Re: Ideas for memory management hackers (2)

Stephen Williams (steve@icarus.icarus.com)
Tue, 18 Nov 1997 11:21:50 +0000

How 'bout a means for device drivers (modules) to lock a stretch of
process pages into memory, get physical addresses, and be able to set up
i.e. DMA directly into those pages.

NT does support this sort of thing, sorta, with its DIRECT IO. (NT has
other problems that make it slow:-)

I understand that it is a bad idea in general, but I am usually faced with
devices transferring large images (i.e. 300DPI 11"x17" Gray images) and
I find myself getting a bunch of pages, marking them reserved, and using
mmap to share them with the process.

(I have a sample module that shows how to do this, if anybody is interested.)

-- 
Steve Williams
steve@icarus.com
steve@picturel.com


"The woods are lovely, dark and deep.  But I have promises to keep,
And lines to code before I sleep, And lines to code before I sleep."