What Is Direct Memory Access?

Direct memory access (DMA, Direct Memory Access) is a function provided by some computer bus architectures, which enables data to be sent directly from additional devices (such as disk drives) to the computer's motherboard memory.

A memory section is usually specified for direct memory access. in

DMA is an important feature of all modern computers. It allows hardware devices of different speeds to communicate without relying on a large number of central processing units.

DMA causes

In addition to being related to hardware interaction, DMA can also reduce the cost of expensive memory consumption. Such as large copy behavior or scatter-gather operation, from the central processing unit to the dedicated DMA engine.

In the field of computer computing, remote direct memory access (English: remote direct memory access , RDMA ) is a direct memory access technology that transfers data directly from the memory of one computer to another without the intervention of both operating systems. . This allows high-throughput, low-latency network communications, and is particularly suitable for use in massively parallel computer clusters.

RDMA supports zero-copy network transmission. By enabling the network adapter to transfer data directly between application memory, it is no longer necessary to copy data between application memory and the operating system buffer. This transfer does not require the participation of a central processing unit, CPU cache, or context exchange, and the transfer can operate in parallel with other system operations. When an application performs an RDMA read or write request, the application data is transferred directly to the network, reducing latency and enabling fast message transfers.

However, this strategy also shows that the target node will not receive notification of completion of the request (one-way communication) and other related issues. ^[2]