Re: support for sata7 Streaming Feature Set?

From: Jeff Garzik
Date: Thu May 18 2006 - 11:36:18 EST

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.


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