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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 11.07.24 23:03, David Hildenbrand wrote: > On 11.07.24 22:46, Matthew Wilcox wrote: >> On Thu, Jul 11, 2024 at 08:48:40PM +1000, Gavin Shan wrote: >>> +++ b/mm/huge_memory.c >>> @@ -136,7 +136,8 @@ unsigned long __thp_vma_allowable_orders(struct vm_area_struct *vma, >>> >>> while (orders) { >>> addr = vma->vm_end - (PAGE_SIZE << order); >>> - if (thp_vma_suitable_order(vma, addr, order)) >>> + if (!(vma->vm_file && order > MAX_PAGECACHE_ORDER) && >>> + thp_vma_suitable_order(vma, addr, order)) >>> break; >> >> Why does 'orders' even contain potential orders that are larger than >> MAX_PAGECACHE_ORDER? >> >> We do this at the top: >> >> orders &= vma_is_anonymous(vma) ? >> THP_ORDERS_ALL_ANON : THP_ORDERS_ALL_FILE; >> >> include/linux/huge_mm.h:#define THP_ORDERS_ALL_FILE (BIT(PMD_ORDER) | BIT(PUD_ORDER)) >> >> ... and that seems very wrong. We support all kinds of orders for >> files, not just PMD order. We don't support PUD order at all. >> >> What the hell is going on here? > > yes, that's just absolutely confusing. I mentioned it to Ryan lately > that we should clean that up (I wanted to look into that, but am happy > if someone else can help). > > There should likely be different defines for > > DAX (PMD|PUD) > > SHMEM (PMD) -- but soon more. Not sure if we want separate ANON_SHMEM > for the time being. Hm. But shmem is already handles separately, so > maybe we can just ignore shmem here. Correction: of course <= MAX_PAGECACHE_ORDER But yeah, this needs cleanups -- Cheers, David / dhildenb