On Mon 14-10-19 18:23:00, Anshuman Khandual wrote: > > > On 10/14/2019 05:47 PM, Michal Hocko wrote: > > On Fri 11-10-19 13:29:32, Andrew Morton wrote: > >> alloc_gigantic_page() implements an allocation method where it scans over > >> various zones looking for a large contiguous memory block which could not > >> have been allocated through the buddy allocator. A subsequent patch which > >> tests arch page table helpers needs such a method to allocate PUD_SIZE > >> sized memory block. In the future such methods might have other use cases > >> as well. So alloc_gigantic_page() has been split carving out actual > >> memory allocation method and made available via new > >> alloc_gigantic_page_order(). > > > > You are exporting a helper used for hugetlb internally. Is this really > > Right, because the helper i.e alloc_gigantic_page() is generic enough which > scans over various zones to allocate a page order which could not be allocated > through the buddy. Only thing which is HugeTLB specific in there, is struct > hstate from where the order is derived with huge_page_order(). Otherwise it > is very generic. > > > what is needed? I haven't followed this patchset but don't you simply > > Originally I had just implemented similar allocator inside the test itself > but then figured that alloc_gigantic_page() can be factored out to create > a generic enough allocator helper. > > > need a generic 1GB allocator? If yes then you should be looking at > > The test needs a PUD_SIZE allocator. > > > alloc_contig_range. > > IIUC alloc_contig_range() requires (start pfn, end pfn) for the region to be > allocated. But before that all applicable zones need to be scanned to figure > out any available and suitable pfn range for alloc_contig_range() to try. In > this case pfn_range_valid_gigantic() check seemed reasonable while scanning > the zones. > > If pfn_range_valid_gigantic() is good enough or could be made more generic, > then the new factored alloc_gigantic_page_order() could be made a helper in > mm/page_alloc.c OK, thanks for the clarification. This all means that this patch is not the right approach. If you need a more generic alloc_contig_range then add it to page_alloc.c and make it completely independent on the hugetlb config and the code. Hugetlb allocator can reuse that helper. -- Michal Hocko SUSE Labs
