[JAVA] Add java binding for Options.block_cache.

Summary:
Add java bindings for Options.block_cache and allow DbBenchmark to
set cache_size.

Test Plan:
make rocksdbjava
make jtest
make jdb_Bench

Reviewers: haobo, sdong, ankgup87

Reviewed By: ankgup87

CC: leveldb, dhruba

Differential Revision: https://reviews.facebook.net/D17481

java/org/rocksdb/Options.java

@@ -13,6 +13,7 @@ package org.rocksdb;
  * become out-of-scope to release the allocated memory in c++.
  */
 public class Options {
+  static final long DEFAULT_CACHE_SIZE = 8 << 20;
   /**
    * Construct options for opening a RocksDB.
    *
@@ -21,6 +22,7 @@ public class Options {
    */
   public Options() {
     nativeHandle_ = 0;
+    cacheSize_ = DEFAULT_CACHE_SIZE;
     newOptions();
   }
 
@@ -198,6 +200,24 @@ public class Options {
     return maxBackgroundCompactions(nativeHandle_);
   }
 
+  /**
+   * Set the amount of cache in bytes that will be used by RocksDB.
+   * If cacheSize is non-positive, then cache will not be used.
+   *
+   * DEFAULT: 8M
+   */
+  public Options setCacheSize(long cacheSize) {
+    cacheSize_ = cacheSize;
+    return this;
+  }
+
+  /**
+   * @return the amount of cache in bytes that will be used by RocksDB.
+   */
+  public long cacheSize() {
+    return cacheSize_;
+  }
+
   /**
    * Release the memory allocated for the current instance
    * in the c++ side.
@@ -231,4 +251,5 @@ public class Options {
   private native int maxBackgroundCompactions(long handle);
 
   long nativeHandle_;
+  long cacheSize_;
 }

java/org/rocksdb/RocksDB.java

@@ -33,7 +33,12 @@ public class RocksDB {
    */
   public static RocksDB open(String path) throws RocksDBException {
     RocksDB db = new RocksDB();
-    db.open0(path);
+
+    // This allows to use the rocksjni default Options instead of
+    // the c++ one.
+    Options options = new Options();
+    db.open(options.nativeHandle_, options.cacheSize_, path);
+    options.dispose();
     return db;
   }
 
@@ -44,7 +49,7 @@ public class RocksDB {
   public static RocksDB open(Options options, String path)
       throws RocksDBException {
     RocksDB db = new RocksDB();
-    db.open(options.nativeHandle_, path);
+    db.open(options.nativeHandle_, options.cacheSize_, path);
     return db;
   }
 
@@ -145,9 +150,8 @@ public class RocksDB {
   }
 
   // native methods
-  private native void open0(String path) throws RocksDBException;
   private native void open(
-      long optionsHandle, String path) throws RocksDBException;
+      long optionsHandle, long cacheSize, String path) throws RocksDBException;
   private native void put(
       long handle, byte[] key, int keyLen,
       byte[] value, int valueLen) throws RocksDBException;

java/org/rocksdb/benchmark/DbBenchmark.java

@@ -366,15 +366,25 @@ public class DbBenchmark {
     randSeed_ = (long) flags.get(Flag.seed);
     databaseDir_ = (String) flags.get(Flag.db);
     writesPerSeconds_ = (int) flags.get(Flag.writes_per_second);
+    cacheSize_ = (long) flags.get(Flag.cache_size);
     gen_ = new RandomGenerator(compressionRatio_);
     finishLock_ = new Object();
   }
 
+  private void prepareOptions(Options options) {
+    options.setCacheSize(cacheSize_);
+    if (!useExisting_) {
+      options.setCreateIfMissing(true);
+    }
+  }
+
   private void run() throws RocksDBException {
     if (!useExisting_) {
       destroyDb();
     }
-    open();
+    Options options = new Options();
+    prepareOptions(options);
+    open(options);
 
     printHeader();
 
@@ -426,7 +436,7 @@ public class DbBenchmark {
         }
       } else if (benchmark.equals("delete")) {
         destroyDb();
-        open();
+        open(options);
       } else {
         known = false;
         System.err.println("Unknown benchmark: " + benchmark);
@@ -467,6 +477,7 @@ public class DbBenchmark {
       }
       writeOpt.dispose();
     }
+    options.dispose();
     db_.close();
   }
 
@@ -495,8 +506,8 @@ public class DbBenchmark {
     }
   }
 
-  private void open() throws RocksDBException {
-    db_ = RocksDB.open(databaseDir_);
+  private void open(Options options) throws RocksDBException {
+    db_ = RocksDB.open(options, databaseDir_);
   }
 
   private void start() {
@@ -703,11 +714,11 @@ public class DbBenchmark {
       }
     },
 
-    cache_size(-1,
+    cache_size(-1L,
         "Number of bytes to use as a cache of uncompressed data.\n" +
         "\tNegative means use default settings.") {
       @Override public Object parseValue(String value) {
-        return Integer.parseInt(value);
+        return Long.parseLong(value);
       }
     },
 
@@ -794,6 +805,7 @@ public class DbBenchmark {
   final int threadNum_;
   final int writesPerSeconds_;
   final long randSeed_;
+  final long cacheSize_;
   final boolean useExisting_;
   final String databaseDir_;
   final double compressionRatio_;