Re: [PATCH] mm: alloc_anon_folio: avoid doing vma_thp_gfp_mask in fallback cases

[Ryan Roberts]

On 29/03/2024 07:37, Barry Song wrote:
> From: Barry Song <v-songbaohua@xxxxxxxx>
> 
> Fallback rates surpassing 90% have been observed on phones utilizing 64KiB
> CONT-PTE mTHP. In these scenarios, when one out of every 16 PTEs fails
> to allocate large folios, the remaining 15 PTEs fallback. Consequently,
> invoking vma_thp_gfp_mask seems redundant in such cases. Furthermore,
> abstaining from its use can also contribute to improved code readability.
> 
> Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
> Cc: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
> Cc: John Hubbard <jhubbard@xxxxxxxxxx>
> Cc: David Hildenbrand <david@xxxxxxxxxx>
> Cc: Alistair Popple <apopple@xxxxxxxxxx>
> Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Cc: Itaru Kitayama <itaru.kitayama@xxxxxxxxx>
> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Yang Shi <shy828301@xxxxxxxxx>
> Cc: Yin Fengwei <fengwei.yin@xxxxxxxxx>
> Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
> Cc: Zi Yan <ziy@xxxxxxxxxx>
> Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>

Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>

> ---
>  mm/memory.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index c9c1031c2ecb..010e7bb20d2b 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4353,6 +4353,9 @@ static struct folio *alloc_anon_folio(struct vm_fault *vmf)
>  
>  	pte_unmap(pte);
>  
> +	if (!orders)
> +		goto fallback;
> +
>  	/* Try allocating the highest of the remaining orders. */
>  	gfp = vma_thp_gfp_mask(vma);
>  	while (orders) {