SPDX-License-Identifier: Apache-2.0
Copyright (c) 2019-2020 Intel Corporation

HugePage support in OpenNESS

Overview

Memory is allocated to application processes in terms of pages and by default, 4K pages are supported. For applications dealing with larger datasets, using 4K pages may lead to performance degradation and overhead because of translation lookaside buffer (TLB) misses. To address this, modern CPUs support HugePages which are typically 2M and 1G. This helps avoid TLB miss overhead and therefore improves performance.

Both applications and network functions can improve performance using HugePages. Huge page support, added to Kubernetes* v1.8, enables the discovery, scheduling, and allocation of huge pages as a native, first-class resource. This support addresses low latency and deterministic memory access requirements.

Details of HugePage support on OpenNESS

Deployment of OpenNESS’ minimal flavor does not enable the hugepages. To enable hugepages either use flavor that supports hugepages (e.g. flexran) or enable hugepages by editing default_grub_params variable in group_vars and/or host_vars. Suggested value for hugepage enablement is default_hugepagesz= hugepagesz= hugepages=.

Next, following parameters can be used for tuning hugepages:

  • hugepage_size - size, which can be either 2M or 1G
  • hugepage_amount - amount

Previously default values were: | Machine type | hugepage_amount | hugepage_size | |————–|——————-|—————–| | Controller | 1024 | 2M | | Node | 1024 | 2M |

Find below a guide on changing these values. Customizations must be made before OpenNESS deployment.

Variables for hugepage customization can be placed in several files:

  • inventory/default/group_vars/controller_group/10-default.yml and inventory/default/group_vars/edgenode_group/10-default.yml will affect Edge Controller and Edge Nodes
  • inventory/default/host_vars/<inventory_host_name>/10-default.yml will only affect the <inventory_host_name> host present in inventory.yml
  • Hugepages can be also specified inside playbook, however due to Ansible’s* variable priority this is not recommended (it will override both group_vars and host_vars). For example:
    # network_edge.yml
    
    - hosts: edgenode_group
      vars:
        hugepage_amount: "5000"
    

    The usage is summarized in the following table:

File Edge Controller Edge Node Comment
inventory/default/group_vars/controller_group/10-default.yml yes    
inventory/default/group_vars/edgenode_group/10-default.yml   yes - every node  
inventory/default/host_vars/<inventory_host_name>/10-default.yml yes yes affects machine specified in inventory.yml with name <inventory_host_name>
network_edge.yml vars under hosts: controller_group vars under hosts: edgenode_group - every node not recommended

Note that variables have precedence:

  1. not recommended: network_edge.yml will always take precedence for files from this list (overrides every other var)
  2. inventory/default/host_vars/
  3. inventory/default/group_vars/edgenode_group/10-default.yml and inventory/default/group_vars/controller_group/10-default.yml
  4. inventory/default/group_vars/all/10-default.yml
  5. default/main.yml in roles’ directory

Examples

Changing size and amount of the hugepages for both controller and nodes

Change the following lines in the inventory/default/group_vars/edgenode_group/10-default.yml or inventory/default/group_vars/controller_group/10-default.yml:

  • To set 1500 of the hugepages with the page size of 2 MB (which is the default value) for the Edge Controller:
    # inventory/default/group_vars/controller_group/10-default.yml
    
    hugepage_size: "2M"
    hugepage_amount: "1500"
    default_grub_params: "default_hugepagesz= hugepagesz= hugepages="
    
  • To set 10 of the hugepages with the page size of 1GB for the Edge Nodes:
    # inventory/default/group_vars/edgenode_group/10-default.yml
    
    hugepage_size: "1G"
    hugepage_amount: "10"
    default_grub_params: "default_hugepagesz= hugepagesz= hugepages="
    

Customizing hugepages for specific machine

To specify the size or amount only for a specific machine, hugepage_size and/or hugepage_amount can be provided in inventory/default/host_vars/<host_name_from_inventory>/10-default.yml (i.e., if host is named node01, then the file is inventory/default/host_vars/node01/10-default.yml). For example:

# inventory/default/host_vars/node01/10-default.yml

hugepage_size: "2M"
hugepage_amount: "1500"
default_grub_params: "default_hugepagesz= hugepagesz= hugepages="

Reference