Re: [PATCH v4 2/8] socket: initial cgroup code.

Kirill A. Shutemov
2011-10-03T10:47:43Z

On Mon, Oct 03, 2011 at 02:18:37PM +0400, 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@parallels.com>
> CC: David S. Miller <davem@davemloft.net>
> CC: Hiroyouki Kamezawa <kamezawa.hiroyu@jp.fujitsu.com>
> CC: Eric W. Biederman <ebiederm@xmission.com>
> ---
> include/linux/memcontrol.h | 15 +++++++++++++++
> include/net/sock.h | 2 ++
> mm/memcontrol.c | 33 +++++++++++++++++++++++++++++++++
> net/core/sock.c | 3 +++
> 4 files changed, 53 insertions(+), 0 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 3b535db..2cb9226 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -395,5 +395,20 @@ mem_cgroup_print_bad_page(struct page *page)
> }
> #endif
>
> +#ifdef CONFIG_INET
> +struct sock;
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +void sock_update_memcg(struct sock *sk);
> +void sock_release_memcg(struct sock *sk);
> +
> +#else
> +static inline void sock_update_memcg(struct sock *sk)
> +{
> +}
> +static inline void sock_release_memcg(struct sock *sk)
> +{
> +}
> +#endif /* CONFIG_CGROUP_MEM_RES_CTLR_KMEM */
> +#endif /* CONFIG_INET */
> #endif /* _LINUX_MEMCONTROL_H */
>
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 8e4062f..afe1467 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -228,6 +228,7 @@ struct sock_common {
> * @sk_security: used by security modules
> * @sk_mark: generic packet mark
> * @sk_classid: this socket's cgroup classid
> + * @sk_cgrp: this socket's kernel memory (kmem) cgroup
> * @sk_write_pending: a write to stream socket waits to start
> * @sk_state_change: callback to indicate change in the state of the sock
> * @sk_data_ready: callback to indicate there is data to be processed
> @@ -339,6 +340,7 @@ struct sock {
> #endif
> __u32 sk_mark;
> u32 sk_classid;
> + struct mem_cgroup *sk_cgrp;
> void (*sk_state_change)(struct sock *sk);
> void (*sk_data_ready)(struct sock *sk, int bytes);
> void (*sk_write_space)(struct sock *sk);
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 8aaf4ce..08a520e 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -339,6 +339,39 @@ struct mem_cgroup {
> spinlock_t pcp_counter_lock;
> };
>
> +/* Writing them here to avoid exposing memcg's inner layout */
> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> +#ifdef CONFIG_INET
> +#include <net/sock.h>
> +
> +void sock_update_memcg(struct sock *sk)
> +{
> + /* right now a socket spends its whole life in the same cgroup */
> + BUG_ON(sk->sk_cgrp);

Do we really want to panic in this case?

What about WARN() + return?

Otherwise: Acked-by: Kirill A. Shutemov <kirill@shutemov.name>

> +
> + rcu_read_lock();
> + sk->sk_cgrp = mem_cgroup_from_task(current);
> +
> + /*
> + * We don't need to protect against anything task-related, because
> + * we are basically stuck with the sock pointer that won't change,
> + * even if the task that originated the socket changes cgroups.
> + *
> + * What we do have to guarantee, is that the chain leading us to
> + * the top level won't change under our noses. Incrementing the
> + * reference count via cgroup_exclude_rmdir guarantees that.
> + */
> + cgroup_exclude_rmdir(mem_cgroup_css(sk->sk_cgrp));
> + rcu_read_unlock();
> +}

--
Kirill A. Shutemov