Re: [PATCH v8 3/9] socket: initial cgroup code.

[Glauber Costa]

On 12/09/2011 12:05 AM, KAMEZAWA Hiroyuki wrote:
> On Mon,  5 Dec 2011 19:34:57 -0200
> Glauber Costa<glommer@xxxxxxxxxxxxx>  wrote:
>
> > The goal of this work is to move the memory pressure tcp
> > controls to a cgroup, instead of just relying on global
> > conditions.
> >
> > To avoid excessive overhead in the network fast paths,
> > the code that accounts allocated memory to a cgroup is
> > hidden inside a static_branch(). This branch is patched out
> > until the first non-root cgroup is created. So when nobody
> > is using cgroups, even if it is mounted, no significant performance
> > penalty should be seen.
> >
> > This patch handles the generic part of the code, and has nothing
> > tcp-specific.
> >
> > Signed-off-by: Glauber Costa<glommer@xxxxxxxxxxxxx>
> > CC: Kirill A. Shutemov<kirill@xxxxxxxxxxxxx>
> > CC: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxx>
> > CC: David S. Miller<davem@xxxxxxxxxxxxx>
> > CC: Eric W. Biederman<ebiederm@xxxxxxxxxxxx>
> > CC: Eric Dumazet<eric.dumazet@xxxxxxxxx>
>
> I already replied Reviewed-by: but...
Feel free. Reviews, the more, the merrier.

> > +/* Writing them here to avoid exposing memcg's inner layout */
> > +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
> > +#ifdef CONFIG_INET
> > +#include<net/sock.h>
> > +
> > +static bool mem_cgroup_is_root(struct mem_cgroup *memcg);
> > +void sock_update_memcg(struct sock *sk)
> > +{
> > +	/* A socket spends its whole life in the same cgroup */
> > +	if (sk->sk_cgrp) {
> > +		WARN_ON(1);
> > +		return;
> > +	}
> > +	if (static_branch(&memcg_socket_limit_enabled)) {
> > +		struct mem_cgroup *memcg;
> > +
> > +		BUG_ON(!sk->sk_prot->proto_cgroup);
> > +
> > +		rcu_read_lock();
> > +		memcg = mem_cgroup_from_task(current);
> > +		if (!mem_cgroup_is_root(memcg)) {
> > +			mem_cgroup_get(memcg);
> > +			sk->sk_cgrp = sk->sk_prot->proto_cgroup(memcg);
> > +		}
> > +		rcu_read_unlock();
> > +	}
> > +}
>
> Here, you do mem_cgroup_get() if !mem_cgroup_is_root().
>
>
> > +EXPORT_SYMBOL(sock_update_memcg);
> > +
> > +void sock_release_memcg(struct sock *sk)
> > +{
> > +	if (static_branch(&memcg_socket_limit_enabled)&&  sk->sk_cgrp) {
> > +		struct mem_cgroup *memcg;
> > +		WARN_ON(!sk->sk_cgrp->memcg);
> > +		memcg = sk->sk_cgrp->memcg;
> > +		mem_cgroup_put(memcg);
> > +	}
> > +}
>
> You don't check !mem_cgroup_is_root(). Hm, root memcg will not be freed
> by this ?
No, I don't. But I check if sk->sk_cgrp is filled. So it is implied, 
because we only fill in this value if !mem_cgroup_is_root().
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/