Re: mapping user space buffer to kernel address space

From: Andrea Arcangeli (andrea@suse.de)
Date: Wed Oct 18 2000 - 08:02:56 EST


On Tue, Oct 17, 2000 at 09:26:07PM -0700, Linus Torvalds wrote:
> Maybe you mean PG_reserved?

Yes of course. (sorry for the typo)

> Quite frankly, the way I'd conceptually prefer people do these kinds of
> DMA buffers etc is to just have a "nopage()" function, and let that
> nopage() function just fill in the page from the DMA buffer directly. This
> would work fine, and would get rid of all the playing with PG_reserved
> etc.

And it would generate useless page faults as well. What's the point
of unmapping a page that can't be freed? Once the page gets freed
the mapping just gone away via munmap anyways. What's the point of
introducing that performance hit?

Andrea
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