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ByteBuf very poor sequential read/write performance compared with ByteBuffer or byte[]

See original GitHub issue

Expected behavior

ByteBuf better performance

Actual behavior

ByteBuf seq R/w is the worst

Steps to reproduce

$java SeqRwPerf
Netty ByteBuf seq R/W time: 5668ms
Java ByteBuffer seq R/W time: 4241ms
Java byte[] seq R/W time: 1528ms

Minimal yet complete reproducer code (or URL to code)

import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufAllocator;

import java.nio.ByteBuffer;

public class SeqRwPerf {

    static final ByteBufAllocator ALLOC = ByteBufAllocator.DEFAULT;
    static final int N = 4 << 10, M = 100 * N;

    public static void main(String[] args) {
        long ta = System.currentTimeMillis();
        testNettyRw();
        long tb = System.currentTimeMillis();
        System.out.printf("Netty ByteBuf seq R/W time: %sms%n", tb - ta);

        ta = System.currentTimeMillis();
        testNioRw();
        tb = System.currentTimeMillis();
        System.out.printf("Java ByteBuffer seq R/W time: %sms%n", tb - ta);

        ta = System.currentTimeMillis();
        testByteaRw();
        tb = System.currentTimeMillis();
        System.out.printf("Java byte[] seq R/W time: %sms%n", tb - ta);
    }

    public static void testNettyRw() {
        for (int i = 0; i < M; ++i) {
            ByteBuf buf = ALLOC.buffer(N);

            for (int j = 0; j < N; ++j) {
                buf.writeByte(j);
            }
            for (int j = 0; j < N; ++j) {
                byte b = buf.readByte();
                assertEquals(b, (byte) j);
            }

            buf.release();
        }
    }

    public static void testNioRw() {
        for (int i = 0; i < M; ++i) {
            ByteBuffer buf = ByteBuffer.allocate(N);

            for (int j = 0; j < N; ++j) {
                buf.put((byte)j);
            }
            buf.flip();
            for (int j = 0; j < N; ++j) {
                byte b = buf.get();
                assertEquals(b, (byte) j);
            }
        }
    }

    public static void testByteaRw() {
        for (int i = 0; i < M; ++i) {
            byte[] buf = new byte[N];

            for (int j = 0; j < N; ++j) {
                buf[j] = (byte)j;
            }
            for (int j = 0; j < N; ++j) {
                byte b = buf[j];
                assertEquals(b, (byte) j);
            }
        }
    }

    static void assertEquals(int a, int b) {
        if (a != b) throw new AssertionError(a + " != " + b);
    }

}