Re: [PATCH v2 3/9] socket: initial cgroup code.

[Glauber Costa]

On 09/07/2011 02:26 AM, Paul Menage wrote:
> On Tue, Sep 6, 2011 at 9:23 PM, Glauber Costa<glommer@xxxxxxxxxxxxx>  wrote:
> > We aim to control the amount of kernel memory pinned at any
> > time by tcp sockets. To lay the foundations for this work,
> > this patch adds a pointer to the kmem_cgroup to the socket
> > structure.
> >
> > Signed-off-by: Glauber Costa<glommer@xxxxxxxxxxxxx>
> > CC: David S. Miller<davem@xxxxxxxxxxxxx>
> > CC: Hiroyouki Kamezawa<kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > CC: Eric W. Biederman<ebiederm@xxxxxxxxxxxx>
> > ---
> >   include/linux/kmem_cgroup.h |   29 +++++++++++++++++++++++++++++
> >   include/net/sock.h          |    2 ++
> >   net/core/sock.c             |    5 ++---
> >   3 files changed, 33 insertions(+), 3 deletions(-)
> >
> > diff --git a/include/linux/kmem_cgroup.h b/include/linux/kmem_cgroup.h
> > index 0e4a74b..77076d8 100644
> > --- a/include/linux/kmem_cgroup.h
> > +++ b/include/linux/kmem_cgroup.h
> > @@ -49,5 +49,34 @@ static inline struct kmem_cgroup *kcg_from_task(struct task_struct *tsk)
> >         return NULL;
> >   }
> >   #endif /* CONFIG_CGROUP_KMEM */
> > +
> > +#ifdef CONFIG_INET
> > +#include<net/sock.h>
> > +static inline void sock_update_kmem_cgrp(struct sock *sk)
> > +{
> > +#ifdef CONFIG_CGROUP_KMEM
> > +       sk->sk_cgrp = kcg_from_task(current);
>
> BUG_ON(sk->sk_cgrp) ? Or else release the old cgroup if necessary.

Since at least in this current incarnation, I am not doing migrations,
I definitely don't expect to have a pointer already present here.
BUG_ON() it is.

> > @@ -339,6 +340,7 @@ struct sock {
> >   #endif
> >         __u32                   sk_mark;
> >         u32                     sk_classid;
> > +       struct kmem_cgroup      *sk_cgrp;
>
> Should this be protected by a #ifdef?
I don't particularly like it. I think that ifdef'ing fields
in structures, while allowing for size optimization, takes away
size and alignment predictability. But... can do.
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