yahoo-eng-team team mailing list archive

[Sahid Orentino <1959750@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

During some investigations regarding segments we may have noticed
performance issues related to the current algorithm that schedules
network segments on hosts.

When an agent is reporting a change in segment, the process goes to the
function `auto_schedule_new_network_segments` with the list of the
segments that this host handles.

This function is retrieving from the segments the related networks, then
we can notice that the algorithm is running a double for loop. That one
iterates through network and per segments to schedule network segments
on all hosts.

        for network_id in network_ids:
            for segment in segments:
                self._schedule_network(
                    payload.context, network_id, dhcp_notifier,
                        candidate_hosts=segment['hosts'])

Depending on the design chosen, in a setup that has hundred segments per
host with hundred networks and potentially segments that share the same
list of hosts, we will endup by calling _schedule_network 10000 times
with duplication.

To avoid such duplication and unnecessary calls of _schedule_network for
the same hosts we may want to provide a datastructure that is storing
for each network the hosts already scheduled.

     for network_id in network_ids:
         for segment in segments:
             if not _already_scheduled(network_id, segment['hosts']):
                 self._schedule_network(
                     payload.context, network_id, dhcp_notifier,
                     candidate_hosts=segment['hosts'])

With this same scenario, and by using such algorithm we may reduce the
number of call per the number of networks, 100.

Thanks,
s.

** Affects: neutron
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1959750

Title:
  potential performance issue when scheduling network segments

Status in neutron:
  New

Bug description:
  During some investigations regarding segments we may have noticed
  performance issues related to the current algorithm that schedules
  network segments on hosts.

  When an agent is reporting a change in segment, the process goes to
  the function `auto_schedule_new_network_segments` with the list of the
  segments that this host handles.

  This function is retrieving from the segments the related networks,
  then we can notice that the algorithm is running a double for loop.
  That one iterates through network and per segments to schedule network
  segments on all hosts.

          for network_id in network_ids:
              for segment in segments:
                  self._schedule_network(
                      payload.context, network_id, dhcp_notifier,
                          candidate_hosts=segment['hosts'])

  Depending on the design chosen, in a setup that has hundred segments
  per host with hundred networks and potentially segments that share the
  same list of hosts, we will endup by calling _schedule_network 10000
  times with duplication.

  To avoid such duplication and unnecessary calls of _schedule_network
  for the same hosts we may want to provide a datastructure that is
  storing for each network the hosts already scheduled.

       for network_id in network_ids:
           for segment in segments:
               if not _already_scheduled(network_id, segment['hosts']):
                   self._schedule_network(
                       payload.context, network_id, dhcp_notifier,
                       candidate_hosts=segment['hosts'])

  With this same scenario, and by using such algorithm we may reduce the
  number of call per the number of networks, 100.

  Thanks,
  s.

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