Comment 6 for bug 1742649

Reviewed: https://review.openstack.org/536959
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=2890d8db67012d7c33c40a1e36a66766740b8f8f
Submitter: Zuul
Branch: master

commit 2890d8db67012d7c33c40a1e36a66766740b8f8f
Author: Matt Riedemann <email address hidden>
Date: Tue Jan 23 15:30:47 2018 -0500

    Expand on when you might want to set --max-count for map_instances

    The default behavior for the "nova-manage cell_v2 map_instances"
    command is to map all instances in the cell in batches of 50.

    This can be slow when there are several thousand instances in the
    deployment and an operator may want to specify a higher --max-count
    value and run the command until it completes.

    This simply updates the command option description and man page to
    point this out for consideration.

    Change-Id: I59c2ed89fe02212977445f6825c6da8fedbb8ccf
    Related-Bug: #1742649