Determining a direct memory access data transfer mode

摘要

In response to receiving a request for a DMA data transfer, a DMA transfer mode may be determined based on based on the size of the requested DMA data transfer and profile data of an I/O adapter. The profile data for the I/O adapter may include a physical location of the I/O adapter or a number of clients supported by the I/O adapter. The DMA transfer mode may also be determined based on a preference of an application or an I/O device. Moreover, the DMA transfer mode may be determined based on a CPU usage metric being outside of a threshold for the CPU usage metric or on a memory usage metric being outside of a threshold for the memory usage metric.

主权项

1. A system for determining a direct memory access (DMA) transfer mode, comprising:
a DMA unit to receive a request for a DMA data transfer and to perform the requested DMA data transfer using a determined DMA transfer mode; and an I/O adapter to determine the DMA transfer mode for the requested DMA data transfer based on the size of the requested DMA data transfer and profile data of the I/O adapter, the DMA transfer mode being one of a first mode or a second mode,
wherein, in the first mode, a first region of system memory is pre-allocated for use in DMA transfers, andwherein, in the second mode, a second region of system memory for use in a particular DMA transfer is allocated for the particular DMA transfer and deallocated when the particular DMA transfer is complete.