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ByteBufferへのコピー速度比較

java

JavaでByteBufferへのコピーを行う際の速度を簡単に比較してみました。java.nio.ByteBuffer#put(byte)で1byteずつ書き込んでいくのでなければ大体同じですね。

Heap上のbyte arrayをコピー

java.nio.ByteBuffer#put(byte[], int, int)

        byte[] bs = new byte[256 * 1024 * 1024];
        ByteBuffer src = ByteBuffer.wrap(bs);
        ByteBuffer dst = ByteBuffer.allocate(bs.length);
        long start = System.currentTimeMillis();


        dst.put(src.array(), 0, src.remaining());
        System.out.println("heap.byte_array: ByteBuffer.put(byte[], int, int): " + (System.currentTimeMillis() - start));

=> heap.byte_array: ByteBuffer.put(byte[], int, int): 73

java.nio.ByteBuffer#put(java.nio.ByteBuffer)

        dst.put(src);
        System.out.println("heap.byte_array: ByteBuffer.put(java.nio.ByteBuffer): " + (System.currentTimeMillis() - start));

=> heap.byte_array: ByteBuffer.put(java.nio.ByteBuffer): 69

java.nio.ByteBuffer#put(byte) with loop

        for (int i = 0; i < src.remaining(); i++)
            dst.put(src.get());
        System.out.println("heap.byte_array: ByteBuffer.put(byte): " + (System.currentTimeMillis() - start));

=> heap.byte_array: ByteBuffer.put(byte): 380

Heap上のByteBufferをコピー

java.nio.ByteBuffer#put(byte[], int, int)

        ByteBuffer src = ByteBuffer.allocate(256 * 1024 * 1024);
        ByteBuffer dst = ByteBuffer.allocate(256 * 1024 * 1024);
        long start = System.currentTimeMillis();

        dst.put(src.array(), 0, src.remaining());
        System.out.println("heap.bb: ByteBuffer.put(byte[], int, int): " + (System.currentTimeMillis() - start));

=> heap.bb: ByteBuffer.put(byte[], int, int): 72

java.nio.ByteBuffer#put(java.nio.ByteBuffer)

        dst.put(src);
        System.out.println("heap.bb: ByteBuffer.put(java.nio.ByteBuffer): " + (System.currentTimeMillis() - start));

=> heap.bb: ByteBuffer.put(java.nio.ByteBuffer): 70

java.nio.ByteBuffer#put(byte) with loop

        for (int i = 0; i < src.remaining(); i++)
            dst.put(src.get());
        System.out.println("heap.bb: ByteBuffer.put(byte): " + (System.currentTimeMillis() - start));

Off heap上のByteBufferをコピー

java.nio.ByteBuffer#put(byte[], int, int)

        ByteBuffer src = ByteBuffer.allocateDirect(256 * 1024 * 1024);
        ByteBuffer dst = ByteBuffer.allocate(256 * 1024 * 1024);
        long start = System.currentTimeMillis();

        dst.put(src.array(), 0, src.remaining());
        System.out.println("off-heap.bb: ByteBuffer.put(byte[], int, int): " + (System.currentTimeMillis() - start));

=> java.lang.UnsupportedOperationException (it doesn't have array inside)

java.nio.ByteBuffer#put(java.nio.ByteBuffer)

        dst.put(src);
        System.out.println("off-heap.bb: ByteBuffer.put(java.nio.ByteBuffer): " + (System.currentTimeMillis() - start));

=> off-heap.bb: ByteBuffer.put(java.nio.ByteBuffer): 72

java.nio.ByteBuffer#put(byte) with loop

        for (int i = 0; i < src.remaining(); i++)
            dst.put(src.get());
        System.out.println("off-heap.bb: ByteBuffer.put(byte): " + (System.currentTimeMillis() - start));

=> off-heap.bb: ByteBuffer.put(byte): 358