On Monday 18 October 2010 13:37:38 Daniel Lezcano wrote:
> On 10/18/2010 11:54 AM, Hans Schillstrom wrote:
> > On Monday 18 October 2010 10:59:25 Daniel Lezcano wrote:
> >
> >> On 10/08/2010 01:16 PM, Hans Schillstrom wrote:
> >>
> >>> This part contains the include files
> >>> where include/net/netns/ip_vs.h is new and contains all moved vars.
> >>>
> >>> SUMMARY
> >>>
> >>> include/net/ip_vs.h | 136 ++++---
> >>> include/net/net_namespace.h | 2 +
> >>> include/net/netns/ip_vs.h | 112 +++++
> >>>
> >>> Signed-off-by:Hans Schillstrom<hans.schillstrom@xxxxxxxxxxxx>
> >>> ---
> >>>
> >>>
> >>>
> >> [ ... ]
> >>
> >>
> >>> #ifdef CONFIG_IP_VS_IPV6
> >>> diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
> >>> index bd10a79..b59cdc5 100644
> >>> --- a/include/net/net_namespace.h
> >>> +++ b/include/net/net_namespace.h
> >>> @@ -15,6 +15,7 @@
> >>> #include<net/netns/ipv4.h>
> >>> #include<net/netns/ipv6.h>
> >>> #include<net/netns/dccp.h>
> >>> +#include<net/netns/ip_vs.h>
> >>> #include<net/netns/x_tables.h>
> >>> #if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
> >>> #include<net/netns/conntrack.h>
> >>> @@ -91,6 +92,7 @@ struct net {
> >>> struct sk_buff_head wext_nlevents;
> >>> #endif
> >>> struct net_generic *gen;
> >>> + struct netns_ipvs *ipvs;
> >>> };
> >>>
> >>>
> >> IMHO, it would be better to use the net_generic infra-structure instead
> >> of adding a new field in the netns structure.
> >>
> >>
> >>
> > I realized that to, but the performance penalty is quite high with net_generic :-(
> > But on the other hand if you are going to backport it, (without recompiling the kernel)
> > you gonna need it!
> >
>
> Hmm, yes. We don't want to have the init_net_ns performances to be impacted.
>
> You use here a pointer which will be dereferenced like the net_generic,
> I don't think there will be
> a big difference between using net_generic and using a pointer in the
> net namespace structure.
>
> The difference is the id usage, but this one is based on the idr which
> is quite fast.
>
I'm not so sure about that, have a look at net_generic and rcu_read_lock
and compare
ipvs = net->ipvs;
vs.
ipvs = net_generic(net, id)
static inline void *net_generic(struct net *net, int id)
{
struct net_generic *ng;
void *ptr;
rcu_read_lock();
ng = rcu_dereference(net->gen);
BUG_ON(id == 0 || id > ng->len);
ptr = ng->ptr[id - 1];
rcu_read_unlock();
return ptr;
}
...
static inline void rcu_read_lock(void)
{
__rcu_read_lock();
__acquire(RCU);
rcu_read_acquire();
}
Another way of doing it is to pass the ipvs ptr instead of the net ptr,
and add *net to the ipvs struct.
> We should experiment a bit here to compare both solutions.
Agre
>
I single stepped through the rcu_read_lock() on a x86_64
and it's quite many "stepi" that you need to enter :-(
> IMHO, we can (1) create a non-pointer netns_ipvs field in the net
> namespace structure or (2) use a pointer [with net_generic].
>
> (1) is the faster but with the drawback of having a bigger memory
> footprint even if the ipvs module is not loaded.
> In this case we have to take care of what we store in the netns_ipvs
> structure, that is reduce the per namespace table and so. At the first
> glance, I think we can reduce this to the sysctls and a very few data,
> for example using global tables tagged with the namespace and we don't
> break the cacheline alignment optimization.
>
> (2) is slower but as the memory is allocated and freed when the module
> is loaded/unloaded. What I don't like with this approach is we add some
> overhead even if the netns is not compiled in the kernel.
>
or (3)
Like (1) with data that needs to be cache aligned in "struct net"
and the rest in an ipvs struct.
Global hash tables or not ?
> > My sugestion, take both with a configuration switch like:
> > (i.e. avoid the rcu locking)
> >
> > --- net/ip_vs.h ---
> > ...
> > extern int ip_vs_net_id; /* net id for ip_vs */
> >
> >
> > static inline struct netns_ipvs * net_ipvs(struct net* net, int id) {
> > #ifdef CONFIG_IP_VS_FAST_NETNS
> > return net->ipvs;
> > #else
> > return (struct netns_ipvs *)net_generic(net, id);
> > #endif
> > }
> > ...
> >
> > and where you need the netns_ipvs struct ptr,
> > [snip]
> > struct ip_vs_conn *ip_vs_conn_in_get(struct net *net, ....
> > {
> > struct netns_ipvs *ipvs = net_ipvs(net, ip_vs_net_id);
> > ...
> >
>
> It is a nice way to wrap both solutions but at this point I don't think
> it is worth to add a 3rd option to compile ipvs.
>
>
--
Regards
Hans Schillstrom <hans.schillstrom@xxxxxxxxxxxx>
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