Reviewed: https://review.openstack.org/588665
Committed:
https://git.openstack.org/cgit/openstack/nova/commit/?id=27857c337378472205c37db6ab79fe8404406129
Submitter: Zuul
Branch: master
commit 27857c337378472205c37db6ab79fe8404406129
Author: Matt Riedemann <mriedem...@gmail.com>
Date: Fri Aug 3 17:26:00 2018 -0400
Optimize AZ lookup during schedule_and_build_instances
If we're creating multiple servers, there is a chance
the scheduler returned the same host for more than
one of them, which means we could be redundantly
looking up the AZ for the same host multiple times.
This could happen when creating multiple servers in
the same strict affinity group, or simply if the
scheduler is configured with a pack-first strategy
for filling up hosts. The get_host_availability_zone()
method does not use its own internal cache, so this
change adds a simple cache to the schedule_and_build_instances
method itself so that we only lookup the AZ per unique
host once.
Note that build_instances suffers from the same issue
but that is only called for scheduling with cells v1
which is deprecated so we shouldn't need to care about
optimizing that method.
Change-Id: I2ae5ae7240e5183acca7492ddad017c0c878835b
Closes-Bug: #1785327
** Changed in: nova
Status: In Progress => Fix Released
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https://bugs.launchpad.net/bugs/1785327
Title:
schedule_and_build_instances looks up host az for every instance even
if using the same host
Status in OpenStack Compute (nova):
Fix Released
Status in OpenStack Compute (nova) pike series:
Confirmed
Status in OpenStack Compute (nova) queens series:
Confirmed
Bug description:
This is a simple performance optimization bug. When creating multiple
servers, if they are in an affinity group they are going to be on the
same host. Or if simply the scheduler configuration is such that
instances are packed onto as few hosts as possible rather than spread,
the scheduler could return several of the same hosts for the list of
instances being scheduled. We iterate over the instances and their
selected hosts and we lookup the az for each host in the loop which is
a query to the aggregates table in the API DB. If we have >1 of the
same host in the list, we could optimize this by simply caching the
host=az mapping.
https://github.com/openstack/nova/blob/4c37ff72e5446c835a48d569dd5a1416fcd36c71/nova/conductor/manager.py#L1263
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