Re: [PATCH v3 4/7] per-cgroup tcp buffers control

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Mon, 26 Sep 2011 22:53:05 -0300
Glauber Costa <glommer@parallels.com> wrote:

> On 09/26/2011 07:59 AM, KAMEZAWA Hiroyuki wrote:
> > On Sun, 18 Sep 2011 21:56:42 -0300
> > Glauber Costa<glommer@parallels.com>  wrote:
> >
> >> With all the infrastructure in place, this patch implements
> >> per-cgroup control for tcp memory pressure handling.
> >>
> >> 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>
> >
> > a comment below.
> >
> >> +int tcp_init_cgroup(struct proto *prot, struct cgroup *cgrp,
> >> +		    struct cgroup_subsys *ss)
> >> +{
> >> +	struct mem_cgroup *cg = mem_cgroup_from_cont(cgrp);
> >> +	unsigned long limit;
> >> +
> >> +	cg->tcp_memory_pressure = 0;
> >> +	atomic_long_set(&cg->tcp_memory_allocated, 0);
> >> +	percpu_counter_init(&cg->tcp_sockets_allocated, 0);
> >> +
> >> +	limit = nr_free_buffer_pages() / 8;
> >> +	limit = max(limit, 128UL);
> >> +
> >> +	cg->tcp_prot_mem[0] = sysctl_tcp_mem[0];
> >> +	cg->tcp_prot_mem[1] = sysctl_tcp_mem[1];
> >> +	cg->tcp_prot_mem[2] = sysctl_tcp_mem[2];
> >> +
> >
> > Then, the parameter doesn't inherit parent's one ?
> >
> > I think sockets_populate should pass 'parent' and
> >
> >
> > I think you should have a function
> >
> >      mem_cgroup_should_inherit_parent_settings(parent)
> >
> > (This is because you made this feature as a part of memcg.
> >   please provide expected behavior.)
> >
> > Thanks,
> > -Kame
> 
> Kame: Another look into this:
> 
> sysctl_tcp_mem is a global value, unless you have different namespaces.
> So it is either global anyway, or should come from the namespace, not 
> the parent.
> 
> Now, the goal here is to set the maximum possible value for those 
> fields. That, indeed, should come from the parent.
> 
> That's my understanding...
> 
Hmm, I may misunderstand something. If this isn't a value you don't want to limit
by memcg's kmem_limit, it's ok.
Maybe memcg should just take care of kmem_limit.

Thanks,
-Kame





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