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SubjectRe: [RFC PATCH 0/5] Use an alternative to _PAGE_PROTNONE for _PAGE_NUMA v2
On Tue, Apr 08, 2014 at 05:46:52PM +0100, Mel Gorman wrote:
> On Tue, Apr 08, 2014 at 08:22:15AM -0700, Linus Torvalds wrote:
> > On Tue, Apr 8, 2014 at 7:40 AM, H. Peter Anvin <hpa@zytor.com> wrote:
> > >
> > > David, is your patchset going to be pushed in this merge window as expected?
> >
> > Apparently aiming for 3.16 right now.
> >
>
> > > That being said, these bits are precious, and if this ends up being a
> > > case where "only Xen needs another bit" once again then Xen should
> > > expect to get kicked to the curb at a moment's notice.
> >
> > Quite frankly, I don't think it's a Xen-only issue. The code was hard
> > to figure out even without the Xen issues. For example, nobody ever
> > explained to me why it
> >
> > (a) could be the same as PROTNONE on x86
> > (b) could not be the same as PROTNONE in general
>
> This series exists in response to your comment
>
> I fundamentally think that it was a horrible horrible disaster to
> make _PAGE_NUMA alias onto _PAGE_PROTNONE.
>
> As long as _PAGE_NUMA aliases to _PAGE_PROTNONE on x86 then the core has to
> play games to take that into account and the code will be "hard to figure
> out even without the Xen issues".

Is what you want for _PAGE_NUMA to disappear from arch/x86 and instead
use _PAGE_PROTNONE with comments explaining why and leave the core as it
is?

--
Mel Gorman
SUSE Labs


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