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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 13.07.24 06:01, Baolin Wang wrote: > > > On 2024/7/13 09:03, David Hildenbrand wrote: >> On 12.07.24 07:39, Gavin Shan wrote: >>> On 7/12/24 7:03 AM, 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. >>>> >>>> PAGECACHE (1 .. MAX_PAGECACHE_ORDER) >>>> >>>> ? But it's still unclear to me. >>>> >>>> At least DAX must stay special I think, and PAGECACHE should be >>>> capped at MAX_PAGECACHE_ORDER. >>>> >>> >>> David, I can help to clean it up. Could you please help to confirm the >>> following >> >> Thanks! >> >>> changes are exactly what you're suggesting? Hopefully, there are >>> nothing I've missed. >>> The original issue can be fixed by the changes. With the changes >>> applied, madvise(MADV_COLLAPSE) >>> returns with errno -22 in the test program. >>> >>> The fix tag needs to adjusted either. >>> >>> Fixes: 3485b88390b0 ("mm: thp: introduce multi-size THP sysfs interface") >>> >>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >>> index 2aa986a5cd1b..45909efb0ef0 100644 >>> --- a/include/linux/huge_mm.h >>> +++ b/include/linux/huge_mm.h >>> @@ -74,7 +74,12 @@ extern struct kobj_attribute shmem_enabled_attr; >>>    /* >>>     * Mask of all large folio orders supported for file THP. >>>     */ >>> -#define THP_ORDERS_ALL_FILE    (BIT(PMD_ORDER) | BIT(PUD_ORDER)) >> >> DAX doesn't have any MAX_PAGECACHE_ORDER restrictions (like hugetlb). So >> this should be >> >> /* >>  * FSDAX never splits folios, so the MAX_PAGECACHE_ORDER limit does not >>  * apply here. >>  */ >> THP_ORDERS_ALL_FILE_DAX ((BIT(PMD_ORDER) | BIT(PUD_ORDER)) >> >> Something like that >> >>> +#define THP_ORDERS_ALL_FILE_DAX                \ >>> +       ((BIT(PMD_ORDER) | BIT(PUD_ORDER)) & (BIT(MAX_PAGECACHE_ORDER >>> + 1) - 1)) >>> +#define THP_ORDERS_ALL_FILE_DEFAULT    \ >>> +       ((BIT(MAX_PAGECACHE_ORDER + 1) - 1) & ~BIT(0)) >>> +#define THP_ORDERS_ALL_FILE            \ >>> +       (THP_ORDERS_ALL_FILE_DAX | THP_ORDERS_ALL_FILE_DEFAULT) >> >> Maybe we can get rid of THP_ORDERS_ALL_FILE (to prevent abuse) and fixup >> THP_ORDERS_ALL instead. >> >>>    /* >>>     * Mask of all large folio orders supported for THP. >>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >>> index 2120f7478e55..4690f33afaa6 100644 >>> --- a/mm/huge_memory.c >>> +++ b/mm/huge_memory.c >>> @@ -88,9 +88,17 @@ unsigned long __thp_vma_allowable_orders(struct >>> vm_area_struct *vma, >>>           bool smaps = tva_flags & TVA_SMAPS; >>>           bool in_pf = tva_flags & TVA_IN_PF; >>>           bool enforce_sysfs = tva_flags & TVA_ENFORCE_SYSFS; >>> +       unsigned long supported_orders; >>> + >>>           /* Check the intersection of requested and supported orders. */ >>> -       orders &= vma_is_anonymous(vma) ? >>> -                       THP_ORDERS_ALL_ANON : THP_ORDERS_ALL_FILE; >>> +       if (vma_is_anonymous(vma)) >>> +               supported_orders = THP_ORDERS_ALL_ANON; >>> +       else if (vma_is_dax(vma)) >>> +               supported_orders = THP_ORDERS_ALL_FILE_DAX; >>> +       else >>> +               supported_orders = THP_ORDERS_ALL_FILE_DEFAULT; >> >> This is what I had in mind. >> >> But, do we have to special-case shmem as well or will that be handled >> correctly? > > For anonymous shmem, it is now same as anonymous THP, which can utilize > THP_ORDERS_ALL_ANON. > For tmpfs, we currently only support PMD-sized THP > (will support more larger orders in the future). Therefore, I think we > can reuse THP_ORDERS_ALL_ANON for shmem now: > > if (vma_is_anonymous(vma) || shmem_file(vma->vm_file))) > supported_orders = THP_ORDERS_ALL_ANON; > ...... > It should be THP_ORDERS_ALL_FILE_DEFAULT (MAX_PAGECACHE_ORDER imitation applies). -- Cheers, David / dhildenb