On Mon, Mar 01, 2021 at 02:22:26PM +0800, Muchun Song wrote:
> The remote memcg charing APIs is a mechanism to charge kernel memory
> to a given memcg. So we can move the infrastructure to the scope of
> the CONFIG_MEMCG_KMEM.
This is not a good idea, because there is nothing kmem-specific
in the idea of remote charging, and we definitely will see cases
when user memory is charged to the process different from the current.
>
> As a bonus, on !CONFIG_MEMCG_KMEM build some functions and variables
> can be compiled out.
>
> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> ---
> include/linux/sched.h | 2 ++
> include/linux/sched/mm.h | 2 +-
> kernel/fork.c | 2 +-
> mm/memcontrol.c | 4 ++++
> 4 files changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index ee46f5cab95b..c2d488eddf85 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1314,7 +1314,9 @@ struct task_struct {
>
> /* Number of pages to reclaim on returning to userland: */
> unsigned int memcg_nr_pages_over_high;
> +#endif
>
> +#ifdef CONFIG_MEMCG_KMEM
> /* Used by memcontrol for targeted memcg charge: */
> struct mem_cgroup *active_memcg;
> #endif
> diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
> index 1ae08b8462a4..64a72975270e 100644
> --- a/include/linux/sched/mm.h
> +++ b/include/linux/sched/mm.h
> @@ -294,7 +294,7 @@ static inline void memalloc_nocma_restore(unsigned int flags)
> }
> #endif
>
> -#ifdef CONFIG_MEMCG
> +#ifdef CONFIG_MEMCG_KMEM
> DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
> /**
> * set_active_memcg - Starts the remote memcg charging scope.
> diff --git a/kernel/fork.c b/kernel/fork.c
> index d66cd1014211..d66718bc82d5 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -942,7 +942,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
> tsk->use_memdelay = 0;
> #endif
>
> -#ifdef CONFIG_MEMCG
> +#ifdef CONFIG_MEMCG_KMEM
> tsk->active_memcg = NULL;
> #endif
> return tsk;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 39cb8c5bf8b2..092dc4588b43 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -76,8 +76,10 @@ EXPORT_SYMBOL(memory_cgrp_subsys);
>
> struct mem_cgroup *root_mem_cgroup __read_mostly;
>
> +#ifdef CONFIG_MEMCG_KMEM
> /* Active memory cgroup to use from an interrupt context */
> DEFINE_PER_CPU(struct mem_cgroup *, int_active_memcg);
> +#endif
>
> /* Socket memory accounting disabled? */
> static bool cgroup_memory_nosocket;
> @@ -1054,6 +1056,7 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm)
> }
> EXPORT_SYMBOL(get_mem_cgroup_from_mm);
>
> +#ifdef CONFIG_MEMCG_KMEM
> static __always_inline struct mem_cgroup *active_memcg(void)
> {
> if (in_interrupt())
> @@ -1074,6 +1077,7 @@ static __always_inline bool memcg_kmem_bypass(void)
>
> return false;
> }
> +#endif
>
> /**
> * mem_cgroup_iter - iterate over memory cgroup hierarchy
> --
> 2.11.0
>
