[PATCH 1/1] mm: reducing page_owner structure size

[PATCH 1/1] mm: reducing page_owner structure size

[Ayush Mittal]

Maximum page order can be at max 10 which can be accomodated
in short data type(2 bytes).
last_migrate_reason is defined as enum type whose values can
be accomodated in short data type (2 bytes).

Total structure size is currently 16 bytes but after changing structure
size it goes to 12 bytes.

Signed-off-by: Ayush Mittal <ayush.m@samsung.com>
---
 mm/page_owner.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 0fd9dcf..4ab438a 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -19,9 +19,9 @@
 #define PAGE_OWNER_STACK_DEPTH (16)
 
 struct page_owner {
-	unsigned int order;
+	unsigned short order;
+	short last_migrate_reason;
 	gfp_t gfp_mask;
-	int last_migrate_reason;
 	depot_stack_handle_t handle;
 };
 
-- 
1.7.1

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Re: [PATCH 1/1] mm: reducing page_owner structure size

[Vlastimil Babka]

On 10/10/2017 10:25 AM, Ayush Mittal wrote:
> Maximum page order can be at max 10 which can be accomodated
> in short data type(2 bytes).
> last_migrate_reason is defined as enum type whose values can
> be accomodated in short data type (2 bytes).
> 
> Total structure size is currently 16 bytes but after changing structure
> size it goes to 12 bytes.
> 
> Signed-off-by: Ayush Mittal <ayush.m@samsung.com>

Looks like it works, so why not.
Before:
[    0.001000] allocated 50331648 bytes of page_ext
After:
[    0.001000] allocated 41943040 bytes of page_ext

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
>  mm/page_owner.c |    4 ++--
>  1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_owner.c b/mm/page_owner.c
> index 0fd9dcf..4ab438a 100644
> --- a/mm/page_owner.c
> +++ b/mm/page_owner.c
> @@ -19,9 +19,9 @@
>  #define PAGE_OWNER_STACK_DEPTH (16)
>  
>  struct page_owner {
> -	unsigned int order;
> +	unsigned short order;
> +	short last_migrate_reason;
>  	gfp_t gfp_mask;
> -	int last_migrate_reason;
>  	depot_stack_handle_t handle;
>  };
>  
> 

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