Linear and link-list descriptor types can be chained to reduce software and hardware overhead. For example, if software allocates two noncontiguous 4 KB pages to store descriptors, then it can contiguously store BDs in the first page and make the last BD of the first page point to the first BD of the next available page. Because the next address pointer in linear descriptor is not required, this scheme reduces both memory usage and software overhead. The descriptor mode diagram (Figure 1) details this use case.
- Each descriptor is aligned to its natural size.
- Linear descriptor is 128-bit aligned.
- Link-list descriptor is 256-bit aligned.