2022-12-08 18:24:32

by Kairui Song

Subject: [PATCH 2/5] swap: avoid a redundant pte map if ra window is 1

From: Kairui Song <[email protected]>

Avoid a redundant pte map/unmap when swap readahead window is 1.

Signed-off-by: Kairui Song <[email protected]>
---
mm/swap_state.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 438d0676c5be..60136bda78e3 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -730,8 +730,6 @@ static void swap_ra_info(struct vm_fault *vmf,
}

faddr = vmf->address;
- orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
-
fpfn = PFN_DOWN(faddr);
ra_val = GET_SWAP_RA_VAL(vma);
pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
@@ -742,12 +740,11 @@ static void swap_ra_info(struct vm_fault *vmf,
atomic_long_set(&vma->swap_readahead_info,
SWAP_RA_VAL(faddr, win, 0));

- if (win == 1) {
- pte_unmap(orig_pte);
+ if (win == 1)
return;
- }

/* Copy the PTEs because the page table may be unmapped */
+ orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
if (fpfn == pfn + 1)
swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
else if (pfn == fpfn + 1)
--
2.35.2

2022-12-09 04:33:42

by Huang, Ying

Subject: Re: [PATCH 2/5] swap: avoid a redundant pte map if ra window is 1

Kairui Song <[email protected]> writes:

> From: Kairui Song <[email protected]>
>
> Avoid a redundant pte map/unmap when swap readahead window is 1.
>
> Signed-off-by: Kairui Song <[email protected]>
> ---
> mm/swap_state.c | 7 ++-----
> 1 file changed, 2 insertions(+), 5 deletions(-)

Good to reduce the line of code. Thanks!

Reviewed-by: "Huang, Ying" <[email protected]>

> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 438d0676c5be..60136bda78e3 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -730,8 +730,6 @@ static void swap_ra_info(struct vm_fault *vmf,
> }
>
> faddr = vmf->address;
> - orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
> -
> fpfn = PFN_DOWN(faddr);
> ra_val = GET_SWAP_RA_VAL(vma);
> pfn = PFN_DOWN(SWAP_RA_ADDR(ra_val));
> @@ -742,12 +740,11 @@ static void swap_ra_info(struct vm_fault *vmf,
> atomic_long_set(&vma->swap_readahead_info,
> SWAP_RA_VAL(faddr, win, 0));
>
> - if (win == 1) {
> - pte_unmap(orig_pte);
> + if (win == 1)
> return;
> - }
>
> /* Copy the PTEs because the page table may be unmapped */
> + orig_pte = pte = pte_offset_map(vmf->pmd, faddr);
> if (fpfn == pfn + 1)
> swap_ra_clamp_pfn(vma, faddr, fpfn, fpfn + win, &start, &end);
> else if (pfn == fpfn + 1)