linux-kernel - Re: [PATCH -V8 10/16] hugetlb/cgroup: Add the cgroup pointer to page lru

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Date:	Mon, 11 Jun 2012 17:41:38 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC:	linux-mm@...ck.org, dhillf@...il.com, rientjes@...gle.com,
	mhocko@...e.cz, akpm@...ux-foundation.org, hannes@...xchg.org,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [PATCH -V8 10/16] hugetlb/cgroup: Add the cgroup pointer to page
 lru

(2012/06/09 17:59), Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V"<aneesh.kumar@...ux.vnet.ibm.com>
> 
> Add the hugetlb cgroup pointer to 3rd page lru.next. This limit
> the usage to hugetlb cgroup to only hugepages with 3 or more
> normal pages. I guess that is an acceptable limitation.
> 
> Signed-off-by: Aneesh Kumar K.V<aneesh.kumar@...ux.vnet.ibm.com>


This approach seems much better than using page_cgroup.



> ---
>   include/linux/hugetlb_cgroup.h |   31 +++++++++++++++++++++++++++++++
>   mm/hugetlb.c                   |    4 ++++
>   2 files changed, 35 insertions(+)
> 
> diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
> index 5794be4..ceff1d5 100644
> --- a/include/linux/hugetlb_cgroup.h
> +++ b/include/linux/hugetlb_cgroup.h
> @@ -26,6 +26,26 @@ struct hugetlb_cgroup {
>   };
> 
>   #ifdef CONFIG_CGROUP_HUGETLB_RES_CTLR
> +static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
> +{
> +	if (!PageHuge(page))
> +		return NULL;
> +	if (compound_order(page)<  3)
> +		return NULL;
> +	return (struct hugetlb_cgroup *)page[2].lru.next;
> +}

As pointed out by Michal, you can have 4pages with order=2.

Thanks,
-Kame

> +
> +static inline
> +int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
> +{
> +	if (!PageHuge(page))
> +		return -1;
> +	if (compound_order(page)<  3)
> +		return -1;
> +	page[2].lru.next = (void *)h_cg;
> +	return 0;
> +}
> +
>   static inline bool hugetlb_cgroup_disabled(void)
>   {
>   	if (hugetlb_subsys.disabled)
> @@ -43,6 +63,17 @@ extern void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
>   extern void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
>   					   struct hugetlb_cgroup *h_cg);
>   #else
> +static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
> +{
> +	return NULL;
> +}
> +
> +static inline
> +int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
> +{
> +	return 0;
> +}
> +
>   static inline bool hugetlb_cgroup_disabled(void)
>   {
>   	return true;
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index e899a2d..1ca2d8f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -28,6 +28,7 @@
> 
>   #include<linux/io.h>
>   #include<linux/hugetlb.h>
> +#include<linux/hugetlb_cgroup.h>
>   #include<linux/node.h>
>   #include "internal.h"
> 
> @@ -591,6 +592,7 @@ static void update_and_free_page(struct hstate *h, struct page *page)
>   				1<<  PG_active | 1<<  PG_reserved |
>   				1<<  PG_private | 1<<  PG_writeback);
>   	}
> +	BUG_ON(hugetlb_cgroup_from_page(page));
>   	set_compound_page_dtor(page, NULL);
>   	set_page_refcounted(page);
>   	arch_release_hugepage(page);
> @@ -643,6 +645,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
>   	INIT_LIST_HEAD(&page->lru);
>   	set_compound_page_dtor(page, free_huge_page);
>   	spin_lock(&hugetlb_lock);
> +	set_hugetlb_cgroup(page, NULL);
>   	h->nr_huge_pages++;
>   	h->nr_huge_pages_node[nid]++;
>   	spin_unlock(&hugetlb_lock);
> @@ -892,6 +895,7 @@ static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
>   		INIT_LIST_HEAD(&page->lru);
>   		r_nid = page_to_nid(page);
>   		set_compound_page_dtor(page, free_huge_page);
> +		set_hugetlb_cgroup(page, NULL);
>   		/*
>   		 * We incremented the global counters already
>   		 */


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