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SubjectRe: [PATCH -V8 10/16] hugetlb/cgroup: Add the cgroup pointer to page lru
Date
Michal Hocko <mhocko@suse.cz> writes:

> On Sat 09-06-12 14:29:55, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>>
>> Add the hugetlb cgroup pointer to 3rd page lru.next.
>
> Interesting and I really like the idea much more than tracking by
> page_cgroup.
>
>> This limit the usage to hugetlb cgroup to only hugepages with 3 or
>> more normal pages. I guess that is an acceptable limitation.
>
> Agreed.
>
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
>
> Other than some nits I like this.
> Thanks!
>
>> ---
>> 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)
>
> Why 3? I think you wanted 2 here, right?

Yes that should be 2. I updated that in an earlier. Already in v9
version I have locally.

>
>> + return NULL;
>> + return (struct hugetlb_cgroup *)page[2].lru.next;
>> +}
>> +
>> +static inline
>> +int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
>> +{
>> + if (!PageHuge(page))
>> + return -1;
>> + if (compound_order(page) < 3)
>
> Here as well.
>
>> + 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));
>
> What about VM_BUG_ON?

Will do, So when do one decide to choose VM_BUG_ON against BUG_ON ?

>
>> 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);
>
> Why inside the spin lock?

All page[2].lru.next update is protected by hugetlb_lock . It should not
really matter here, because the pages are not yet available to use.

>
>> 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
>> */
>> --

-aneesh



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