On Fri, 2016-07-08 at 13:07 +0200, Thomas Graf wrote:
> On 07/07/16 at 10:36pm, Jiri Kosina wrote:
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index f45929c..630838e 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -52,6 +52,7 @@
> > #include <uapi/linux/netdevice.h>
> > #include <uapi/linux/if_bonding.h>
> > #include <uapi/linux/pkt_cls.h>
> > +#include <linux/hashtable.h>
> >
> > struct netpoll_info;
> > struct device;
> > @@ -1778,6 +1779,7 @@ struct net_device {
> > unsigned int num_tx_queues;
> > unsigned int real_num_tx_queues;
> > struct Qdisc *qdisc;
> > + DECLARE_HASHTABLE (qdisc_hash, 16);
>
> This blows up net_device to an insane size: 64K * sizeof(struct
> hlist_head). Can we allocate this on demand for net_devices where
> it is actually needed? The majority of virtual devices won't need
> this. Doesn't have to be rhashtable, can still be fixed size but
> at least allocate it.
Jiri probably misread the API and should have used :
DECLARE_HASHTABLE (qdisc_hash, 4);
Google has a very similar patch with 16 buckets, and it is 'good enough',
although we do not hit the qdisc_tree_reduce_backlog() penalty.
