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[Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>]

** Changed in: neutron
       Status: Fix Committed => Fix Released

** Changed in: neutron
    Milestone: None => kilo-2

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https://bugs.launchpad.net/bugs/1390356

Title:
  Improve performance of get_active_networks_info

Status in OpenStack Neutron (virtual network service):
  Fix Released

Bug description:
  When dhcp agent starts, it invokes "get_active_networks_info" rpc to
  get network info. In "get_active_networks_info" function, nested loop
  is used to fill the network structure with subnet and port info, which
  is O(MN) complexity, as showed below:

  for network in networks:
      network['subnets'] = [subnet for subnet in subnets if subnet['network_id'] == network['id']]
      network['ports'] = [port for port in ports if port['network_id'] == network['id']]

  In our all-in-one OpenStack evironment with 4026 networks, 4022
  subnets and 5557 ports, this operation costs 10s!

  I suggest using dictionary to speed up this operation. Building a
  dictionary for networks using id as the key, so each subnet and port
  can be added to the network they belong to without looping the whole
  network list.

  I have written a simple simulation test to compare these two
  approaches(see the attachment). The time cost by the dictionary based
  approach and the original approach are 0.00468s versus 2.95s.
  Considering this function is used in the rpc, this is a significant
  improvement.

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