efi_memmap_walk_uc, was Re: [patch] mspec driver for 2.6.12-rc2-mm3

From: Christoph Hellwig
Date: Mon Apr 25 2005 - 09:44:18 EST

On Mon, Apr 25, 2005 at 06:13:01AM -0400, Jes Sorensen wrote:
> Your approach doesn't work. This relies on first-touch to get
> performance, remap_pfn_range_node wouldn't work.
> Christoph> I'm pretty sure this was NACKed on the ia64 list, and SGI
> Christoph> was told to do a more generic efi memmap walk.
> >> No the issue back then was that the driver just took the memory
> >> and kept it to itself. The new approach exports it for other users.
> Christoph> That comment doesn't make sense at all to me. exports what
> Christoph> to what other users. And through what way. Please bring
> Christoph> this issue up on the ia64 list again. (also please post
> Christoph> this patch to linux-ia64, too)
> mspec_alloc_page can be called from anywhere by anyone who wants to
> allocate an uncached page. The old fetchop driver just took the
> uncached memory and kept to itself. Thats what I am talking about!
> Earlier versions of the patch has already been by the ia64 list, we're
> down to details here.

See the thread starting at

My reading is that it requests two things:

- not duplicating the EFI memmap walk in a new function but rather
have generic EFI memmap walk replaces the current efi_memmap_walk
- an uncached memory allocator below the driver (not in the driver!).
Your allocator design also doesn't seem to take many of the suggestions
and recommendations in that thread in account.
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