ZeroCopyTransfers

ZeroCopyTransfers refers to a data transfer technique that aims to minimize or eliminate the need for the operating system to copy data between kernel space and user space. Traditional data transfer operations often involve multiple memory copies, which can be a bottleneck for high-performance applications, especially those dealing with large amounts of data like network servers or file transfer programs.

In a typical scenario, when an application requests data from a network socket or a file, the operating system's kernel first receives the data into its own buffer. Then, the application requests to read this data, which triggers another copy operation from the kernel buffer to the application's user-space buffer. The same process occurs in reverse when an application writes data to a network socket or file.

Zero-copy techniques, such as `sendfile()` system call in Unix-like systems or `IO_COMPLETION_ROUTINE` with specific flags in Windows, allow data to be transferred directly from one memory buffer to another, often bypassing the CPU and user-space involvement entirely. This is achieved by leveraging hardware features like Direct Memory Access (DMA) or by manipulating memory descriptors. By reducing or eliminating these redundant copies, zero-copy transfers significantly improve throughput and reduce CPU utilization, leading to better overall system performance and scalability. However, the implementation and availability of zero-copy mechanisms can vary across operating systems and hardware architectures.