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SubjectRe: [PATCH] mm/page_alloc: Make alloc_gigantic_page() available for general use
On 16.10.19 12:28, Anshuman Khandual wrote:
> On 10/16/2019 02:28 PM, Michal Hocko wrote:
>> On Wed 16-10-19 13:04:53, Anshuman Khandual wrote:
>>> HugeTLB helper alloc_gigantic_page() implements fairly generic allocation
>>> method where it scans over various zones looking for a large contiguous pfn
>>> range before trying to allocate it with alloc_contig_range(). Other than
>>> deriving the requested order from 'struct hstate', there is nothing HugeTLB
>>> specific in there. This can be made available for general use to allocate
>>> contiguous memory which could not have been allocated through the buddy
>>> allocator.
>>> alloc_gigantic_page() has been split carving out actual allocation method
>>> which is then made available via new alloc_contig_pages() helper wrapped
>>> under CONFIG_CONTIG_ALLOC. All references to 'gigantic' have been replaced
>>> with more generic term 'contig'. Allocated pages here should be freed with
>>> free_contig_range() or by calling __free_page() on each allocated page.
>> Do we want to export this to modules? Apart from mostly styling issues
>> pointed by David this looks fine.
>> I do agree that a general allocator api belongs to page_alloc.c rather
>> than force people to invent their own and broken instances.
>>> Cc: Mike Kravetz <>
>>> Cc: Andrew Morton <>
>>> Cc: Vlastimil Babka <>
>>> Cc: Michal Hocko <>
>>> Cc: David Rientjes <>
>>> Cc: Andrea Arcangeli <>
>>> Cc: Oscar Salvador <>
>>> Cc: Mel Gorman <>
>>> Cc: Mike Rapoport <>
>>> Cc: Dan Williams <>
>>> Cc: Pavel Tatashin <>
>>> Cc: Matthew Wilcox <>
>>> Cc: David Hildenbrand <>
>>> Cc:
>>> Signed-off-by: Anshuman Khandual <>
>> After other issues mentioned by David get resolved you can add
> Just to confirm. Only the styling issues, right ? pfn_range_valid_contig(),
> pfn alignment and zone scanning all remain the same like before ?

Fine with me. Please do think about the alignment thingy. (I suggest to
just enforce an alignment to a power of two for now (and return NULL if
not a power of two), we can always relax that when needed - and then
think about a better search for !power of two)



David / dhildenb

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