linux-kernel - Re: [PATCH 1/1] mm: reducing page

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Date:   Tue, 10 Oct 2017 11:34:44 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Ayush Mittal <ayush.m@...sung.com>, akpm@...ux-foundation.org,
        vinmenon@...eaurora.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Cc:     a.sahrawat@...sung.com, pankaj.m@...sung.com, v.narang@...sung.com
Subject: Re: [PATCH 1/1] mm: reducing page_owner structure size

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@...sung.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@...e.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;
>  };
>  
>