A double buffer is a technique where two buffers are used to read and write data. One buffer is used for input/output operations while the other buffer is being filled or emptied. This approach is expected to improve performance compared to a single buffer because it reduces the delay caused by the CPU waiting for I/O operations to complete. With a single buffer, the CPU is idle while the buffer is being filled or emptied, which can lead to performance degradation.
Disk read or write operations involve several delay elements, including:
Seek Time: This is the time required for the read/write head to move to the correct location on the disk to read or write data.
Rotational Latency: This is the time required for the disk platter to rotate to the position where the read/write head can access the data.
Data Transfer Time: This is the time required to actually read or write the data once the read/write head is positioned correctly.
Using a double buffer can help reduce the impact of these delays on overall system performance. By using one buffer for I/O operations while the other is being filled or emptied, the CPU can continue to process other tasks while the I/O operations are taking place, reducing the impact of the seek time and rotational latency delays. Additionally, the double buffer technique can help to smooth out fluctuations in I/O processing times, which can improve overall system performance and reduce the likelihood of I/O-related bottlenecks.