From: Shakeel Butt <shakeel.butt@linux.dev>
To: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
cgroups@vger.kernel.org, linux-mm@kvack.org,
Axel Rasmussen <axelrasmussen@google.com>
Subject: Re: [PATCH 3/3] ptdesc: Account page tables to memcgs again
Date: Wed, 25 Feb 2026 08:55:54 -0800 [thread overview]
Message-ID: <aZ8oT-n4a8VDY2AH@linux.dev> (raw)
In-Reply-To: <20260225162319.315281-4-willy@infradead.org>
On Wed, Feb 25, 2026 at 04:22:17PM +0000, Matthew Wilcox (Oracle) wrote:
> Commit f0c92726e89f removed the accounting of page tables to memcgs.
> Reintroduce it.
>
> Fixes: f0c92726e89f (ptdesc: remove references to folios from __pagetable_ctor() and pagetable_dtor())
> Reported-by: Axel Rasmussen <axelrasmussen@google.com>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> include/linux/mm.h | 15 +++++++++++++--
> include/linux/mm_types.h | 6 +++---
> 2 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 5be3d8a8f806..34bc6f00ed7b 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3519,21 +3519,32 @@ static inline unsigned long ptdesc_nr_pages(const struct ptdesc *ptdesc)
> return compound_nr(ptdesc_page(ptdesc));
> }
>
> +static inline struct mem_cgroup *pagetable_memcg(const struct ptdesc *ptdesc)
> +{
> +#ifdef CONFIG_MEMCG
> + return ptdesc->pt_memcg;
> +#else
> + return NULL;
> +#endif
> +}
> +
> static inline void __pagetable_ctor(struct ptdesc *ptdesc)
> {
> pg_data_t *pgdat = NODE_DATA(memdesc_nid(ptdesc->pt_flags));
> + struct mem_cgroup *memcg = pagetable_memcg(ptdesc);
>
> __SetPageTable(ptdesc_page(ptdesc));
> - mod_node_page_state(pgdat, NR_PAGETABLE, ptdesc_nr_pages(ptdesc));
> + memcg_stat_mod(memcg, pgdat, NR_PAGETABLE, ptdesc_nr_pages(ptdesc));
> }
>
> static inline void pagetable_dtor(struct ptdesc *ptdesc)
> {
> pg_data_t *pgdat = NODE_DATA(memdesc_nid(ptdesc->pt_flags));
> + struct mem_cgroup *memcg = pagetable_memcg(ptdesc);
>
> ptlock_free(ptdesc);
> __ClearPageTable(ptdesc_page(ptdesc));
> - mod_node_page_state(pgdat, NR_PAGETABLE, -ptdesc_nr_pages(ptdesc));
> + memcg_stat_mod(memcg, pgdat, NR_PAGETABLE, -ptdesc_nr_pages(ptdesc));
> }
>
> static inline void pagetable_dtor_free(struct ptdesc *ptdesc)
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index 3cc8ae722886..e9b1da04938a 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -564,7 +564,7 @@ FOLIO_MATCH(compound_head, _head_3);
> * @ptl: Lock for the page table.
> * @__page_type: Same as page->page_type. Unused for page tables.
> * @__page_refcount: Same as page refcount.
> - * @pt_memcg_data: Memcg data. Tracked for page tables here.
> + * @pt_memcg: Memcg that this page table belongs to.
> *
> * This struct overlays struct page for now. Do not modify without a good
> * understanding of the issues.
> @@ -602,7 +602,7 @@ struct ptdesc {
> unsigned int __page_type;
> atomic_t __page_refcount;
> #ifdef CONFIG_MEMCG
> - unsigned long pt_memcg_data;
> + struct mem_cgroup *pt_memcg;
This is kernel memory, so this would be struct obj_cgroup * instead of struct
mem_cgroup pointer. We will need something similar to __folio_objcg(), maybe
__ptdesc_objcg() and then call obj_cgroup_memcg() on it. Basically how
folio_memcg() handles the kernel memory.
prev parent reply other threads:[~2026-02-25 16:56 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-25 16:22 [PATCH 0/3] Make memcg location more flexible Matthew Wilcox (Oracle)
2026-02-25 16:22 ` [PATCH 1/3] memcg: Add memcg_stat_mod() Matthew Wilcox (Oracle)
2026-02-25 19:22 ` Johannes Weiner
2026-02-25 16:22 ` [PATCH 2/3] memcg: Simplify mod_lruvec_kmem_state() Matthew Wilcox (Oracle)
2026-02-25 16:22 ` [PATCH 3/3] ptdesc: Account page tables to memcgs again Matthew Wilcox (Oracle)
2026-02-25 16:55 ` Shakeel Butt [this message]
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