linux-kernel - Re: [PATCH 1/3] mm/page_alloc: factor out setting of pcp->high and pcp->batch.

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Date:	Sun, 07 Apr 2013 09:37:28 +0800
From:	Simon Jeons <simon.jeons@...il.com>
To:	Cody P Schafer <cody@...ux.vnet.ibm.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>, Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] mm/page_alloc: factor out setting of pcp->high and
 pcp->batch.

Hi Cody,
On 04/06/2013 04:33 AM, Cody P Schafer wrote:
> Creates pageset_set_batch() for use in setup_pageset().
> pageset_set_batch() imitates the functionality of
> setup_pagelist_highmark(), but uses the boot time
> (percpu_pagelist_fraction == 0) calculations for determining ->high

Why need adjust pcp->high, pcp->batch during system running? What's the 
requirement?

> based on ->batch.
>
> Signed-off-by: Cody P Schafer <cody@...ux.vnet.ibm.com>
> ---
>   mm/page_alloc.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 8fcced7..5877cf0 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4004,6 +4004,14 @@ static int __meminit zone_batchsize(struct zone *zone)
>   #endif
>   }
>   
> +/* a companion to setup_pagelist_highmark() */
> +static void pageset_set_batch(struct per_cpu_pageset *p, unsigned long batch)
> +{
> +	struct per_cpu_pages *pcp = &p->pcp;
> +	pcp->high = 6 * batch;
> +	pcp->batch = max(1UL, 1 * batch);
> +}
> +
>   static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
>   {
>   	struct per_cpu_pages *pcp;
> @@ -4013,8 +4021,7 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
>   
>   	pcp = &p->pcp;
>   	pcp->count = 0;
> -	pcp->high = 6 * batch;
> -	pcp->batch = max(1UL, 1 * batch);
> +	pageset_set_batch(p, batch);
>   	for (migratetype = 0; migratetype < MIGRATE_PCPTYPES; migratetype++)
>   		INIT_LIST_HEAD(&pcp->lists[migratetype]);
>   }
> @@ -4023,7 +4030,6 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch)
>    * setup_pagelist_highmark() sets the high water mark for hot per_cpu_pagelist
>    * to the value high for the pageset p.
>    */
> -
>   static void setup_pagelist_highmark(struct per_cpu_pageset *p,
>   				unsigned long high)
>   {

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