On Mon 14-01-19 09:30:55, Anshuman Khandual wrote: > > > On 01/13/2019 11:05 PM, Michal Hocko wrote: > > On Sat 12-01-19 15:56:38, 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. > > > > I agree that some unification is due but GFP_PGTABLE is not something to > > expose in generic gfp.h IMHO. It just risks an abuse. I would be looking > > Why would you think that it risks an abuse ? It does not create new semantics > of allocation in the buddy. Its just uses existing GFP_KERNEL allocation which > is then getting zeroed out. The risks (if any) is exactly same as GFP_KERNEL. Beucase my experience just tells me that people tend to use whatever they find and name fits what they think they need. > > at providing asm-generic implementation and reuse it to remove the code > > Does that mean GFP_PGTABLE can be created but not in gfp.h but in some other > memory related header file ? I would just keep it close to its users. If that is a single arch generic place then only better. But I suspect some arches have special requirements. > > duplication. But I haven't tried that to know that it will work out due > > to small/subtle differences between arches. > > IIUC from the allocation perspective GFP_ACCOUNT is the only thing which gets > added with GFP_PGTABLE for user page table for memcg accounting purpose. There > does not seem to be any other differences unless I am missing something. It's been some time since I've checked the last time. Some arches were using GPF_REPEAT (__GFP_RETRY_MAYFAIL) back then. I have removed most of those but some were doing a higher order allocations so they probably have stayed. -- Michal Hocko SUSE Labs _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
