by Matthew Wilcox

[permalink] [raw]

Subject: Re: [RFC PATCH 10/11] shmem: add large folio support to the write path

On Sat, Oct 28, 2023 at 09:15:50PM +0000, Daniel Gomez wrote:
> +++ b/mm/shmem.c
> @@ -1621,6 +1621,9 @@ static struct folio *shmem_alloc_folio(gfp_t gfp, struct shmem_inode_info *info,
> pgoff_t ilx;
> struct page *page;
>
> + if ((order != 0) && !(gfp & VM_HUGEPAGE))
> + gfp |= __GFP_COMP;

This is silly. Just set it unconditionally.

> +static inline unsigned int
> +shmem_mapping_size_order(struct address_space *mapping, pgoff_t index,
> + size_t size, struct shmem_sb_info *sbinfo)
> +{
> + unsigned int order = ilog2(size);
> +
> + if ((order <= PAGE_SHIFT) ||
> + (!mapping_large_folio_support(mapping) || !sbinfo->noswap))
> + return 0;
> +
> + order -= PAGE_SHIFT;

You know we have get_order(), right?

2023-10-31 07:04:25

by Hannes Reinecke

[permalink] [raw]

Subject: Re: [RFC PATCH 09/11] shmem: add order arg to shmem_alloc_folio()

On 10/28/23 23:15, Daniel Gomez wrote:
> Add folio order argument to the shmem_alloc_folio() and merge it with
> the shmem_alloc_folio_huge(). Return will make use of the new
> page_rmappable_folio() where order-0 and high order folios are
> both supported.
>
> Signed-off-by: Daniel Gomez <[email protected]>
> ---
> mm/shmem.c | 33 ++++++++++-----------------------
> 1 file changed, 10 insertions(+), 23 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d8dc2ceaba18..fc7605da4316 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1614,40 +1614,27 @@ static gfp_t limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
> return result;
> }
>
> -static struct folio *shmem_alloc_hugefolio(gfp_t gfp,
> - struct shmem_inode_info *info, pgoff_t index)
> +static struct folio *shmem_alloc_folio(gfp_t gfp, struct shmem_inode_info *info,
> + pgoff_t index, unsigned int order)
> {
> struct mempolicy *mpol;
> pgoff_t ilx;
> struct page *page;
>
> - mpol = shmem_get_pgoff_policy(info, index, HPAGE_PMD_ORDER, &ilx);
> - page = alloc_pages_mpol(gfp, HPAGE_PMD_ORDER, mpol, ilx, numa_node_id());
> + mpol = shmem_get_pgoff_policy(info, index, order, &ilx);
> + page = alloc_pages_mpol(gfp, order, mpol, ilx, numa_node_id());
> mpol_cond_put(mpol);
>
> return page_rmappable_folio(page);
> }
>
> -static struct folio *shmem_alloc_folio(gfp_t gfp,
> - struct shmem_inode_info *info, pgoff_t index)
> -{
> - struct mempolicy *mpol;
> - pgoff_t ilx;
> - struct page *page;
> -
> - mpol = shmem_get_pgoff_policy(info, index, 0, &ilx);
> - page = alloc_pages_mpol(gfp, 0, mpol, ilx, numa_node_id());
> - mpol_cond_put(mpol);
> -
> - return (struct folio *)page;
> -}
> -
> static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
> struct inode *inode, pgoff_t index,
> struct mm_struct *fault_mm, size_t len)
> {
> struct address_space *mapping = inode->i_mapping;
> struct shmem_inode_info *info = SHMEM_I(inode);
> + unsigned int order = 0;
> struct folio *folio;
> long pages;
> int error;
> @@ -1668,12 +1655,12 @@ static struct folio *shmem_alloc_and_add_folio(gfp_t gfp,
> index + HPAGE_PMD_NR - 1, XA_PRESENT))
> return ERR_PTR(-E2BIG);
>
> - folio = shmem_alloc_hugefolio(gfp, info, index);
> + folio = shmem_alloc_folio(gfp, info, index, HPAGE_PMD_ORDER);
> if (!folio)
> count_vm_event(THP_FILE_FALLBACK);
> } else {
> - pages = 1;
> - folio = shmem_alloc_folio(gfp, info, index);
> + pages = 1UL << order;
> + folio = shmem_alloc_folio(gfp, info, index, order);
> }
> if (!folio)
> return ERR_PTR(-ENOMEM);
> @@ -1774,7 +1761,7 @@ static int shmem_replace_folio(struct folio **foliop, gfp_t gfp,
> */
> gfp &= ~GFP_CONSTRAINT_MASK;
> VM_BUG_ON_FOLIO(folio_test_large(old), old);
> - new = shmem_alloc_folio(gfp, info, index);
> + new = shmem_alloc_folio(gfp, info, index, 0);

Shouldn't you use folio_order(old) here?

Cheers,

Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
[email protected] +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
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