[PATCH V2] mm: Introduce GFP_PGTABLE

Matthew Wilcox willy at infradead.org
Wed Jan 16 23:30:18 AEDT 2019


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.  Yet instead of spreading that goodness to all other
architectures, Anshuman has gone to more effort to avoid doing that.


More information about the Linuxppc-dev mailing list