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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
OpenNESS deployment enables hugepages by default and provides parameters for tuning hugepages:
hugepage_size
- size, which can be either2M
or1G
hugepage_amount
- amount
By default, these variables have values:
Mode | Machine type | hugepage_amount |
hugepage_size |
Comments |
---|---|---|---|---|
Network Edge | 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:
group_vars/controller_group/10-default.yml
andgroup_vars/edgenode_group/10-default.yml
will affect Edge Controller and Edge Nodes in every modehost_vars/<inventory_host_name>.yml
will only affect the<inventory_host_name>
host present ininventory.ini
(in all modes)- Hugepages can be also specified for mode and machine type, (e.g., hugepages for On-Premises Edge Node can be set in
network_edge.yml
in a play for Edge Nodes:# network_edge.yml - hosts: edgenode_group vars: hugepage_amount: "5000"
NOTE: Due to Ansible’s* variable precedence, configuring hugepages in
network_edge.yml
is not recommended because it overrides customization ingroup_vars
andhost_vars
. The usage is summarized in the following table:
File | Network Edge | Native On Premises | Edge Controller | Edge Node | Comment |
---|---|---|---|---|---|
group_vars/controller_group/10-default.yml |
yes | yes | yes | ||
group_vars/edgenode_group/10-default.yml |
yes | yes | yes - every node | ||
host_vars/<inventory_host_name>.yml |
yes | yes | yes | yes | affects machine specified in inventory.ini with name <inventory_host_name> |
network_edge.yml |
yes | vars under hosts: controller_group |
vars under hosts: edgenode_group - every node |
not recommended |
Note that variables have precedence:
- not recommended:
network_edge.yml
will always take precedence for files from this list (overrides every other var) host_vars/
group_vars/edgenode_group/10-default.yml
andgroup_vars/controller_group/10-default.yml
group_vars/all/10-default.yml
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 group_vars/edgenode_group/10-default.yml
or 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:
# group_vars/controller_group/10-default.yml hugepage_size: "2M" hugepage_amount: "1500"
- To set 10 of the hugepages with the page size of 1GB for the Edge Nodes:
# group_vars/edgenode_group/10-default.yml hugepage_size: "1G" hugepage_amount: "10"
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 host_vars/<host_name_from_inventory>.yml
(i.e., if host is named node01
, then the file is host_vars/node01.yml
). For example:
# host_vars/node01.yml
hugepage_size: "2M"
hugepage_amount: "1500"