On Tue, Mar 2, 2021 at 9:15 AM Roman Gushchin <g...@fb.com> wrote:
>
> 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.
Got it. Thanks for your reminder.
>
> >
> > As a bonus, on !CONFIG_MEMCG_KMEM build some functions and variables
> > can be compiled out.
> >
> > Signed-off-by: Muchun Song <songmuc...@bytedance.com>
> > ---
> > 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
> >
