8.2. Configuring huge pages on the Compute node

Procedure

1. Configure the amount of huge page memory to reserve on each NUMA node for processes that are not instances:

   parameter_defaults:
     NovaReservedHugePages: ["node:0,size:2048,count:64","node:1,size:1GB,count:1"]

   Where:

   Attribute	Description
   size	The size of the allocated huge page. Valid values: * 2048 (for 2MB) * 1GB
   count	The number of huge pages used by OVS per NUMA node. For example, for 4096 of socket memory used by Open vSwitch, set this to 2.

2. (Optional) To allow instances to allocate 1GB huge pages, configure the CPU feature flags, cpu_model_extra_flags, to include "pdpe1gb":

   parameter_defaults:
      ComputeExtraConfig:
        nova::compute::libvirt::libvirt_cpu_mode: 'custom'
        nova::compute::libvirt::libvirt_cpu_model: 'Haswell-noTSX'
        nova::compute::libvirt::libvirt_cpu_model_extra_flags: 'vmx, pdpe1gb'

   注記
   • CPU feature flags do not need to be configured to allow instances to only request 2 MB huge pages.
   • You can only allocate 1G huge pages to an instance if the host supports 1G huge page allocation.
   • You only need to set cpu_model_extra_flags to pdpe1gb when cpu_mode is set to host-model or custom.
   • If the host supports pdpe1gb, and host-passthrough is used as the cpu_mode, then you do not need to set pdpe1gb as a cpu_model_extra_flags. The pdpe1gb flag is only included in Opteron_G4 and Opteron_G5 CPU models, it is not included in any of the Intel CPU models supported by QEMU.
   • To mitigate for CPU hardware issues, such as Microarchitectural Data Sampling (MDS), you might need to configure other CPU flags. For more information, see RHOS Mitigation for MDS ("Microarchitectural Data Sampling") Security Flaws.

3. To avoid loss of performance after applying Meltdown protection, configure the CPU feature flags, cpu_model_extra_flags, to include "+pcid":

   parameter_defaults:
      ComputeExtraConfig:
        nova::compute::libvirt::libvirt_cpu_mode: 'custom'
        nova::compute::libvirt::libvirt_cpu_model: 'Haswell-noTSX'
        nova::compute::libvirt::libvirt_cpu_model_extra_flags: 'vmx, pdpe1gb, +pcid'

   ヒント

   For more information, see Reducing the performance impact of Meltdown CVE fixes for OpenStack guests with "PCID" CPU feature flag.

4. Add NUMATopologyFilter to the NovaSchedulerDefaultFilters parameter in each Compute environment file, if not already present.

5. Apply this huge page configuration by adding the environment file(s) to your deployment command and deploying the overcloud:

   (undercloud) $ openstack overcloud deploy --templates \
     -e [your environment files]
     -e /home/stack/templates/<compute_environment_file>.yaml