HBASE-17738 BucketCache startup is slow - addendum (Ram)

hbase-common/src/main/java/org/apache/hadoop/hbase/util/ByteBufferArray.java

@@ -44,14 +44,15 @@ import com.google.common.annotations.VisibleForTesting;
  * reading/writing data from this large buffer with a position and offset
  */
 @InterfaceAudience.Private
-public final class ByteBufferArray {
+public class ByteBufferArray {
   private static final Log LOG = LogFactory.getLog(ByteBufferArray.class);
 
   public static final int DEFAULT_BUFFER_SIZE = 4 * 1024 * 1024;
   @VisibleForTesting
   ByteBuffer buffers[];
   private int bufferSize;
-  private int bufferCount;
+  @VisibleForTesting
+  int bufferCount;
 
   /**
    * We allocate a number of byte buffers as the capacity. In order not to out
@@ -75,12 +76,13 @@ public final class ByteBufferArray {
     createBuffers(directByteBuffer, allocator);
   }
 
-  private void createBuffers(boolean directByteBuffer, ByteBufferAllocator allocator)
+  @VisibleForTesting
+  void createBuffers(boolean directByteBuffer, ByteBufferAllocator allocator)
       throws IOException {
-    int threadCount = Runtime.getRuntime().availableProcessors();
+    int threadCount = getThreadCount();
     ExecutorService service = new ThreadPoolExecutor(threadCount, threadCount, 0L,
         TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>());
-    int perThreadCount = Math.round((float) (bufferCount) / threadCount);
+    int perThreadCount = (int)Math.floor((double) (bufferCount) / threadCount);
     int lastThreadCount = bufferCount - (perThreadCount * (threadCount - 1));
     Future<ByteBuffer[]>[] futures = new Future[threadCount];
     try {
@@ -109,6 +111,11 @@ public final class ByteBufferArray {
     this.buffers[bufferCount] = ByteBuffer.allocate(0);
   }
 
+  @VisibleForTesting
+  int getThreadCount() {
+    return Runtime.getRuntime().availableProcessors();
+  }
+
   /**
    * A callable that creates buffers of the specified length either onheap/offheap using the
    * {@link ByteBufferAllocator}

hbase-common/src/test/java/org/apache/hadoop/hbase/util/TestByteBufferArray.java

@@ -79,4 +79,43 @@ public class TestByteBufferArray {
       }
     }
   }
+
+  @Test
+  public void testByteBufferCreation1() throws Exception {
+    ByteBufferAllocator allocator = new ByteBufferAllocator() {
+      @Override
+      public ByteBuffer allocate(long size, boolean directByteBuffer) throws IOException {
+        if (directByteBuffer) {
+          return ByteBuffer.allocateDirect((int) size);
+        } else {
+          return ByteBuffer.allocate((int) size);
+        }
+      }
+    };
+    ByteBufferArray array = new DummyByteBufferArray(7 * 1024 * 1024, false, allocator);
+    // overwrite
+    array.bufferCount = 25;
+    array.buffers = new ByteBuffer[array.bufferCount + 1];
+    array.createBuffers(true, allocator);
+    for (int i = 0; i < array.buffers.length; i++) {
+      if (i == array.buffers.length - 1) {
+        assertEquals(array.buffers[i].capacity(), 0);
+      } else {
+        assertEquals(array.buffers[i].capacity(), 458752);
+      }
+    }
+  }
+
+  private static class DummyByteBufferArray extends ByteBufferArray {
+
+    public DummyByteBufferArray(long capacity, boolean directByteBuffer,
+        ByteBufferAllocator allocator) throws IOException {
+      super(capacity, directByteBuffer, allocator);
+    }
+
+    @Override
+    int getThreadCount() {
+      return 16;
+    }
+  }
 }