[Devel] [PATCH 7/7] packet: Pre-account maximum socket buffer into cg memory (v2)

[Vladimir Davydov]

On Thu, Jun 04, 2015 at 12:47:47PM +0300, Pavel Emelyanov wrote:
> On 06/04/2015 12:02 PM, Vladimir Davydov wrote:
> > On Wed, Jun 03, 2015 at 04:35:35PM +0300, Pavel Emelyanov wrote:
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 4d0a756..45bc78d 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -534,6 +534,20 @@ void sock_update_memcg(struct sock *sk)
> >>  }
> >>  EXPORT_SYMBOL(sock_update_memcg);
> >>  
> >> +struct mem_cgroup *try_get_mem_cgroup_from_current(void)
> >> +{
> >> +	struct mem_cgroup *cg;
> >> +
> >> +	rcu_read_lock();
> >> +	cg = mem_cgroup_from_task(current);
> >> +	if (mem_cgroup_is_root(cg) || !css_tryget(&cg->css))
> >> +		cg = NULL;
> >> +	rcu_read_unlock();
> >> +
> >> +	return cg;
> >> +}
> >> +EXPORT_SYMBOL(try_get_mem_cgroup_from_current);
> >> +
> > 
> > Why not use try_get_mem_cgroup_from_mm(current->mm) instead?
> 
> Because it's stupid, I don't need the steps it does when trying 
> to pick the mm owner in a loop.

Our goal is to reduce churn. In particular, this means reusing existing
functions wherever possible. This particular function does what you need
and there is no point to care if it is stupid or not, just use it :-)
The caller of this function is not in a hot path anyway.