linux-kernel - Re: [PATCH mm-unstable v2 3/3] mm/hugetlb: use __GFP

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Message-ID: <24CDA80A-1CC1-4AD7-A35C-D1919DAA707D@nvidia.com>
Date: Fri, 16 Aug 2024 11:23:48 -0400
From: Zi Yan <ziy@...dia.com>
To: Yu Zhao <yuzhao@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Muchun Song <muchun.song@...ux.dev>,
 "Matthew Wilcox (Oracle)" <willy@...radead.org>, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, Frank van der Linden <fvdl@...gle.com>
Subject: Re: [PATCH mm-unstable v2 3/3] mm/hugetlb: use __GFP_COMP for
 gigantic folios

On 13 Aug 2024, at 23:54, Yu Zhao wrote:

> Use __GFP_COMP for gigantic folios to greatly reduce not only the
> amount of code but also the allocation and free time.
>
> LOC (approximately): +60, -240
>
> Allocate and free 500 1GB hugeTLB memory without HVO by:
>   time echo 500 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
>   time echo 0 >/sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages
>
>        Before  After
> Alloc  ~13s    ~10s
> Free   ~15s    <1s
>
> The above magnitude generally holds for multiple x86 and arm64 CPU
> models.
>
> Signed-off-by: Yu Zhao <yuzhao@...gle.com>
> Reported-by: Frank van der Linden <fvdl@...gle.com>
> ---
>  include/linux/hugetlb.h |   9 +-
>  mm/hugetlb.c            | 293 ++++++++--------------------------------
>  2 files changed, 62 insertions(+), 240 deletions(-)
>
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 3100a52ceb73..98c47c394b89 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -896,10 +896,11 @@ static inline bool hugepage_movable_supported(struct hstate *h)
>  /* Movability of hugepages depends on migration support. */
>  static inline gfp_t htlb_alloc_mask(struct hstate *h)
>  {
> -	if (hugepage_movable_supported(h))
> -		return GFP_HIGHUSER_MOVABLE;
> -	else
> -		return GFP_HIGHUSER;
> +	gfp_t gfp = __GFP_COMP | __GFP_NOWARN;
> +
> +	gfp |= hugepage_movable_supported(h) ? GFP_HIGHUSER_MOVABLE : GFP_HIGHUSER;
> +
> +	return gfp;
>  }
>
>  static inline gfp_t htlb_modify_alloc_mask(struct hstate *h, gfp_t gfp_mask)
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 71d469c8e711..efa77ce87dcc 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -56,16 +56,6 @@ struct hstate hstates[HUGE_MAX_HSTATE];
>  #ifdef CONFIG_CMA
>  static struct cma *hugetlb_cma[MAX_NUMNODES];
>  static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
> -static bool hugetlb_cma_folio(struct folio *folio, unsigned int order)
> -{
> -	return cma_pages_valid(hugetlb_cma[folio_nid(folio)], &folio->page,
> -				1 << order);
> -}
> -#else
> -static bool hugetlb_cma_folio(struct folio *folio, unsigned int order)
> -{
> -	return false;
> -}
>  #endif
>  static unsigned long hugetlb_cma_size __initdata;
>
> @@ -100,6 +90,17 @@ static void hugetlb_unshare_pmds(struct vm_area_struct *vma,
>  		unsigned long start, unsigned long end);
>  static struct resv_map *vma_resv_map(struct vm_area_struct *vma);
>
> +static void hugetlb_free_folio(struct folio *folio)
> +{
> +#ifdef CONFIG_CMA
> +	int nid = folio_nid(folio);
> +
> +	if (cma_free_folio(hugetlb_cma[nid], folio))
> +		return;
> +#endif
> +	folio_put(folio);
> +}
> +

It seems that we no longer use free_contig_range() to free gigantic
folios from alloc_contig_range(). Will it work? Or did I miss anything?


Best Regards,
Yan, Zi

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