Add "concurrencyLevel" option to DfsBlockCache

Allow for higher concurrency on DfsBlockCache by adding a configuration
for number of estimated concurrent requests.

Change-Id: Ia65e58ecb2c459b6d9c9697a2f715d933270f7e6
Signed-off-by: Philipp Marx <smigfu@googlemail.com>

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsBlockCache.java

@@ -182,7 +182,7 @@ public final class DfsBlockCache {
 			throw new IllegalArgumentException(JGitText.get().tSizeMustBeGreaterOrEqual1);
 
 		table = new AtomicReferenceArray<HashEntry>(tableSize);
-		loadLocks = new ReentrantLock[32];
+		loadLocks = new ReentrantLock[cfg.getConcurrencyLevel()];
 		for (int i = 0; i < loadLocks.length; i++)
 			loadLocks[i] = new ReentrantLock(true /* fair */);
 

org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/dfs/DfsBlockCacheConfig.java

@@ -47,6 +47,7 @@ import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_CORE_SECTION;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_DFS_SECTION;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_BLOCK_LIMIT;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_BLOCK_SIZE;
+import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_CONCURRENCY_LEVEL;
 import static org.eclipse.jgit.lib.ConfigConstants.CONFIG_KEY_STREAM_RATIO;
 
 import java.text.MessageFormat;
@@ -65,12 +66,14 @@ public class DfsBlockCacheConfig {
 	private long blockLimit;
 	private int blockSize;
 	private double streamRatio;
+	private int concurrencyLevel;
 
 	/** Create a default configuration. */
 	public DfsBlockCacheConfig() {
 		setBlockLimit(32 * MB);
 		setBlockSize(64 * KB);
 		setStreamRatio(0.30);
+		setConcurrencyLevel(32);
 	}
 
 	/**
@@ -110,6 +113,28 @@ public class DfsBlockCacheConfig {
 		return this;
 	}
 
+	/**
+	 * @return the estimated number of threads concurrently accessing the cache.
+	 *         <b>Default is 32.</b>
+	 * @since 4.6
+	 */
+	public int getConcurrencyLevel() {
+		return concurrencyLevel;
+	}
+
+	/**
+	 * @param newConcurrencyLevel
+	 *            the estimated number of threads concurrently accessing the
+	 *            cache.
+	 * @return {@code this}
+	 * @since 4.6
+	 */
+	public DfsBlockCacheConfig setConcurrencyLevel(
+			final int newConcurrencyLevel) {
+		concurrencyLevel = newConcurrencyLevel;
+		return this;
+	}
+
 	/**
 	 * @return highest percentage of {@link #getBlockLimit()} a single pack can
 	 *         occupy while being copied by the pack reuse strategy. <b>Default
@@ -154,6 +179,12 @@ public class DfsBlockCacheConfig {
 				CONFIG_KEY_BLOCK_SIZE,
 				getBlockSize()));
 
+		setConcurrencyLevel(rc.getInt(
+				CONFIG_CORE_SECTION,
+				CONFIG_DFS_SECTION,
+				CONFIG_KEY_CONCURRENCY_LEVEL,
+				getConcurrencyLevel()));
+
 		String v = rc.getString(
 				CONFIG_CORE_SECTION,
 				CONFIG_DFS_SECTION,

org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java

@@ -145,6 +145,13 @@ public class ConfigConstants {
 	/** The "blockSize" key */
 	public static final String CONFIG_KEY_BLOCK_SIZE = "blockSize";
 
+	/**
+	 * The "concurrencyLevel" key
+	 *
+	 * @since 4.6
+	 */
+	public static final String CONFIG_KEY_CONCURRENCY_LEVEL = "concurrencyLevel";
+
 	/** The "deltaBaseCacheLimit" key */
 	public static final String CONFIG_KEY_DELTA_BASE_CACHE_LIMIT = "deltaBaseCacheLimit";