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

[Jes Sorensen <jes@wildopensource.com>]

>>>>> "Christoph" == Christoph Hellwig <hch@infradead.org> writes:

>>  The code use the size to calculate, it could be changed either
>> way, don't think it's worth making the change.

Christoph> The current code is obsufcated, see the pages-1 stuff and
Christoph> co.  Please change it.

Both ways work, this is down to nitpicking for the sake of
nitpicking. Whatever, I'll change it.

Christoph> Please don't use the ->nopage approach thenm but do
Christoph> remap_pfn_range beforehand.  ->nopage is very nice if the
Christoph> region is actually backed by normal RAM, but what you're
Christoph> doing doesn't make much sense.
>>  Thats what I used to think, however you want the node-local setup
>> for performance reasons. Otherwise I would have switched to
>> remap_pfn_range.

Christoph> Then fixup remap_pfn_range (or rather add a new _node
Christoph> variant).  The current code relies on deep magic to work
Christoph> and could be broken by a new kernel release easily.

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.

Christoph> Jes, is it just me or are you trying to chicken out on all
Christoph> the real problems? :-)

It's you! I seems you're forgetting to do the real research before
trying to shoot something down ;-)

Cheers,
Jes