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[PATCH] mm: page_alloc: Remove redundant READ_ONCE

Songtang Liu posted 1 patch 10 months, 1 week ago 
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
[PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Songtang Liu 10 months, 1 week ago 
In the current code, batch is a local variable, and it cannot be
concurrently modified. It's unnecessary to use READ_ONCE here,
so remove it.

Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
Signed-off-by: Songtang Liu <liusongtang@bytedance.com>
---
 mm/page_alloc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e3ea5bf5c459..6edc6e57d4f8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone,
 		free_high = (pcp->free_count >= batch &&
 			     (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
 			     (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
-			      pcp->count >= READ_ONCE(batch)));
+			      pcp->count >= batch));
 		pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
 	} else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
 		pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;
-- 
2.20.1
Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Vishal Moola (Oracle) 10 months, 1 week ago 
On Wed, Apr 02, 2025 at 03:41:16AM -0400, Songtang Liu wrote:
> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
> 
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
> Signed-off-by: Songtang Liu <liusongtang@bytedance.com>

Reviewed-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Oscar Salvador 10 months, 1 week ago 
On Wed, Apr 02, 2025 at 03:41:16AM -0400, Songtang Liu wrote:
> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
> 
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
> Signed-off-by: Songtang Liu <liusongtang@bytedance.com>

Reviewed-by: Oscar Salvador <osalvador@suse.de>


-- 
Oscar Salvador
SUSE Labs
Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Gupta, Pankaj 10 months, 1 week ago 
> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
> 
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
> Signed-off-by: Songtang Liu <liusongtang@bytedance.com>

Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>

> ---
>   mm/page_alloc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e3ea5bf5c459..6edc6e57d4f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone,
>   		free_high = (pcp->free_count >= batch &&
>   			     (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
>   			     (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
> -			      pcp->count >= READ_ONCE(batch)));
> +			      pcp->count >= batch));
>   		pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
>   	} else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
>   		pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;
Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Anshuman Khandual 10 months, 1 week ago 
On 4/2/25 13:11, Songtang Liu wrote:
> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
> 
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")

Although READ_ONCE() should not have been used here with the above
commit - does this cause any problem though ? So in other words is
the Fixes: tag necessary here ?

> Signed-off-by: Songtang Liu <liusongtang@bytedance.com>
> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e3ea5bf5c459..6edc6e57d4f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone,
>  		free_high = (pcp->free_count >= batch &&
>  			     (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
>  			     (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
> -			      pcp->count >= READ_ONCE(batch)));
> +			      pcp->count >= batch));
>  		pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
>  	} else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
>  		pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;

Otherwise LGTM

Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Huang, Ying 10 months, 1 week ago 
Songtang Liu <liusongtang@bytedance.com> writes:

> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
>
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
> Signed-off-by: Songtang Liu <liusongtang@bytedance.com>
> ---
>  mm/page_alloc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e3ea5bf5c459..6edc6e57d4f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone,
>  		free_high = (pcp->free_count >= batch &&
>  			     (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
>  			     (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
> -			      pcp->count >= READ_ONCE(batch)));
> +			      pcp->count >= batch));

Nice catch!

Reviewed-by: Huang Ying <ying.huang@linux.alibaba.com>

>  		pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
>  	} else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
>  		pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;

---
Best Regards,
Huang, Ying
Re: [PATCH] mm: page_alloc: Remove redundant READ_ONCE
Posted by Qi Zheng 10 months, 1 week ago 

On 4/2/25 3:41 PM, Songtang Liu wrote:
> In the current code, batch is a local variable, and it cannot be
> concurrently modified. It's unnecessary to use READ_ONCE here,
> so remove it.
> 
> Fixes: 51a755c56dc0 ("mm: tune PCP high automatically")
> Signed-off-by: Songtang Liu <liusongtang@bytedance.com>
> ---
>   mm/page_alloc.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e3ea5bf5c459..6edc6e57d4f8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2661,7 +2661,7 @@ static void free_frozen_page_commit(struct zone *zone,
>   		free_high = (pcp->free_count >= batch &&
>   			     (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) &&
>   			     (!(pcp->flags & PCPF_FREE_HIGH_BATCH) ||
> -			      pcp->count >= READ_ONCE(batch)));
> +			      pcp->count >= batch));
>   		pcp->flags |= PCPF_PREV_FREE_HIGH_ORDER;
>   	} else if (pcp->flags & PCPF_PREV_FREE_HIGH_ORDER) {
>   		pcp->flags &= ~PCPF_PREV_FREE_HIGH_ORDER;

Reviewed-by: Qi Zheng <zhengqi.arch@bytedance.com>

Thanks!

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