Messages in this thread | | | Date | Wed, 27 Aug 2008 17:47:34 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: Definition of x86 _PAGE_SPECIAL and sharing _PAGE_UNUSED1 |
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Nick Piggin wrote: > Ah... pity it was hidden away there and not put into the include file. >
Yes. I just prepped a patch to bring it out into the light.
> I don't feel strongly about it. But you should put your definition in > pgtable.h (and possibly explain how it coexists with _SPECIAL). >
Yes, that was my plan, but without knowing how _SPECIAL is used, it's a bit tricky. Is there a comment somewhere which describes who sets it and when? From a quick look, it seems it's set on newly added user pages which aren't COWed. Can they be shared file-backed pages? Anonymous pages? Device pages?
>> Am I right in supposing that _PAGE_SPECIAL can only be set on user pages? >> > > Yes. >
OK, that won't clash with CPA tests at all, since they're kernel only.
>> (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. >
It's only used in a couple of places, so giving it a longer name wouldn't cost much. _PAGE_USER_UNCOUNTED? But ugh, a lot of cross-arch churnpatch to do it.
J
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