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SubjectRe: [PATCH V2] mm: Introduce GFP_PGTABLE
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Matthew Wilcox <willy@infradead.org> writes:

> On Wed, Jan 16, 2019 at 07:57:03AM +0100, Michal Hocko wrote:
>> On Wed 16-01-19 11:51:32, Anshuman Khandual wrote:
>> > All architectures have been defining their own PGALLOC_GFP as (GFP_KERNEL |
>> > __GFP_ZERO) and using it for allocating page table pages. This causes some
>> > code duplication which can be easily avoided. GFP_KERNEL allocated and
>> > cleared out pages (__GFP_ZERO) are required for page tables on any given
>> > architecture. This creates a new generic GFP flag flag which can be used
>> > for any page table page allocation. Does not cause any functional change.
>> >
>> > GFP_PGTABLE is being added into include/asm-generic/pgtable.h which is the
>> > generic page tabe header just to prevent it's potential misuse as a general
>> > allocation flag if included in include/linux/gfp.h.
>>
>> I haven't reviewed the patch yet but I am wondering whether this is
>> really worth it without going all the way down to unify the common code
>> and remove much more code duplication. Or is this not possible for some
>> reason?
>
> Exactly what I suggested doing in response to v1.
>
> Also, the approach taken here is crazy. x86 has a feature that no other
> architecture has bothered to implement yet -- accounting page tables
> to the process.

powerpc does __GFP_ACCOUNT for user page tables too. Shamelessly cribbed
from the x86 version of course :)

cheers

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