Re: support for sata7 Streaming Feature Set?

[Jeff Garzik <jeff@garzik.org>]

Tejun Heo wrote:
> One thing to think about before supporting streaming from/to harddisks 
> from userland is how to make data flow efficiently from userland to 
> kernel and back.  But, no matter what, kernel <-> userland usually 
> involves one data copy, so I don't think making sg similarly efficient 
> would be too difficult (it might be already).

Actually, the kernel usually maps userland pages, eliminating the need 
for a copy.  write(2) may have copied data into that page originally, 
but mmap(2) need not have.

	Jeff