCacheStats.getHitCount(), hitCounts);
+	}
+
+	@Test
+	public void getMissCount_aggregatesMissCounts() {
+		long[] missCounts = createEmptyStatsArray();
+
+		DfsBlockCacheStats packStats = new DfsBlockCacheStats();
+		incrementCounter(5,
+				() -> packStats.incrementMiss(new TestKey(PackExt.PACK)));
+		missCounts[PackExt.PACK.getPosition()] = 5;
+
+		DfsBlockCacheStats bitmapStats = new DfsBlockCacheStats();
+		incrementCounter(6, () -> bitmapStats
+				.incrementMiss(new TestKey(PackExt.BITMAP_INDEX)));
+		missCounts[PackExt.BITMAP_INDEX.getPosition()] = 6;
+
+		DfsBlockCacheStats indexStats = new DfsBlockCacheStats();
+		incrementCounter(7,
+				() -> indexStats.incrementMiss(new TestKey(PackExt.INDEX)));
+		missCounts[PackExt.INDEX.getPosition()] = 7;
+
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("name",
+						List.of(packStats, bitmapStats, indexStats));
+
+		assertArrayEquals(aggregatedBlockCacheStats.getMissCount(), missCounts);
+	}
+
+	@Test
+	public void getTotalRequestCount_aggregatesRequestCounts() {
+		long[] totalRequestCounts = createEmptyStatsArray();
+
+		DfsBlockCacheStats packStats = new DfsBlockCacheStats();
+		incrementCounter(5, () -> {
+			packStats.incrementHit(new TestKey(PackExt.PACK));
+			packStats.incrementMiss(new TestKey(PackExt.PACK));
+		});
+		totalRequestCounts[PackExt.PACK.getPosition()] = 10;
+
+		DfsBlockCacheStats bitmapStats = new DfsBlockCacheStats();
+		incrementCounter(6, () -> {
+			bitmapStats.incrementHit(new TestKey(PackExt.BITMAP_INDEX));
+			bitmapStats.incrementMiss(new TestKey(PackExt.BITMAP_INDEX));
+		});
+		totalRequestCounts[PackExt.BITMAP_INDEX.getPosition()] = 12;
+
+		DfsBlockCacheStats indexStats = new DfsBlockCacheStats();
+		incrementCounter(7, () -> {
+			indexStats.incrementHit(new TestKey(PackExt.INDEX));
+			indexStats.incrementMiss(new TestKey(PackExt.INDEX));
+		});
+		totalRequestCounts[PackExt.INDEX.getPosition()] = 14;
+
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("name",
+						List.of(packStats, bitmapStats, indexStats));
+
+		assertArrayEquals(aggregatedBlockCacheStats.getTotalRequestCount(),
+				totalRequestCounts);
+	}
+
+	@Test
+	public void getHitRatio_aggregatesHitRatios() {
+		long[] hitRatios = createEmptyStatsArray();
+
+		DfsBlockCacheStats packStats = new DfsBlockCacheStats();
+		incrementCounter(5,
+				() -> packStats.incrementHit(new TestKey(PackExt.PACK)));
+		hitRatios[PackExt.PACK.getPosition()] = 100;
+
+		DfsBlockCacheStats bitmapStats = new DfsBlockCacheStats();
+		incrementCounter(6, () -> {
+			bitmapStats.incrementHit(new TestKey(PackExt.BITMAP_INDEX));
+			bitmapStats.incrementMiss(new TestKey(PackExt.BITMAP_INDEX));
+		});
+		hitRatios[PackExt.BITMAP_INDEX.getPosition()] = 50;
+
+		DfsBlockCacheStats indexStats = new DfsBlockCacheStats();
+		incrementCounter(7,
+				() -> indexStats.incrementMiss(new TestKey(PackExt.INDEX)));
+		hitRatios[PackExt.INDEX.getPosition()] = 0;
+
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("Name",
+						List.of(packStats, bitmapStats, indexStats));
+
+		assertArrayEquals(aggregatedBlockCacheStats.getHitRatio(), hitRatios);
+	}
+
+	@Test
+	public void getEvictions_aggregatesEvictions() {
+		long[] evictions = createEmptyStatsArray();
+
+		DfsBlockCacheStats packStats = new DfsBlockCacheStats();
+		incrementCounter(5,
+				() -> packStats.incrementEvict(new TestKey(PackExt.PACK)));
+		evictions[PackExt.PACK.getPosition()] = 5;
+
+		DfsBlockCacheStats bitmapStats = new DfsBlockCacheStats();
+		incrementCounter(6, () -> bitmapStats
+				.incrementEvict(new TestKey(PackExt.BITMAP_INDEX)));
+		evictions[PackExt.BITMAP_INDEX.getPosition()] = 6;
+
+		DfsBlockCacheStats indexStats = new DfsBlockCacheStats();
+		incrementCounter(7,
+				() -> indexStats.incrementEvict(new TestKey(PackExt.INDEX)));
+		evictions[PackExt.INDEX.getPosition()] = 7;
+
+		BlockCacheStats aggregatedBlockCacheStats = AggregatedBlockCacheStats
+				.fromStatsList("Name",
+						List.of(packStats, bitmapStats, indexStats));
+
+		assertArrayEquals(aggregatedBlockCacheStats.getEvictions(), evictions);
+	}
+
+	private static void incrementCounter(int amount, Runnable fn) {
+		for (int i = 0; i < amount; i++) {
+			fn.run();
+		}
+	}
+
+	private static long[] createEmptyStatsArray() {
+		return new long[PackExt.values().length];
+	}
+
+	private static class TestKey extends DfsStreamKey {
+		TestKey(PackExt packExt) {
+			super(0, packExt);
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			return false;
+		}
+	}
+}
\ No newline at end of file
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackExtBlockCacheTableTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackExtBlockCacheTableTest.java
index f2a5abcacd..c5c964bcab 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackExtBlockCacheTableTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/internal/storage/dfs/PackExtBlockCacheTableTest.java
@@ -31,7 +31,6 @@ import java.util.Map;
 import org.eclipse.jgit.internal.storage.dfs.DfsBlockCache.Ref;
 import org.eclipse.jgit.internal.storage.dfs.DfsBlockCache.RefLoader;
 import org.eclipse.jgit.internal.storage.dfs.DfsBlockCacheConfig.DfsBlockCachePackExtConfig;
-import org.eclipse.jgit.internal.storage.dfs.DfsBlockCacheTable.DfsBlockCacheStats;
 import org.eclipse.jgit.internal.storage.pack.PackExt;
 import org.junit.Test;
 import org.mockito.Mockito;