pinmemory

Pin memory, commonly referred to as page-locked host memory, is a region of RAM that is pinned to physical memory so the operating system will not page it out to disk. In the context of GPU computing, pin memory describes host memory that is explicitly marked as non-pageable to enable faster and more reliable data transfers between the CPU and the device.

In many GPU programming environments, such as CUDA, pinned memory is allocated or registered so that the device driver can use direct memory access (DMA) to move data to and from the host without incurring paging delays. Pinned memory also supports asynchronous copy operations, allowing data transfers to overlap with computation when used with streams or other concurrency mechanisms. Some variants of pin memory can be mapped into the device’s address space for direct access by kernels, enabling zero-copy or unified memory scenarios.

The main advantages of pin memory are reduced transfer latency and higher bandwidth for host-device data movement, along with the possibility of overlapping computation and communication. However, pinning memory has trade-offs. It reduces the amount of RAM available for paging, which can affect overall system responsiveness if overused. Allocation of pinned memory is typically more expensive and can lead to memory fragmentation. There are practical limits on how much memory can be pinned, and its benefits are most noticeable for large or frequent transfers.

Common usage guidelines recommend pinning memory for sizable, repeated host-device transfers and freeing it promptly when it is no longer needed. Pin memory is released with appropriate deallocation or unregistration calls. See also GPU memory, Direct Memory Access, and pageable versus pinned memory concepts.