a1a781ddac
This code is being removed as part of an effort to move the pci-irq-affinity-agent into a openstack application container, instead of a platform service. There was a previous change [1] to clean the CentOS builds from the pci affinity agent but it was reverted since it broke the Debian build. Now that the Debian related changes [2] are already merged we can bring this change back. There is still some code in this repo that will be deprecated now that the service will not run on the platform anymore and therefore needs to be removed. This change should clean the repo from unused code related to the pci-irq-affinity-agent and also ensure that the platform will no longer have this service configured and activated. TEST PLAN: PASS: Build the pci-irq-affinity-agent rpm package PASS: Build the pci-irq-affinity-agent wheels PASS: Build the new container image for the agent PASS: Build and Install a platform ISO PASS: Check that the agent service is not present on the platform PASS: Check that the python package was not installed on the platform PASS: Check that the rpm is not present on the platform Story: 2009299 Task: 44607 [1] https://review.opendev.org/c/starlingx/utilities/+/830892 [2] https://review.opendev.org/c/starlingx/utilities/+/840229 Signed-off-by: Thales Elero Cervi <thaleselero.cervi@windriver.com> Change-Id: I8b2286bff66f8e6f85dc0408459103b3b139528d
utilities
This file serves as documentation for the components and features included on the utilities repository.
PCI IRQ Affinity Agent
While in OpenStack it is possible to enable instances to use PCI devices, the interrupts generated by these devices may be handled by host CPUs that are unrelated to the instance, and this can lead to a performance that is lower than it could be if the device interrupts were handled by the instance CPUs.
The agent only acts over instances with dedicated vCPUs. For instances using shared vCPUs no action will be taken by the agent.
The expected outcome from the agent operation is achieving a higher performance by assigning the instances core to handle the interrupts from PCI devices used by these instances and avoid interrupts consuming excessive cycles from the platform cores.
Agent operation
The agent operates by listening to RabbitMQ notifications from Nova. When an instance is created or moved to the host, the agent checks for an specific flavor spec (detailed below) and if it does then it queries libvirt to map the instance vCPUs into pCPUs from the host.
Once the agent has the CPU mapping, it determines the IRQ for each PCI device used by the instance, and then it loops over all PCI devices and determines which host NUMA node is associated with the device, the pCPUs that are associated with the NUMA node and finally set the CPU affinity for the IRQs of the PCI device based on the pCPU list.
There is also a periodic audit that runs every minute and loops over the existing IRQs, so that if there are new IRQs that weren't mapped before the agent maps them, and if there are PCI devices that aren't associated to an instance that they were before, their IRQ affinity is reset to the default value.
Flavor spec
The PCI IRQ Affinity Agent uses a specific flavor spec for PCI interrupt affining, that is used to determine which vCPUs assigned to the instance must handle the interrupts from the PCI devices:
hw:pci_irq_affinity_mask=<vcpus_cpulist>
Where vcpus_cpulist can assume a comma-separated list of
values that can be expressed as:
int: the vCPU expressed byintwill be assigned to handle the interruptions from the PCI devicesint1-int2: the vCPUs betweenint1andint2(inclusive) will be used to handle the interruptions from the PCI devices^int: the vCPU expressed byintwill not be assigned to handle the interruptions from the PCI devices and shall be used to exclude a vCPU that was included in a previous range
NOTE: int must be a value between
0 and flavor.vcpus - 1
Example: hw_pci_irq_affinity_mask=1-4,^3,6 means that
vCPUs with indexes 1,2,4 and 6 from the vCPU list that Nova
allocates to the instance will be assigned to handle interruptions from
the PCI devices.
Limitations
- No CPU affining is performed for instances using shared CPUs (i.e.,
when using flavor spec
hw:cpu_policy=shared) - No CPU affining will be performed when invalid ranges are specified on the flavor spec, the agent instead will log error messages indicating the problem
Agent packaging
The agent code resides on the starlingx/utilities repo,
along with the spec and docker_image files that are used to build a
CentOS image with the agent wheel installed on it.
The agent is deployed by Armada along with the other OpenStack helm
charts; refer to PCI
IRQ Affinity Agent helm chart on
starlingx/openstack-armada-app repository.