[PATCH net-next 0/4] batch calls to fib_flush and arp_ifdown

fib_flush walks the whole fib in a net_namespace and is called for
each net_device being closed or unregistered. This can be very expensive
when dealing with 100k or more routes in the fib and removal of a lot
of interfaces. These four patches deal with this issue by calling fib_flush
just once for each net namespace and introduce a new function arp_ifdown_all
that does a similar optimization for the neighbour table.

I got the following benchmark results on one of our switches.
Without this patch, deleting 1k interfaces with 100k routes in the fib held
the rtnl_lock for 13 seconds. With the patch, rtnl_lock hold time went down
to 5 seconds. The gain is even more pronounced with 512k routes in the FIB.
In this case, without the patch, rtnl_lock was held for 36 seconds and with
the patch it was held for 5.5 seconds.

Salam Noureddine (4):
  net: add event_list to struct net and provide utility functions
  net: dev: add batching to net_device notifiers
  net: core: introduce neigh_ifdown_all for all down interfaces
  net: fib: avoid calling fib_flush for each device when doing batch
    close     and unregister

 include/linux/netdevice.h   |  2 ++
 include/net/arp.h           |  1 +
 include/net/neighbour.h     |  1 +
 include/net/net_namespace.h | 22 ++++++++++++++++++++++
 include/net/netns/ipv4.h    |  1 +
 net/core/dev.c              | 39 ++++++++++++++++++++++++++++++++++++---
 net/core/neighbour.c        | 38 +++++++++++++++++++++++++++++++-------
 net/ipv4/arp.c              |  4 ++++
 net/ipv4/fib_frontend.c     | 16 ++++++++++++++--
 9 files changed, 112 insertions(+), 12 deletions(-)

-- 
1.8.1.4