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

[Glauber Costa]

On 09/08/2011 02:35 AM, Kirill A. Shutemov wrote:
> On Thu, Sep 08, 2011 at 01:54:03AM -0300, Glauber Costa wrote:
> > On 09/07/2011 07:17 PM, Kirill A. Shutemov wrote:
> > > On Wed, Sep 07, 2011 at 01:23:13AM -0300, Glauber Costa 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
> > >
> > > Will it break something if you define the helpers even if CONFIG_INET
> > > is not defined?
> > > It will be much cleaner. You can reuse ifdef CONFIG_CGROUP_KMEM in this
> > > case.
> >
> > The helpers inside CONFIG_INET are needed for the network code,
> > regardless of kmem cgroup is defined or not, not the other way around.
> >
> > So I could remove CONFIG_INET, but I can't possibly move it inside
> > CONFIG_CGROUP_KMEM. So this buy us nothing.
>
> You can define empty under CONFIG_CGROUP_KMEM's #else, can't you?
> Like with kcg_from_cgroup()/kcg_from_task().
Do you really think it is cleaner?

Why would I define empty something that is not empty at all?
Look again. Most of those helpers would be the exact same with or 
without CONFIG_CGROUP_KMEM . The others, very few differences. If 
CONFIG_INET bothers you, I can remove it altogether, making it 
unconditional. But moving it inside CONFIG_CGROUP_KMEM makes no sense.
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