* Re: [PATCH] mm/swap_state: Skip meaningless swap cache readahead when ra_info.win == 0
@ 2020-10-26 2:46 linmiaohe
0 siblings, 0 replies; 3+ messages in thread
From: linmiaohe @ 2020-10-26 2:46 UTC (permalink / raw)
To: Andrew Morton; +Cc: linux-mm, linux-kernel, Hugh Dickins
Andrew Morton <akpm@linux-foundation.org> wrote:
> On Fri, 9 Oct 2020 09:30:59 -0400 Miaohe Lin <linmiaohe@huawei.com> wrote:
>
>> swap_ra_info() may leave ra_info untouched in non_swap_entry() case as
>> page table lock is not held. In this case, we have ra_info.nr_pte == 0
>> and it is meaningless to continue with swap cache readahead. Skip such
>> ops by init ra_info.win = 1.
>>
>
>Looks right. But I think it would be better to fix this in
>swap_ra_info() - make it more consistent in its return state.
>
I think modernify the struct initializer is better because it means we have to swap in one page at least.
Many thanks.
>Otherwise, let's modernify that struct initializer:
>
>--- a/mm/swap_state.c~mm-swap_state-skip-meaningless-swap-cache-readahead-when-ra_infowin-==-0-fix
>+++ a/mm/swap_state.c
>@@ -839,7 +839,9 @@ static struct page *swap_vma_readahead(s
> swp_entry_t entry;
> unsigned int i;
> bool page_allocated;
>- struct vma_swap_readahead ra_info = {1,};
>+ struct vma_swap_readahead ra_info = {
>+ .win = 1,
>+ };
>
> swap_ra_info(vmf, &ra_info);
> if (ra_info.win == 1)
>_
>
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH] mm/swap_state: Skip meaningless swap cache readahead when ra_info.win == 0
@ 2020-10-09 13:30 Miaohe Lin
2020-10-25 23:59 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Miaohe Lin @ 2020-10-09 13:30 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, linmiaohe
swap_ra_info() may leave ra_info untouched in non_swap_entry() case as page
table lock is not held. In this case, we have ra_info.nr_pte == 0 and it is
meaningless to continue with swap cache readahead. Skip such ops by init
ra_info.win = 1.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/swap_state.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index ee465827420e..b9013c3f94c9 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -839,7 +839,7 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
swp_entry_t entry;
unsigned int i;
bool page_allocated;
- struct vma_swap_readahead ra_info = {0,};
+ struct vma_swap_readahead ra_info = {1,};
swap_ra_info(vmf, &ra_info);
if (ra_info.win == 1)
--
2.19.1
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] mm/swap_state: Skip meaningless swap cache readahead when ra_info.win == 0
2020-10-09 13:30 Miaohe Lin
@ 2020-10-25 23:59 ` Andrew Morton
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Morton @ 2020-10-25 23:59 UTC (permalink / raw)
To: Miaohe Lin; +Cc: linux-mm, linux-kernel, Hugh Dickins
On Fri, 9 Oct 2020 09:30:59 -0400 Miaohe Lin <linmiaohe@huawei.com> wrote:
> swap_ra_info() may leave ra_info untouched in non_swap_entry() case as page
> table lock is not held. In this case, we have ra_info.nr_pte == 0 and it is
> meaningless to continue with swap cache readahead. Skip such ops by init
> ra_info.win = 1.
>
>
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -839,7 +839,7 @@ static struct page *swap_vma_readahead(swp_entry_t fentry, gfp_t gfp_mask,
> swp_entry_t entry;
> unsigned int i;
> bool page_allocated;
> - struct vma_swap_readahead ra_info = {0,};
> + struct vma_swap_readahead ra_info = {1,};
>
> swap_ra_info(vmf, &ra_info);
> if (ra_info.win == 1)
Looks right. But I think it would be better to fix this in
swap_ra_info() - make it more consistent in its return state.
Otherwise, let's modernify that struct initializer:
--- a/mm/swap_state.c~mm-swap_state-skip-meaningless-swap-cache-readahead-when-ra_infowin-==-0-fix
+++ a/mm/swap_state.c
@@ -839,7 +839,9 @@ static struct page *swap_vma_readahead(s
swp_entry_t entry;
unsigned int i;
bool page_allocated;
- struct vma_swap_readahead ra_info = {1,};
+ struct vma_swap_readahead ra_info = {
+ .win = 1,
+ };
swap_ra_info(vmf, &ra_info);
if (ra_info.win == 1)
_
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-10-25 23:59 ` Andrew Morton
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