lkml.org 
[lkml]   [2008]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: Definition of x86 _PAGE_SPECIAL and sharing _PAGE_UNUSED1
Date
On Thursday 28 August 2008 05:02, Jeremy Fitzhardinge wrote:
> _PAGE_SPECIAL is overloading _PAGE_UNUSED1. Does it really leave
> _PAGE_UNUSED1 available for other uses, or does it become an exclusive
> user of that flag. Under what circumstances can they be shared?
>
> arch/x86/mm/pageattr-test.c is now using _PAGE_UNUSED1 as the flag used
> to make sure that huge pages are shattered properly (previously it used
> _PAGE_GLOBAL). Is that going to clash with _PAGE_SPECIAL?

Ah... pity it was hidden away there and not put into the include file.


> In other words, should we drop _PAGE_UNUSED1 altogether, or at least
> define how the its different users can coexist?

I don't feel strongly about it. But you should put your definition in
pgtable.h (and possibly explain how it coexists with _SPECIAL).


> Am I right in supposing that _PAGE_SPECIAL can only be set on user pages?

Yes.


> (Also, "SPECIAL" is awfully generic. Was there really no more
> descriptive name for this?)

I thought it was about on par with its counterpart, which is "normal".
Either way, I don't think a casual reader would get an adequate idea
of how it works in one word. normal ~= refcounted, special ~= !refcounted
I guess, but it is slightly more than that and besides, normal was there
first, and I think Linus coined it... if you can convince him to change
it then you have my blessing to change special into whatever you want.


\
 
 \ /
  Last update: 2008-08-28 02:35    [W:0.043 / U:0.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site