Re: kmap_kiobuf()

David Woodhouse (dwmw2@infradead.org)
Wed, 28 Jun 2000 17:06:30 +0100

lord@sgi.com said:
> I always knew it would go down like a ton of bricks, because of the
> TLB flushing costs. As soon as you have a multi-cpu box this operation
> gets expensive, the code could be changed to do lazy tlb flushes on
> unmapping the pages, but you still have the cost every time you set a
> mapping up.

Aha - is this why kmap uses a pre-allocated set of PTEs? I got about that
far before deciding I had no clue what was going on and giving up.

MM is not exactly my field - I just know I want to be able to lock down a
user's buffer and treat it as if it were in kernel-space, passing its
address to functions which expect kernel buffers.

--
dwmw2






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