Re: TCP RDMA option to accelerate NFS, CIFS, SCSI, etc.

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

> As I recall, Van's solution required an unconventional I/O system where DMA went
> straight into user memory right off the LAN chip. Not too many people make
> computers like that.

Actually it doesn't, although every PC today is your 'unconventional' system.
Many 10Mbit and almost all the 100Mbit cards do scatter gather DMA.  To do
zero copy means landing the buffer into memory that can become accessible to
the user, the rest of the benefits for single copy/checksum/user come with
DMA landing in purely kernel controlled space