How to configure swap for overcloud nodes

Solution Unverified - Updated

Environment

  • Red Hat OpenStack Platform 13

Issue

  • How can we configure swap for all overcloud nodes?

Resolution

  • There are two options available

  • To have independent partition for swap

    • Recreate flavours for overcloud roles with adding swap amount, before you run before deploying overcloud
$ source ~/stackrc
$ openstack flavor delete control
$ openstack flavor create --ram 4096 --vcpus 1 --disk 40 --swap 10 \
  --property resources:CUSTOM_BAREMETAL=1 --property resources:DISK_GB=0 \
  --property resources:MEMORY_MB=0 --property resources:VCPU=0 --property capabilities:boot_option=local \
  --property capabilities:profile=control control
  • Specify the template file to enable swap in openstack overcloud deploy
$ openstack overcloud deploy --templates \
...
-e /usr/share/openstack-tripleo-heat-templates/environments/enable-swap-partition.yaml
  • To have "/swap" file on root file system and use it as loopback swap device
    • Include the following tememplate in openstack overcloud deploy

 $ openstack overcloud deploy --templates \
 ...
 -e /usr/share/openstack-tripleo-heat-templates/environments/enable-swap.yaml
  • swap_size_megabytes should be set in the templates to have expected size of swap
  swap_size_megabytes:
    type: string
    description: Amount of swap space to allocate in megabytes
    default: '4096'

Root Cause

  • Ironic creates a swap partition with the label "swap1" when it launch a baremetal instance with the flavour which has swap amount configured

Diagnostic Steps

WARNING When creating a swap partition on a compute node, it's possible that operations that maps a large amount of memory hitting the swap can kill the I/O of the block device. For example, when spawning an SR-IOV instance, qemu will map all the RAM assigned to the instance. If most of this RAM would hit the swap, it might cause a system lock up on the compute node. See this This content is not included.bugzilla for more information.

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