Re: [PATCH v4 1/5] mm/memcg: Move mod_objcg_state() to memcontrol.c

[Waiman Long]

On 4/19/21 1:19 PM, Waiman Long wrote:
> On 4/19/21 1:13 PM, Johannes Weiner wrote:
> > On Mon, Apr 19, 2021 at 12:18:29PM -0400, Waiman Long wrote:
> > > On 4/19/21 11:21 AM, Waiman Long wrote:
> > > > On 4/19/21 11:14 AM, Johannes Weiner wrote:
> > > > > On Sun, Apr 18, 2021 at 08:00:28PM -0400, Waiman Long wrote:
> > > > > > The mod_objcg_state() function is moved from mm/slab.h to
> > > > > > mm/memcontrol.c
> > > > > > so that further optimization can be done to it in later patches 
> > > > > > without
> > > > > > exposing unnecessary details to other mm components.
> > > > > >
> > > > > > Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> > > > > > ---
> > > > > >    mm/memcontrol.c | 13 +++++++++++++
> > > > > >    mm/slab.h       | 16 ++--------------
> > > > > >    2 files changed, 15 insertions(+), 14 deletions(-)
> > > > > >
> > > > > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > > > > > index e064ac0d850a..dc9032f28f2e 100644
> > > > > > --- a/mm/memcontrol.c
> > > > > > +++ b/mm/memcontrol.c
> > > > > > @@ -3150,6 +3150,19 @@ void __memcg_kmem_uncharge_page(struct
> > > > > > page *page, int order)
> > > > > >        css_put(&memcg->css);
> > > > > >    }
> > > > > >    +void mod_objcg_state(struct obj_cgroup *objcg, struct
> > > > > > pglist_data *pgdat,
> > > > > > +             enum node_stat_item idx, int nr)
> > > > > > +{
> > > > > > +    struct mem_cgroup *memcg;
> > > > > > +    struct lruvec *lruvec = NULL;
> > > > > > +
> > > > > > +    rcu_read_lock();
> > > > > > +    memcg = obj_cgroup_memcg(objcg);
> > > > > > +    lruvec = mem_cgroup_lruvec(memcg, pgdat);
> > > > > > +    mod_memcg_lruvec_state(lruvec, idx, nr);
> > > > > > +    rcu_read_unlock();
> > > > > > +}
> > > > > It would be more naturally placed next to the others, e.g. below
> > > > > __mod_lruvec_kmem_state().
> > > > >
> > > > > But no deal breaker if there isn't another revision.
> > > > >
> > > > > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> > > > Yes, there will be another revision by rebasing patch series on the
> > > > linux-next. I will move the function then.
> > > OK, it turns out that mod_objcg_state() is only defined if
> > > CONFIG_MEMCG_KMEM. That was why I put it in the CONFIG_MEMCG_KMEM 
> > > block with
> > > the other obj_stock functions. I think I will keep it there.
> > The CONFIG_MEMCG_KMEM has become sort of useless now. It used to be
> > configurable, but now it just means CONFIG_MEMCG && !CONFIG_SLOB. And
> > even that doesn't make sense because while slob doesn't support slab
> > object tracking, we can still do all the other stuff we do under
> > KMEM. I have a patch in the works to remove the symbol and ifdefs.
> >
> > With that in mind, it's better to group the functions based on what
> > they do rather than based on CONFIG_MEMCG_KMEM. It's easier to just
> > remove another ifdef later than it is to reorder the functions.
> OK, I will make the move then. Thanks for the explanation. 

BTW, have you ever thought of moving the cgroup-v1 specific functions 
out into a separate memcontrol-v1.c file just like 
kernel/cgroup/cgroup-v1.c?

I thought of that before, but memcontrol.c is a frequently changed file 
and so a bit hard to do.

Cheers,
Longman